-- undo/redo by managing the sequence of events in the current session
-- based on https://github.com/akkartik/mu1/blob/master/edit/012-editor-undo.mu
-- Incredibly inefficient; we make a copy of lines on every single keystroke.
-- The hope here is that we're either editing small files or just reading large files.
-- TODO: highlight stuff inserted by any undo/redo operation
-- TODO: coalesce multiple similar operations
function record_undo_event(State, data)
  State.history[State.next_history] = data
  State.next_history = State.next_history+1
  for i=State.next_history,#State.history do
    State.history[i] = nil
  end
end
function undo_event(State)
  if State.next_history > 1 then
--?     print('moving to history', State.next_history-1)
    State.next_history = State.next_history-1
    local result = State.history[State.next_history]
    return result
  end
end
function redo_event(State)
  if State.next_history <= #State.history then
--?     print('restoring history', State.next_history+1)
    local result = State.history[State.next_history]
    State.next_history = State.next_history+1
    return result
  end
end
-- Copy all relevant global state.
-- Make copies of objects; the rest of the app may mutate them in place, but undo requires immutable histories.
function snapshot(State, s,e)
  -- Snapshot everything by default, but subset if requested.
  assert(s)
  if e == nil then
    e = s
  end
  assert(#State.lines > 0)
  if s < 1 then s = 1 end
  if s > #State.lines then s = #State.lines end
  if e < 1 then e = 1 end
  if e > #State.lines then e = #State.lines end
  -- compare with App.initialize_globals
  local event = {
    screen_top=deepcopy(State.screen_top1),
    selection=deepcopy(State.selection1),
    cursor=deepcopy(State.cursor1),
    lines={},
    start_line=s,
    end_line=e,
    -- no filename; undo history is cleared when filename changes
  }
  -- deep copy lines without cached stuff like text fragments
  for i=s,e do
    local line = State.lines[i]
  end
  return event
end
function patch(lines, from, to)
--?   if #from.lines == 1 and #to.lines == 1 then
--?     assert(from.start_line == from.end_line)
--?     assert(to.start_line == to.end_line)
--?     assert(from.start_line == to.start_line)
--?     lines[from.start_line] = to.lines[1]
--?     return
--?   end
  assert(from.start_line == to.start_line)
  for i=from.end_line,from.start_line,-1 do
    table.remove(lines, i)
  end
  assert(#to.lines == to.end_line-to.start_line+1)
  for i=1,#to.lines do
    table.insert(lines, to.start_line+i-1, to.lines[i])
  end
end
function patch_placeholders(line_cache, from, to)
  assert(from.start_line == to.start_line)
  for i=from.end_line,from.start_line,-1 do
    table.remove(line_cache, i)
  end
  assert(#to.lines == to.end_line-to.start_line+1)
  for i=1,#to.lines do
    table.insert(line_cache, to.start_line+i-1, {})
  end
end
-- https://stackoverflow.com/questions/640642/how-do-you-copy-a-lua-table-by-value/26367080#26367080
function deepcopy(obj, seen)
  if type(obj) ~= 'table' then return obj end
  if seen and seen[obj] then return seen[obj] end
  local s = seen or {}
  local result = setmetatable({}, getmetatable(obj))
  s[obj] = result
  for k,v in pairs(obj) do
    result[deepcopy(k, s)] = deepcopy(v, s)
  end
  return result
end
function minmax(a, b)
  return math.min(a,b), math.max(a,b)
end
    if line.mode == 'text' then
      table.insert(event.lines, {mode='text', data=line.data, dataB=line.dataB})
    elseif line.mode == 'drawing' then
      local points=deepcopy(line.points)
--?       print('copying', line.points, 'with', #line.points, 'points into', points)
      local shapes=deepcopy(line.shapes)
--?       print('copying', line.shapes, 'with', #line.shapes, 'shapes into', shapes)
      table.insert(event.lines, {mode='drawing', h=line.h, points=points, shapes=shapes, pending={}})
--?       table.insert(event.lines, {mode='drawing', h=line.h, points=deepcopy(line.points), shapes=deepcopy(line.shapes), pending={}})
    else
      print(line.mode)
      assert(false)
    end
    current_drawing_mode=Drawing_mode,
    previous_drawing_mode=State.previous_drawing_mode,

end
function icon.hyperlink_decoration(button_params)
  local x,y = button_params.x, button_params.y
  App.color(Hyperlink_decoration_color)
  love.graphics.line(x,y+Editor_state.line_height, x+button_params.w,y+Editor_state.line_height)
end
function icon.freehand(x, y)
  love.graphics.line(x+4,y+7,x+5,y+5)
  love.graphics.line(x+5,y+5,x+7,y+4)
  love.graphics.line(x+7,y+4,x+9,y+3)
  love.graphics.line(x+9,y+3,x+10,y+5)
  love.graphics.line(x+10,y+5,x+12,y+6)
  love.graphics.line(x+12,y+6,x+13,y+8)
  love.graphics.line(x+13,y+8,x+13,y+10)
  love.graphics.line(x+13,y+10,x+14,y+12)
  love.graphics.line(x+14,y+12,x+15,y+14)
  love.graphics.line(x+15,y+14,x+15,y+16)
end
function icon.line(x, y)
  love.graphics.line(x+4,y+2, x+16,y+18)
end
function icon.manhattan(x, y)
  love.graphics.line(x+4,y+20, x+4,y+2)
  love.graphics.line(x+4,y+2, x+10,y+2)
  love.graphics.line(x+10,y+2, x+10,y+10)
  love.graphics.line(x+10,y+10, x+18,y+10)
end
function icon.polygon(x, y)
  love.graphics.line(x+8,y+2, x+14,y+2)
  love.graphics.line(x+14,y+2, x+18,y+10)
  love.graphics.line(x+18,y+10, x+10,y+18)
  love.graphics.line(x+10,y+18, x+4,y+12)
  love.graphics.line(x+4,y+12, x+8,y+2)
end
function icon.rectangle(x, y)
  love.graphics.line(x+4,y+8, x+4,y+16)
  love.graphics.line(x+4,y+16, x+16,y+16)
  love.graphics.line(x+16,y+16, x+16,y+8)
  love.graphics.line(x+16,y+8, x+4,y+8)
end
function icon.square(x, y)
  love.graphics.line(x+6,y+6, x+6,y+16)
  love.graphics.line(x+6,y+16, x+16,y+16)
  love.graphics.line(x+16,y+16, x+16,y+6)
  love.graphics.line(x+16,y+6, x+6,y+6)
end
function icon.circle(x, y)
  love.graphics.circle('line', x+10,y+10, 8)
end
end
function icon.freehand(x, y)
  love.graphics.line(x+4,y+7,x+5,y+5)
  love.graphics.line(x+5,y+5,x+7,y+4)
  love.graphics.line(x+7,y+4,x+9,y+3)
  love.graphics.line(x+9,y+3,x+10,y+5)
  love.graphics.line(x+10,y+5,x+12,y+6)
  love.graphics.line(x+12,y+6,x+13,y+8)
  love.graphics.line(x+13,y+8,x+13,y+10)
  love.graphics.line(x+13,y+10,x+14,y+12)
  love.graphics.line(x+14,y+12,x+15,y+14)
  love.graphics.line(x+15,y+14,x+15,y+16)
end
function icon.line(x, y)
  love.graphics.line(x+4,y+2, x+16,y+18)
end
function icon.manhattan(x, y)
  love.graphics.line(x+4,y+20, x+4,y+2)
  love.graphics.line(x+4,y+2, x+10,y+2)
  love.graphics.line(x+10,y+2, x+10,y+10)
  love.graphics.line(x+10,y+10, x+18,y+10)
end
function icon.polygon(x, y)
  love.graphics.line(x+8,y+2, x+14,y+2)
  love.graphics.line(x+14,y+2, x+18,y+10)
  love.graphics.line(x+18,y+10, x+10,y+18)
  love.graphics.line(x+10,y+18, x+4,y+12)
  love.graphics.line(x+4,y+12, x+8,y+2)
icon = {}
function icon.insert_drawing(button_params)
  local x,y = button_params.x, button_params.y
  App.color(Icon_color)
  love.graphics.rectangle('line', x,y, 12,12)
  love.graphics.line(4,y+6, 16,y+6)
  love.graphics.line(10,y, 10,y+12)

-- helpers for selecting portions of text
-- To keep things simple, we'll ignore the B side when selections start on the
-- A side, and stick to within a single B side selections start in.
-- Return any intersection of the region from State.selection1 to State.cursor1 (or
-- current mouse, if mouse is pressed; or recent mouse if mouse is pressed and
-- currently over a drawing) with the region between {line=line_index, pos=apos}
-- and {line=line_index, pos=bpos}.
-- apos must be less than bpos. However State.selection1 and State.cursor1 can be in any order.
-- Result: positions spos,epos between apos,bpos.
function Text.clip_selection(State, line_index, apos, bpos)
  if State.selection1.line == nil then return nil,nil end
  -- min,max = sorted(State.selection1,State.cursor1)
  local minl,minp = State.selection1.line,State.selection1.pos
  local maxl,maxp
  if App.mouse_down(1) then
    maxl,maxp = Text.mouse_pos(State)
  else
    maxl,maxp = State.cursor1.line,State.cursor1.pos
  end
  if Text.lt1({line=maxl, pos=maxp},
              {line=minl, pos=minp}) then
    minl,maxl = maxl,minl
    minp,maxp = maxp,minp
  end
  -- check if intervals are disjoint
  if line_index < minl then return nil,nil end
  if line_index > maxl then return nil,nil end
  if line_index == minl and bpos <= minp then return nil,nil end
  if line_index == maxl and apos >= maxp then return nil,nil end
  -- compare bounds more carefully (start inclusive, end exclusive)
  local a_ge = Text.le1({line=minl, pos=minp}, {line=line_index, pos=apos})
  local b_lt = Text.lt1({line=line_index, pos=bpos}, {line=maxl, pos=maxp})
--?   print(minl,line_index,maxl, '--', minp,apos,bpos,maxp, '--', a_ge,b_lt)
  if a_ge and b_lt then
    -- fully contained
    return apos,bpos
  elseif a_ge then
    assert(maxl == line_index)
    return apos,maxp
  elseif b_lt then
    assert(minl == line_index)
    return minp,bpos
  else
    assert(minl == maxl and minl == line_index)
    return minp,maxp
  end
end
-- draw highlight for line corresponding to (lo,hi) given an approximate x,y and pos on the same screen line
-- Creates text objects every time, so use this sparingly.
-- Returns some intermediate computation useful elsewhere.
function Text.draw_highlight(State, line, x,y, pos, lo,hi)
  if lo then
    local lo_offset = Text.offset(line.data, lo)
    local hi_offset = Text.offset(line.data, hi)
    local pos_offset = Text.offset(line.data, pos)
    local lo_px
    if pos == lo then
      lo_px = 0
    else
      local before = line.data:sub(pos_offset, lo_offset-1)
      local before_text = App.newText(love.graphics.getFont(), before)
      lo_px = App.width(before_text)
    end
--?     print(lo,pos,hi, '--', lo_offset,pos_offset,hi_offset, '--', lo_px)
    local s = line.data:sub(lo_offset, hi_offset-1)
    local text = App.newText(love.graphics.getFont(), s)
    local text_width = App.width(text)
    App.color(Highlight_color)
    love.graphics.rectangle('fill', x+lo_px,y, text_width,State.line_height)
    App.color(Text_color)
    return lo_px
  end
end
-- inefficient for some reason, so don't do it on every frame
function Text.mouse_pos(State)
  local time = love.timer.getTime()
  if State.recent_mouse.time and State.recent_mouse.time > time-0.1 then
    return State.recent_mouse.line, State.recent_mouse.pos
  end
  State.recent_mouse.time = time
  local line,pos = Text.to_pos(State, App.mouse_x(), App.mouse_y())
  if line then
    State.recent_mouse.line = line
    State.recent_mouse.pos = pos
  end
  return State.recent_mouse.line, State.recent_mouse.pos
end
function Text.to_pos(State, x,y)
  for line_index,line in ipairs(State.lines) do
    if line.mode == 'text' then
      if Text.in_line(State, line_index, x,y) then
        return line_index, Text.to_pos_on_line(State, line_index, x,y)
      end
    end
  end
end
function Text.cut_selection(State)
  if State.selection1.line == nil then return end
  local result = Text.selection(State)
  Text.delete_selection(State)
  return result
end
function Text.delete_selection(State)
  if State.selection1.line == nil then return end
  local minl,maxl = minmax(State.selection1.line, State.cursor1.line)
  local before = snapshot(State, minl, maxl)
  Text.delete_selection_without_undo(State)
  record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
end
function Text.delete_selection_without_undo(State)
  if State.selection1.line == nil then return end
  -- min,max = sorted(State.selection1,State.cursor1)
  local minl,minp = State.selection1.line,State.selection1.pos
  local maxl,maxp = State.cursor1.line,State.cursor1.pos
  if minl > maxl then
    minl,maxl = maxl,minl
    minp,maxp = maxp,minp
  elseif minl == maxl then
    if minp > maxp then
      minp,maxp = maxp,minp
    end
  end
  -- update State.cursor1 and State.selection1
  State.cursor1.line = minl
  State.cursor1.pos = minp
  if Text.lt1(State.cursor1, State.screen_top1) then
    State.screen_top1.line = State.cursor1.line
    State.screen_top1.pos = Text.pos_at_start_of_screen_line(State, State.cursor1)
  end
  State.selection1 = {}
  -- delete everything between min (inclusive) and max (exclusive)
  Text.clear_screen_line_cache(State, minl)
  local min_offset = Text.offset(State.lines[minl].data, minp)
  local max_offset = Text.offset(State.lines[maxl].data, maxp)
  if minl == maxl then
--?     print('minl == maxl')
    State.lines[minl].data = State.lines[minl].data:sub(1, min_offset-1)..State.lines[minl].data:sub(max_offset)
    return
  end
  assert(minl < maxl)
  local rhs = State.lines[maxl].data:sub(max_offset)
  for i=maxl,minl+1,-1 do
    table.remove(State.lines, i)
    table.remove(State.line_cache, i)
  end
  State.lines[minl].data = State.lines[minl].data:sub(1, min_offset-1)..rhs
end
function Text.selection(State)
  if State.selection1.line == nil then return end
  -- min,max = sorted(State.selection1,State.cursor1)
  local minl,minp = State.selection1.line,State.selection1.pos
  local maxl,maxp = State.cursor1.line,State.cursor1.pos
  if minl > maxl then
    minl,maxl = maxl,minl
    minp,maxp = maxp,minp
  elseif minl == maxl then
    if minp > maxp then
      minp,maxp = maxp,minp
    end
  end
  local min_offset = Text.offset(State.lines[minl].data, minp)
  local max_offset = Text.offset(State.lines[maxl].data, maxp)
  if minl == maxl then
    return State.lines[minl].data:sub(min_offset, max_offset-1)
  end
  assert(minl < maxl)
  local result = {State.lines[minl].data:sub(min_offset)}
  for i=minl+1,maxl-1 do
    if State.lines[i].mode == 'text' then
      table.insert(result, State.lines[i].data)
    end
  end
  table.insert(result, State.lines[maxl].data:sub(1, max_offset-1))
  return table.concat(result, '\n')
end

function draw_help_without_mouse_pressed(State, drawing_index)
  local drawing = State.lines[drawing_index]
  local line_cache = State.line_cache[drawing_index]
  App.color(Help_color)
  local y = line_cache.starty+10
  love.graphics.print("Things you can do:", State.left+30,y)
  y = y + State.line_height
  love.graphics.print("* Press the mouse button to start drawing a "..current_shape(State), State.left+30,y)
  y = y + State.line_height
  love.graphics.print("* Hover on a point and press 'ctrl+u' to pick it up and start moving it,", State.left+30,y)
  y = y + State.line_height
  love.graphics.print("then press the mouse button to drop it", State.left+30+bullet_indent(),y)
  y = y + State.line_height
  love.graphics.print("* Hover on a point and press 'ctrl+n', type a name, then press 'enter'", State.left+30,y)
  y = y + State.line_height
  love.graphics.print("* Hover on a point or shape and press 'ctrl+d' to delete it", State.left+30,y)
  y = y + State.line_height
  if State.current_drawing_mode ~= 'freehand' then
    love.graphics.print("* Press 'ctrl+p' to switch to drawing freehand strokes", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'line' then
    love.graphics.print("* Press 'ctrl+l' to switch to drawing lines", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'manhattan' then
    love.graphics.print("* Press 'ctrl+m' to switch to drawing horizontal/vertical lines", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'circle' then
    love.graphics.print("* Press 'ctrl+o' to switch to drawing circles/arcs", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'polygon' then
    love.graphics.print("* Press 'ctrl+g' to switch to drawing polygons", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'rectangle' then
    love.graphics.print("* Press 'ctrl+r' to switch to drawing rectangles", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'square' then
    love.graphics.print("* Press 'ctrl+s' to switch to drawing squares", State.left+30,y)
    y = y + State.line_height
  end
  love.graphics.print("* Press 'ctrl+=' or 'ctrl+-' to zoom in or out, ctrl+0 to reset zoom", State.left+30,y)
  y = y + State.line_height
  love.graphics.print("Press 'esc' now to hide this message", State.left+30,y)
  y = y + State.line_height
  App.color(Help_background_color)
  love.graphics.rectangle('fill', State.left,line_cache.starty, State.width, math.max(Drawing.pixels(drawing.h, State.width),y-line_cache.starty))
end
function draw_help_with_mouse_pressed(State, drawing_index)
  local drawing = State.lines[drawing_index]
  local line_cache = State.line_cache[drawing_index]
  App.color(Help_color)
  local y = line_cache.starty+10
  love.graphics.print("You're currently drawing a "..current_shape(State, drawing.pending), State.left+30,y)
  y = y + State.line_height
  love.graphics.print('Things you can do now:', State.left+30,y)
  y = y + State.line_height
  if State.current_drawing_mode == 'freehand' then
    love.graphics.print('* Release the mouse button to finish drawing the stroke', State.left+30,y)
    y = y + State.line_height
  elseif State.current_drawing_mode == 'line' or State.current_drawing_mode == 'manhattan' then
    love.graphics.print('* Release the mouse button to finish drawing the line', State.left+30,y)
    y = y + State.line_height
  elseif State.current_drawing_mode == 'circle' then
    if drawing.pending.mode == 'circle' then
      love.graphics.print('* Release the mouse button to finish drawing the circle', State.left+30,y)
      y = y + State.line_height
      love.graphics.print("* Press 'a' to draw just an arc of a circle", State.left+30,y)
    else
      love.graphics.print('* Release the mouse button to finish drawing the arc', State.left+30,y)
    end
    y = y + State.line_height
  elseif State.current_drawing_mode == 'polygon' then
    love.graphics.print('* Release the mouse button to finish drawing the polygon', State.left+30,y)
    y = y + State.line_height
    love.graphics.print("* Press 'p' to add a vertex to the polygon", State.left+30,y)
    y = y + State.line_height
  elseif State.current_drawing_mode == 'rectangle' then
    if #drawing.pending.vertices < 2 then
      love.graphics.print("* Press 'p' to add a vertex to the rectangle", State.left+30,y)
      y = y + State.line_height
    else
      love.graphics.print('* Release the mouse button to finish drawing the rectangle', State.left+30,y)
      y = y + State.line_height
      love.graphics.print("* Press 'p' to replace the second vertex of the rectangle", State.left+30,y)
      y = y + State.line_height
    end
  elseif State.current_drawing_mode == 'square' then
    if #drawing.pending.vertices < 2 then
      love.graphics.print("* Press 'p' to add a vertex to the square", State.left+30,y)
      y = y + State.line_height
    else
      love.graphics.print('* Release the mouse button to finish drawing the square', State.left+30,y)
      y = y + State.line_height
      love.graphics.print("* Press 'p' to replace the second vertex of the square", State.left+30,y)
      y = y + State.line_height
    end
  end
  love.graphics.print("* Press 'esc' then release the mouse button to cancel the current shape", State.left+30,y)
  y = y + State.line_height
  y = y + State.line_height
  if State.current_drawing_mode ~= 'line' then
    love.graphics.print("* Press 'l' to switch to drawing lines", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'manhattan' then
    love.graphics.print("* Press 'm' to switch to drawing horizontal/vertical lines", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'circle' then
    love.graphics.print("* Press 'o' to switch to drawing circles/arcs", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'polygon' then
    love.graphics.print("* Press 'g' to switch to drawing polygons", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'rectangle' then
    love.graphics.print("* Press 'r' to switch to drawing rectangles", State.left+30,y)
    y = y + State.line_height
  end
  if State.current_drawing_mode ~= 'square' then
    love.graphics.print("* Press 's' to switch to drawing squares", State.left+30,y)
    y = y + State.line_height
  end
  App.color(Help_background_color)
  love.graphics.rectangle('fill', State.left,line_cache.starty, State.width, math.max(Drawing.pixels(drawing.h, State.width),y-line_cache.starty))
end
function current_shape(State, shape)
  if State.current_drawing_mode == 'freehand' then
    return 'freehand stroke'
  elseif State.current_drawing_mode == 'line' then
    return 'straight line'
  elseif State.current_drawing_mode == 'manhattan' then
    return 'horizontal/vertical line'
  elseif State.current_drawing_mode == 'circle' and shape and shape.start_angle then
    return 'arc'
  else
    return State.current_drawing_mode
  end
end
function bullet_indent()
  return App.width(to_text('* '))
end

geom = {}
function geom.on_shape(x,y, drawing, shape)
  if shape.mode == 'freehand' then
    return geom.on_freehand(x,y, drawing, shape)
  elseif shape.mode == 'line' then
    return geom.on_line(x,y, drawing, shape)
  elseif shape.mode == 'manhattan' then
    local p1 = drawing.points[shape.p1]
    local p2 = drawing.points[shape.p2]
    if p1.x == p2.x then
      if x ~= p1.x then return false end
      local y1,y2 = p1.y, p2.y
      if y1 > y2 then
        y1,y2 = y2,y1
      end
      return y >= y1-2 and y <= y2+2
    elseif p1.y == p2.y then
      if y ~= p1.y then return false end
      local x1,x2 = p1.x, p2.x
      if x1 > x2 then
        x1,x2 = x2,x1
      end
      return x >= x1-2 and x <= x2+2
    end
  elseif shape.mode == 'polygon' or shape.mode == 'rectangle' or shape.mode == 'square' then
    return geom.on_polygon(x,y, drawing, shape)
  elseif shape.mode == 'circle' then
    local center = drawing.points[shape.center]
    local dist = geom.dist(center.x,center.y, x,y)
    return dist > shape.radius*0.95 and dist < shape.radius*1.05
  elseif shape.mode == 'arc' then
    local center = drawing.points[shape.center]
    local dist = geom.dist(center.x,center.y, x,y)
    if dist < shape.radius*0.95 or dist > shape.radius*1.05 then
      return false
    end
    return geom.angle_between(center.x,center.y, x,y, shape.start_angle,shape.end_angle)
  elseif shape.mode == 'deleted' then
  else
    print(shape.mode)
    assert(false)
  end
end
function geom.on_freehand(x,y, drawing, shape)
  local prev
  for _,p in ipairs(shape.points) do
    if prev then
      if geom.on_line(x,y, drawing, {p1=prev, p2=p}) then
        return true
      end
    end
    prev = p
  end
  return false
end
function geom.on_line(x,y, drawing, shape)
  local p1,p2
  if type(shape.p1) == 'number' then
    p1 = drawing.points[shape.p1]
    p2 = drawing.points[shape.p2]
  else
    p1 = shape.p1
    p2 = shape.p2
  end
  if p1.x == p2.x then
    if math.abs(p1.x-x) > 2 then
      return false
    end
    local y1,y2 = p1.y,p2.y
    if y1 > y2 then
      y1,y2 = y2,y1
    end
    return y >= y1-2 and y <= y2+2
  end
  -- has the right slope and intercept
  local m = (p2.y - p1.y) / (p2.x - p1.x)
  local yp = p1.y + m*(x-p1.x)
  if yp < y-2 or yp > y+2 then
    return false
  end
  -- between endpoints
  local k = (x-p1.x) / (p2.x-p1.x)
  return k > -0.005 and k < 1.005
end
function geom.on_polygon(x,y, drawing, shape)
  local prev
  for _,p in ipairs(shape.vertices) do
    if prev then
      if geom.on_line(x,y, drawing, {p1=prev, p2=p}) then
        return true
      end
    end
    prev = p
  end
  return geom.on_line(x,y, drawing, {p1=shape.vertices[1], p2=shape.vertices[#shape.vertices]})
end
-- are (x3,y3) and (x4,y4) on the same side of the line between (x1,y1) and (x2,y2)
function geom.same_side(x1,y1, x2,y2, x3,y3, x4,y4)
  if x1 == x2 then
    return math.sign(x3-x1) == math.sign(x4-x1)
  end
  if y1 == y2 then
    return math.sign(y3-y1) == math.sign(y4-y1)
  end
  local m = (y2-y1)/(x2-x1)
  return math.sign(m*(x3-x1) + y1-y3) == math.sign(m*(x4-x1) + y1-y4)
end
function math.sign(x)
  if x > 0 then
    return 1
  elseif x == 0 then
    return 0
  elseif x < 0 then
    return -1
  end
end
function geom.angle_with_hint(x1, y1, x2, y2, hint)
  local result = geom.angle(x1,y1, x2,y2)
  if hint then
    -- Smooth the discontinuity where angle goes from positive to negative.
    -- The hint is a memory of which way we drew it last time.
    while result > hint+math.pi/10 do
      result = result-math.pi*2
    end
    while result < hint-math.pi/10 do
      result = result+math.pi*2
    end
  end
  return result
end
-- result is from -π/2 to 3π/2, approximately adding math.atan2 from Lua 5.3
-- (LÖVE is Lua 5.1)
function geom.angle(x1,y1, x2,y2)
  local result = math.atan((y2-y1)/(x2-x1))
  if x2 < x1 then
    result = result+math.pi
  end
  return result
end
-- is the line between x,y and cx,cy at an angle between s and e?
function geom.angle_between(ox,oy, x,y, s,e)
  local angle = geom.angle(ox,oy, x,y)
  if s > e then
    s,e = e,s
  end
  -- I'm not sure this is right or ideal..
  angle = angle-math.pi*2
  if s <= angle and angle <= e then
    return true
  end
  angle = angle+math.pi*2
  if s <= angle and angle <= e then
    return true
  end
  angle = angle+math.pi*2
  return s <= angle and angle <= e
end
function geom.dist(x1,y1, x2,y2) return ((x2-x1)^2+(y2-y1)^2)^0.5 end

-- major tests for drawings
-- We minimize assumptions about specific pixels, and try to test at the level
-- of specific shapes. In particular, no tests of freehand drawings.
function test_creating_drawing_saves()
  io.write('\ntest_creating_drawing_saves')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  -- click on button to create drawing
  edit.run_after_mouse_click(Editor_state, 8,Editor_state.top+8, 1)
  -- file not immediately saved
  edit.update(Editor_state, 0.01)
  check_nil(App.filesystem['foo'], 'F - test_creating_drawing_saves/early')
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- filesystem contains drawing and an empty line of text
  check_eq(App.filesystem['foo'], '```lines\n```\n\n', 'F - test_creating_drawing_saves')
end
function test_draw_line()
  io.write('\ntest_draw_line')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  check_eq(#Editor_state.lines, 2, 'F - test_draw_line/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_line/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_line/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_line/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_line/baseline/#shapes')
  -- draw a line
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_line/#shapes')
  check_eq(#drawing.points, 2, 'F - test_draw_line/#points')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_draw_line/shape:1')
  local p1 = drawing.points[drawing.shapes[1].p1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p1.x, 5, 'F - test_draw_line/p1:x')
  check_eq(p1.y, 6, 'F - test_draw_line/p1:y')
  check_eq(p2.x, 35, 'F - test_draw_line/p2:x')
  check_eq(p2.y, 36, 'F - test_draw_line/p2:y')
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- The format on disk isn't perfectly stable. Table fields can be reordered.
  -- So just reload from disk to verify.
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_line/save/#shapes')
  check_eq(#drawing.points, 2, 'F - test_draw_line/save/#points')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_draw_line/save/shape:1')
  local p1 = drawing.points[drawing.shapes[1].p1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p1.x, 5, 'F - test_draw_line/save/p1:x')
  check_eq(p1.y, 6, 'F - test_draw_line/save/p1:y')
  check_eq(p2.x, 35, 'F - test_draw_line/save/p2:x')
  check_eq(p2.y, 36, 'F - test_draw_line/save/p2:y')
end
function test_draw_horizontal_line()
  io.write('\ntest_draw_horizontal_line')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'manhattan'
  edit.draw(Editor_state)
  check_eq(#Editor_state.lines, 2, 'F - test_draw_horizontal_line/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_horizontal_line/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_horizontal_line/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_horizontal_line/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_horizontal_line/baseline/#shapes')
  -- draw a line that is more horizontal than vertical
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+26, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_horizontal_line/#shapes')
  check_eq(#drawing.points, 2, 'F - test_draw_horizontal_line/#points')
  check_eq(drawing.shapes[1].mode, 'manhattan', 'F - test_draw_horizontal_line/shape_mode')
  local p1 = drawing.points[drawing.shapes[1].p1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p1.x, 5, 'F - test_draw_horizontal_line/p1:x')
  check_eq(p1.y, 6, 'F - test_draw_horizontal_line/p1:y')
  check_eq(p2.x, 35, 'F - test_draw_horizontal_line/p2:x')
  check_eq(p2.y, p1.y, 'F - test_draw_horizontal_line/p2:y')
end
function test_draw_circle()
  io.write('\ntest_draw_circle')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  check_eq(#Editor_state.lines, 2, 'F - test_draw_circle/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_circle/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_circle/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_circle/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_circle/baseline/#shapes')
  -- draw a circle
  App.mouse_move(Editor_state.left+4, Editor_state.top+Drawing_padding_top+4)  -- hover on drawing
  edit.run_after_keychord(Editor_state, 'C-o')
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35+30, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_circle/#shapes')
  check_eq(#drawing.points, 1, 'F - test_draw_circle/#points')
  check_eq(drawing.shapes[1].mode, 'circle', 'F - test_draw_horizontal_line/shape_mode')
  check_eq(drawing.shapes[1].radius, 30, 'F - test_draw_circle/radius')
  local center = drawing.points[drawing.shapes[1].center]
  check_eq(center.x, 35, 'F - test_draw_circle/center:x')
  check_eq(center.y, 36, 'F - test_draw_circle/center:y')
end
function test_cancel_stroke()
  io.write('\ntest_cancel_stroke')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  check_eq(#Editor_state.lines, 2, 'F - test_cancel_stroke/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_cancel_stroke/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_cancel_stroke/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_cancel_stroke/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_cancel_stroke/baseline/#shapes')
  -- start drawing a line
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  -- cancel
  edit.run_after_keychord(Editor_state, 'escape')
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 0, 'F - test_cancel_stroke/#shapes')
end
function test_keys_do_not_affect_shape_when_mouse_up()
  io.write('\ntest_keys_do_not_affect_shape_when_mouse_up')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  -- hover over drawing and press 'o' without holding mouse
  App.mouse_move(Editor_state.left+4, Editor_state.top+Drawing_padding_top+4)  -- hover on drawing
  edit.run_after_keychord(Editor_state, 'o')
  -- no change to drawing mode
  check_eq(Editor_state.current_drawing_mode, 'line', 'F - test_keys_do_not_affect_shape_when_mouse_up/drawing_mode')
  -- no change to text either because we didn't run the textinput event
end
function test_draw_circle_mid_stroke()
  io.write('\ntest_draw_circle_mid_stroke')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  check_eq(#Editor_state.lines, 2, 'F - test_draw_circle_mid_stroke/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_circle_mid_stroke/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_circle_mid_stroke/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_circle_mid_stroke/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_circle_mid_stroke/baseline/#shapes')
  -- draw a circle
  App.mouse_move(Editor_state.left+4, Editor_state.top+Drawing_padding_top+4)  -- hover on drawing
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_keychord(Editor_state, 'o')
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35+30, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_circle_mid_stroke/#shapes')
  check_eq(#drawing.points, 1, 'F - test_draw_circle_mid_stroke/#points')
  check_eq(drawing.shapes[1].mode, 'circle', 'F - test_draw_horizontal_line/shape_mode')
  check_eq(drawing.shapes[1].radius, 30, 'F - test_draw_circle_mid_stroke/radius')
  local center = drawing.points[drawing.shapes[1].center]
  check_eq(center.x, 35, 'F - test_draw_circle_mid_stroke/center:x')
  check_eq(center.y, 36, 'F - test_draw_circle_mid_stroke/center:y')
end
function test_draw_arc()
  io.write('\ntest_draw_arc')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'circle'
  edit.draw(Editor_state)
  check_eq(#Editor_state.lines, 2, 'F - test_draw_arc/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_arc/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_arc/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_arc/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_arc/baseline/#shapes')
  -- draw an arc
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  App.mouse_move(Editor_state.left+35+30, Editor_state.top+Drawing_padding_top+36)
  edit.run_after_keychord(Editor_state, 'a')  -- arc mode
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35+50, Editor_state.top+Drawing_padding_top+36+50, 1)  -- 45°
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_arc/#shapes')
  check_eq(#drawing.points, 1, 'F - test_draw_arc/#points')
  check_eq(drawing.shapes[1].mode, 'arc', 'F - test_draw_horizontal_line/shape_mode')
  local arc = drawing.shapes[1]
  check_eq(arc.radius, 30, 'F - test_draw_arc/radius')
  local center = drawing.points[arc.center]
  check_eq(center.x, 35, 'F - test_draw_arc/center:x')
  check_eq(center.y, 36, 'F - test_draw_arc/center:y')
  check_eq(arc.start_angle, 0, 'F - test_draw_arc/start:angle')
  check_eq(arc.end_angle, math.pi/4, 'F - test_draw_arc/end:angle')
end
function test_draw_polygon()
  io.write('\ntest_draw_polygon')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  check_eq(Editor_state.current_drawing_mode, 'line', 'F - test_draw_polygon/baseline/drawing_mode')
  check_eq(#Editor_state.lines, 2, 'F - test_draw_polygon/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_polygon/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_polygon/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_polygon/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_polygon/baseline/#shapes')
  -- first point
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_keychord(Editor_state, 'g')  -- polygon mode
  -- second point
  App.mouse_move(Editor_state.left+65, Editor_state.top+Drawing_padding_top+36)
  edit.run_after_keychord(Editor_state, 'p')  -- add point
  -- final point
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+26, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_polygon/#shapes')
  check_eq(#drawing.points, 3, 'F - test_draw_polygon/vertices')
  local shape = drawing.shapes[1]
  check_eq(shape.mode, 'polygon', 'F - test_draw_polygon/shape_mode')
  check_eq(#shape.vertices, 3, 'F - test_draw_polygon/vertices')
  local p = drawing.points[shape.vertices[1]]
  check_eq(p.x, 5, 'F - test_draw_polygon/p1:x')
  check_eq(p.y, 6, 'F - test_draw_polygon/p1:y')
  local p = drawing.points[shape.vertices[2]]
  check_eq(p.x, 65, 'F - test_draw_polygon/p2:x')
  check_eq(p.y, 36, 'F - test_draw_polygon/p2:y')
  local p = drawing.points[shape.vertices[3]]
  check_eq(p.x, 35, 'F - test_draw_polygon/p3:x')
  check_eq(p.y, 26, 'F - test_draw_polygon/p3:y')
end
function test_draw_rectangle()
  io.write('\ntest_draw_rectangle')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  check_eq(Editor_state.current_drawing_mode, 'line', 'F - test_draw_rectangle/baseline/drawing_mode')
  check_eq(#Editor_state.lines, 2, 'F - test_draw_rectangle/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_rectangle/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_rectangle/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_rectangle/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_rectangle/baseline/#shapes')
  -- first point
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_keychord(Editor_state, 'r')  -- rectangle mode
  -- second point/first edge
  App.mouse_move(Editor_state.left+42, Editor_state.top+Drawing_padding_top+45)
  edit.run_after_keychord(Editor_state, 'p')
  -- override second point/first edge
  App.mouse_move(Editor_state.left+75, Editor_state.top+Drawing_padding_top+76)
  edit.run_after_keychord(Editor_state, 'p')
  -- release (decides 'thickness' of rectangle perpendicular to first edge)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+15, Editor_state.top+Drawing_padding_top+26, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_rectangle/#shapes')
  check_eq(#drawing.points, 5, 'F - test_draw_rectangle/#points')  -- currently includes every point added
  local shape = drawing.shapes[1]
  check_eq(shape.mode, 'rectangle', 'F - test_draw_rectangle/shape_mode')
  check_eq(#shape.vertices, 4, 'F - test_draw_rectangle/vertices')
  local p = drawing.points[shape.vertices[1]]
  check_eq(p.x, 35, 'F - test_draw_rectangle/p1:x')
  check_eq(p.y, 36, 'F - test_draw_rectangle/p1:y')
  local p = drawing.points[shape.vertices[2]]
  check_eq(p.x, 75, 'F - test_draw_rectangle/p2:x')
  check_eq(p.y, 76, 'F - test_draw_rectangle/p2:y')
  local p = drawing.points[shape.vertices[3]]
  check_eq(p.x, 70, 'F - test_draw_rectangle/p3:x')
  check_eq(p.y, 81, 'F - test_draw_rectangle/p3:y')
  local p = drawing.points[shape.vertices[4]]
  check_eq(p.x, 30, 'F - test_draw_rectangle/p4:x')
  check_eq(p.y, 41, 'F - test_draw_rectangle/p4:y')
end
function test_draw_rectangle_intermediate()
  io.write('\ntest_draw_rectangle_intermediate')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  check_eq(Editor_state.current_drawing_mode, 'line', 'F - test_draw_rectangle_intermediate/baseline/drawing_mode')
  check_eq(#Editor_state.lines, 2, 'F - test_draw_rectangle_intermediate/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_rectangle_intermediate/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_rectangle_intermediate/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_rectangle_intermediate/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_rectangle_intermediate/baseline/#shapes')
  -- first point
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_keychord(Editor_state, 'r')  -- rectangle mode
  -- second point/first edge
  App.mouse_move(Editor_state.left+42, Editor_state.top+Drawing_padding_top+45)
  edit.run_after_keychord(Editor_state, 'p')
  -- override second point/first edge
  App.mouse_move(Editor_state.left+75, Editor_state.top+Drawing_padding_top+76)
  edit.run_after_keychord(Editor_state, 'p')
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.points, 3, 'F - test_draw_rectangle_intermediate/#points')  -- currently includes every point added
  local pending = drawing.pending
  check_eq(pending.mode, 'rectangle', 'F - test_draw_rectangle_intermediate/shape_mode')
  check_eq(#pending.vertices, 2, 'F - test_draw_rectangle_intermediate/vertices')
  local p = drawing.points[pending.vertices[1]]
  check_eq(p.x, 35, 'F - test_draw_rectangle_intermediate/p1:x')
  check_eq(p.y, 36, 'F - test_draw_rectangle_intermediate/p1:y')
  local p = drawing.points[pending.vertices[2]]
  check_eq(p.x, 75, 'F - test_draw_rectangle_intermediate/p2:x')
  check_eq(p.y, 76, 'F - test_draw_rectangle_intermediate/p2:y')
  -- outline of rectangle is drawn based on where the mouse is, but we can't check that so far
end
function test_draw_square()
  io.write('\ntest_draw_square')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  check_eq(Editor_state.current_drawing_mode, 'line', 'F - test_draw_square/baseline/drawing_mode')
  check_eq(#Editor_state.lines, 2, 'F - test_draw_square/baseline/#lines')
  check_eq(Editor_state.lines[1].mode, 'drawing', 'F - test_draw_square/baseline/mode')
  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'F - test_draw_square/baseline/y')
  check_eq(Editor_state.lines[1].h, 128, 'F - test_draw_square/baseline/y')
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_draw_square/baseline/#shapes')
  -- first point
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_keychord(Editor_state, 's')  -- square mode
  -- second point/first edge
  App.mouse_move(Editor_state.left+42, Editor_state.top+Drawing_padding_top+45)
  edit.run_after_keychord(Editor_state, 'p')
  -- override second point/first edge
  App.mouse_move(Editor_state.left+65, Editor_state.top+Drawing_padding_top+66)
  edit.run_after_keychord(Editor_state, 'p')
  -- release (decides which side of first edge to draw square on)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+15, Editor_state.top+Drawing_padding_top+26, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_draw_square/#shapes')
  check_eq(#drawing.points, 5, 'F - test_draw_square/#points')  -- currently includes every point added
  check_eq(drawing.shapes[1].mode, 'square', 'F - test_draw_square/shape_mode')
  check_eq(#drawing.shapes[1].vertices, 4, 'F - test_draw_square/vertices')
  local p = drawing.points[drawing.shapes[1].vertices[1]]
  check_eq(p.x, 35, 'F - test_draw_square/p1:x')
  check_eq(p.y, 36, 'F - test_draw_square/p1:y')
  local p = drawing.points[drawing.shapes[1].vertices[2]]
  check_eq(p.x, 65, 'F - test_draw_square/p2:x')
  check_eq(p.y, 66, 'F - test_draw_square/p2:y')
  local p = drawing.points[drawing.shapes[1].vertices[3]]
  check_eq(p.x, 35, 'F - test_draw_square/p3:x')
  check_eq(p.y, 96, 'F - test_draw_square/p3:y')
  local p = drawing.points[drawing.shapes[1].vertices[4]]
  check_eq(p.x, 5, 'F - test_draw_square/p4:x')
  check_eq(p.y, 66, 'F - test_draw_square/p4:y')
end
function test_name_point()
  io.write('\ntest_name_point')
  -- create a drawing with a line
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  -- draw a line
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_name_point/baseline/#shapes')
  check_eq(#drawing.points, 2, 'F - test_name_point/baseline/#points')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_name_point/baseline/shape:1')
  local p1 = drawing.points[drawing.shapes[1].p1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p1.x, 5, 'F - test_name_point/baseline/p1:x')
  check_eq(p1.y, 6, 'F - test_name_point/baseline/p1:y')
  check_eq(p2.x, 35, 'F - test_name_point/baseline/p2:x')
  check_eq(p2.y, 36, 'F - test_name_point/baseline/p2:y')
  check_nil(p2.name, 'F - test_name_point/baseline/p2:name')
  -- enter 'name' mode without moving the mouse
  edit.run_after_keychord(Editor_state, 'C-n')
  check_eq(Editor_state.current_drawing_mode, 'name', 'F - test_name_point/mode:1')
  edit.run_after_textinput(Editor_state, 'A')
  check_eq(p2.name, 'A', 'F - test_name_point')
  -- still in 'name' mode
  check_eq(Editor_state.current_drawing_mode, 'name', 'F - test_name_point/mode:2')
  -- exit 'name' mode
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.current_drawing_mode, 'line', 'F - test_name_point/mode:3')
  check_eq(p2.name, 'A', 'F - test_name_point')
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- change is saved
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  local p2 = Editor_state.lines[1].points[drawing.shapes[1].p2]
  check_eq(p2.name, 'A', 'F - test_name_point/save')
end
function test_move_point()
  io.write('\ntest_move_point')
  -- create a drawing with a line
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_move_point/baseline/#shapes')
  check_eq(#drawing.points, 2, 'F - test_move_point/baseline/#points')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_move_point/baseline/shape:1')
  local p1 = drawing.points[drawing.shapes[1].p1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p1.x, 5, 'F - test_move_point/baseline/p1:x')
  check_eq(p1.y, 6, 'F - test_move_point/baseline/p1:y')
  check_eq(p2.x, 35, 'F - test_move_point/baseline/p2:x')
  check_eq(p2.y, 36, 'F - test_move_point/baseline/p2:y')
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- line is saved to disk
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  local drawing = Editor_state.lines[1]
  local p2 = Editor_state.lines[1].points[drawing.shapes[1].p2]
  check_eq(p2.x, 35, 'F - test_move_point/save/x')
  check_eq(p2.y, 36, 'F - test_move_point/save/y')
  edit.draw(Editor_state)
  -- enter 'move' mode without moving the mouse
  edit.run_after_keychord(Editor_state, 'C-u')
  check_eq(Editor_state.current_drawing_mode, 'move', 'F - test_move_point/mode:1')
  -- point is lifted
  check_eq(drawing.pending.mode, 'move', 'F - test_move_point/mode:2')
  check_eq(drawing.pending.target_point, p2, 'F - test_move_point/target')
  -- move point
  App.mouse_move(Editor_state.left+26, Editor_state.top+Drawing_padding_top+44)
  edit.update(Editor_state, 0.05)
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p2.x, 26, 'F - test_move_point/x')
  check_eq(p2.y, 44, 'F - test_move_point/y')
  -- exit 'move' mode
  edit.run_after_mouse_click(Editor_state, Editor_state.left+26, Editor_state.top+Drawing_padding_top+44, 1)
  check_eq(Editor_state.current_drawing_mode, 'line', 'F - test_move_point/mode:3')
  check_eq(drawing.pending, {}, 'F - test_move_point/pending')
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- change is saved
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  local p2 = Editor_state.lines[1].points[drawing.shapes[1].p2]
  check_eq(p2.x, 26, 'F - test_move_point/save/x')
  check_eq(p2.y, 44, 'F - test_move_point/save/y')
end
function test_move_point_on_manhattan_line()
  io.write('\ntest_move_point_on_manhattan_line')
  -- create a drawing with a manhattan line
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'manhattan'
  edit.draw(Editor_state)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+46, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_move_point_on_manhattan_line/baseline/#shapes')
  check_eq(#drawing.points, 2, 'F - test_move_point_on_manhattan_line/baseline/#points')
  check_eq(drawing.shapes[1].mode, 'manhattan', 'F - test_move_point_on_manhattan_line/baseline/shape:1')
  edit.draw(Editor_state)
  -- enter 'move' mode
  edit.run_after_keychord(Editor_state, 'C-u')
  check_eq(Editor_state.current_drawing_mode, 'move', 'F - test_move_point_on_manhattan_line/mode:1')
  -- move point
  App.mouse_move(Editor_state.left+26, Editor_state.top+Drawing_padding_top+44)
  edit.update(Editor_state, 0.05)
  -- line is no longer manhattan
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_move_point_on_manhattan_line/baseline/shape:1')
end
function test_delete_lines_at_point()
  io.write('\ntest_delete_lines_at_point')
  -- create a drawing with two lines connected at a point
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+55, Editor_state.top+Drawing_padding_top+26, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 2, 'F - test_delete_lines_at_point/baseline/#shapes')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_delete_lines_at_point/baseline/shape:1')
  check_eq(drawing.shapes[2].mode, 'line', 'F - test_delete_lines_at_point/baseline/shape:2')
  -- hover on the common point and delete
  App.mouse_move(Editor_state.left+35, Editor_state.top+Drawing_padding_top+36)
  edit.run_after_keychord(Editor_state, 'C-d')
  check_eq(drawing.shapes[1].mode, 'deleted', 'F - test_delete_lines_at_point/shape:1')
  check_eq(drawing.shapes[2].mode, 'deleted', 'F - test_delete_lines_at_point/shape:2')
  -- wait for some time
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- deleted points disappear after file is reloaded
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  check_eq(#Editor_state.lines[1].shapes, 0, 'F - test_delete_lines_at_point/save')
end
function test_delete_line_under_mouse_pointer()
  io.write('\ntest_delete_line_under_mouse_pointer')
  -- create a drawing with two lines connected at a point
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+55, Editor_state.top+Drawing_padding_top+26, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 2, 'F - test_delete_line_under_mouse_pointer/baseline/#shapes')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_delete_line_under_mouse_pointer/baseline/shape:1')
  check_eq(drawing.shapes[2].mode, 'line', 'F - test_delete_line_under_mouse_pointer/baseline/shape:2')
  -- hover on one of the lines and delete
  App.mouse_move(Editor_state.left+25, Editor_state.top+Drawing_padding_top+26)
  edit.run_after_keychord(Editor_state, 'C-d')
  -- only that line is deleted
  check_eq(drawing.shapes[1].mode, 'deleted', 'F - test_delete_line_under_mouse_pointer/shape:1')
  check_eq(drawing.shapes[2].mode, 'line', 'F - test_delete_line_under_mouse_pointer/shape:2')
end
function test_delete_point_from_polygon()
  io.write('\ntest_delete_point_from_polygon')
  -- create a drawing with two lines connected at a point
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  -- first point
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_keychord(Editor_state, 'g')  -- polygon mode
  -- second point
  App.mouse_move(Editor_state.left+65, Editor_state.top+Drawing_padding_top+36)
  edit.run_after_keychord(Editor_state, 'p')  -- add point
  -- third point
  App.mouse_move(Editor_state.left+35, Editor_state.top+Drawing_padding_top+26)
  edit.run_after_keychord(Editor_state, 'p')  -- add point
  -- fourth point
  edit.run_after_mouse_release(Editor_state, Editor_state.left+14, Editor_state.top+Drawing_padding_top+16, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_delete_point_from_polygon/baseline/#shapes')
  check_eq(drawing.shapes[1].mode, 'polygon', 'F - test_delete_point_from_polygon/baseline/mode')
  check_eq(#drawing.shapes[1].vertices, 4, 'F - test_delete_point_from_polygon/baseline/vertices')
  -- hover on a point and delete
  App.mouse_move(Editor_state.left+35, Editor_state.top+Drawing_padding_top+26)
  edit.run_after_keychord(Editor_state, 'C-d')
  -- just the one point is deleted
  check_eq(drawing.shapes[1].mode, 'polygon', 'F - test_delete_point_from_polygon/shape')
  check_eq(#drawing.shapes[1].vertices, 3, 'F - test_delete_point_from_polygon/vertices')
end
function test_delete_point_from_polygon()
  io.write('\ntest_delete_point_from_polygon')
  -- create a drawing with two lines connected at a point
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  -- first point
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_keychord(Editor_state, 'g')  -- polygon mode
  -- second point
  App.mouse_move(Editor_state.left+65, Editor_state.top+Drawing_padding_top+36)
  edit.run_after_keychord(Editor_state, 'p')  -- add point
  -- third point
  edit.run_after_mouse_release(Editor_state, Editor_state.left+14, Editor_state.top+Drawing_padding_top+16, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_delete_point_from_polygon/baseline/#shapes')
  check_eq(drawing.shapes[1].mode, 'polygon', 'F - test_delete_point_from_polygon/baseline/mode')
  check_eq(#drawing.shapes[1].vertices, 3, 'F - test_delete_point_from_polygon/baseline/vertices')
  -- hover on a point and delete
  App.mouse_move(Editor_state.left+65, Editor_state.top+Drawing_padding_top+36)
  edit.run_after_keychord(Editor_state, 'C-d')
  -- there's < 3 points left, so the whole polygon is deleted
  check_eq(drawing.shapes[1].mode, 'deleted', 'F - test_delete_point_from_polygon')
end
function test_undo_name_point()
  io.write('\ntest_undo_name_point')
  -- create a drawing with a line
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  -- draw a line
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_undo_name_point/baseline/#shapes')
  check_eq(#drawing.points, 2, 'F - test_undo_name_point/baseline/#points')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_undo_name_point/baseline/shape:1')
  local p1 = drawing.points[drawing.shapes[1].p1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p1.x, 5, 'F - test_undo_name_point/baseline/p1:x')
  check_eq(p1.y, 6, 'F - test_undo_name_point/baseline/p1:y')
  check_eq(p2.x, 35, 'F - test_undo_name_point/baseline/p2:x')
  check_eq(p2.y, 36, 'F - test_undo_name_point/baseline/p2:y')
  check_nil(p2.name, 'F - test_undo_name_point/baseline/p2:name')
  check_eq(#Editor_state.history, 1, 'F - test_undo_name_point/baseline/history:1')
--?   print('a', Editor_state.lines.current_drawing)
  -- enter 'name' mode without moving the mouse
  edit.run_after_keychord(Editor_state, 'C-n')
  edit.run_after_textinput(Editor_state, 'A')
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(p2.name, 'A', 'F - test_undo_name_point/baseline')
  check_eq(#Editor_state.history, 3, 'F - test_undo_name_point/baseline/history:2')
  check_eq(Editor_state.next_history, 4, 'F - test_undo_name_point/baseline/next_history')
--?   print('b', Editor_state.lines.current_drawing)
  -- undo
  edit.run_after_keychord(Editor_state, 'C-z')
  local drawing = Editor_state.lines[1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(Editor_state.next_history, 3, 'F - test_undo_name_point/next_history')
  check_eq(p2.name, '', 'F - test_undo_name_point')  -- not quite what it was before, but close enough
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- undo is saved
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  local p2 = Editor_state.lines[1].points[drawing.shapes[1].p2]
  check_eq(p2.name, '', 'F - test_undo_name_point/save')
end
function test_undo_move_point()
  io.write('\ntest_undo_move_point')
  -- create a drawing with a line
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_undo_move_point/baseline/#shapes')
  check_eq(#drawing.points, 2, 'F - test_undo_move_point/baseline/#points')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_undo_move_point/baseline/shape:1')
  local p1 = drawing.points[drawing.shapes[1].p1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p1.x, 5, 'F - test_undo_move_point/baseline/p1:x')
  check_eq(p1.y, 6, 'F - test_undo_move_point/baseline/p1:y')
  check_eq(p2.x, 35, 'F - test_undo_move_point/baseline/p2:x')
  check_eq(p2.y, 36, 'F - test_undo_move_point/baseline/p2:y')
  check_nil(p2.name, 'F - test_undo_move_point/baseline/p2:name')
  -- move p2
  edit.run_after_keychord(Editor_state, 'C-u')
  App.mouse_move(Editor_state.left+26, Editor_state.top+Drawing_padding_top+44)
  edit.update(Editor_state, 0.05)
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(p2.x, 26, 'F - test_undo_move_point/x')
  check_eq(p2.y, 44, 'F - test_undo_move_point/y')
  -- exit 'move' mode
  edit.run_after_mouse_click(Editor_state, Editor_state.left+26, Editor_state.top+Drawing_padding_top+44, 1)
  check_eq(Editor_state.next_history, 4, 'F - test_undo_move_point/next_history')
  -- undo
  edit.run_after_keychord(Editor_state, 'C-z')
  edit.run_after_keychord(Editor_state, 'C-z')  -- bug: need to undo twice
  local drawing = Editor_state.lines[1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(Editor_state.next_history, 2, 'F - test_undo_move_point/next_history')
  check_eq(p2.x, 35, 'F - test_undo_move_point/x')
  check_eq(p2.y, 36, 'F - test_undo_move_point/y')
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- undo is saved
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  local p2 = Editor_state.lines[1].points[drawing.shapes[1].p2]
  check_eq(p2.x, 35, 'F - test_undo_move_point/save/x')
  check_eq(p2.y, 36, 'F - test_undo_move_point/save/y')
end
function test_undo_delete_point()
  io.write('\ntest_undo_delete_point')
  -- create a drawing with two lines connected at a point
  App.screen.init{width=Test_margin_left+256, height=300}  -- drawing coordinates 1:1 with pixels
  Editor_state = edit.initialize_test_state()
  Editor_state.filename = 'foo'
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  Editor_state.current_drawing_mode = 'line'
  edit.draw(Editor_state)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+5, Editor_state.top+Drawing_padding_top+6, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_mouse_press(Editor_state, Editor_state.left+35, Editor_state.top+Drawing_padding_top+36, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+55, Editor_state.top+Drawing_padding_top+26, 1)
  local drawing = Editor_state.lines[1]
  check_eq(#drawing.shapes, 2, 'F - test_undo_delete_point/baseline/#shapes')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_undo_delete_point/baseline/shape:1')
  check_eq(drawing.shapes[2].mode, 'line', 'F - test_undo_delete_point/baseline/shape:2')
  -- hover on the common point and delete
  App.mouse_move(Editor_state.left+35, Editor_state.top+Drawing_padding_top+36)
  edit.run_after_keychord(Editor_state, 'C-d')
  check_eq(drawing.shapes[1].mode, 'deleted', 'F - test_undo_delete_point/shape:1')
  check_eq(drawing.shapes[2].mode, 'deleted', 'F - test_undo_delete_point/shape:2')
  -- undo
  edit.run_after_keychord(Editor_state, 'C-z')
  local drawing = Editor_state.lines[1]
  local p2 = drawing.points[drawing.shapes[1].p2]
  check_eq(Editor_state.next_history, 3, 'F - test_undo_move_point/next_history')
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_undo_delete_point/shape:1')
  check_eq(drawing.shapes[2].mode, 'line', 'F - test_undo_delete_point/shape:2')
  -- wait until save
  App.wait_fake_time(3.1)
  edit.update(Editor_state, 0)
  -- undo is saved
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
  check_eq(#Editor_state.lines[1].shapes, 2, 'F - test_undo_delete_point/save')
end

-- major tests for text editing flows
function test_initial_state()
  io.write('\ntest_initial_state')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  check_eq(#Editor_state.lines, 1, 'F - test_initial_state/#lines')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_initial_state/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_initial_state/cursor:pos')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_initial_state/screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'F - test_initial_state/screen_top:pos')
end
function test_backspace_from_start_of_final_line()
  io.write('\ntest_backspace_from_start_of_final_line')
  -- display final line of text with cursor at start of it
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def'}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.cursor1 = {line=2, pos=1}
  Text.redraw_all(Editor_state)
  -- backspace scrolls up
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(#Editor_state.lines, 1, 'F - test_backspace_from_start_of_final_line/#lines')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_backspace_from_start_of_final_line/cursor')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_backspace_from_start_of_final_line/screen_top')
end
function test_insert_first_character()
  io.write('\ntest_insert_first_character')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  edit.run_after_textinput(Editor_state, 'a')
  local y = Editor_state.top
  App.screen.check(y, 'a', 'F - test_insert_first_character/screen:1')
end
function test_press_ctrl()
  io.write('\ntest_press_ctrl')
  -- press ctrl while the cursor is on text
  App.screen.init{width=50, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{''}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.run_after_keychord(Editor_state, 'C-m')
end
function test_move_left()
  io.write('\ntest_move_left')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'a'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'left')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_move_left')
end
function test_move_right()
  io.write('\ntest_move_right')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'a'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'right')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_move_right')
end
function test_move_left_to_previous_line()
  io.write('\ntest_move_left_to_previous_line')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'left')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_move_left_to_previous_line/line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_move_left_to_previous_line/pos')  -- past end of line
end
function test_move_right_to_next_line()
  io.write('\ntest_move_right_to_next_line')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=4}  -- past end of line
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'right')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_move_right_to_next_line/line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_move_right_to_next_line/pos')
end
function test_move_to_start_of_word()
  io.write('\ntest_move_to_start_of_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=3}
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-left')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_move_to_start_of_word')
end
function test_move_to_start_of_previous_word()
  io.write('\ntest_move_to_start_of_previous_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=4}  -- at the space between words
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-left')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_move_to_start_of_previous_word')
end
function test_skip_to_previous_word()
  io.write('\ntest_skip_to_previous_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=5}  -- at the start of second word
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-left')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_skip_to_previous_word')
end
function test_skip_past_tab_to_previous_word()
  io.write('\ntest_skip_past_tab_to_previous_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def\tghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=10}  -- within third word
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-left')
  check_eq(Editor_state.cursor1.pos, 9, 'F - test_skip_past_tab_to_previous_word')
end
function test_skip_multiple_spaces_to_previous_word()
  io.write('\ntest_skip_multiple_spaces_to_previous_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc  def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=6}  -- at the start of second word
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-left')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_skip_multiple_spaces_to_previous_word')
end
function test_move_to_start_of_word_on_previous_line()
  io.write('\ntest_move_to_start_of_word_on_previous_line')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def', 'ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-left')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_move_to_start_of_word_on_previous_line/line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_move_to_start_of_word_on_previous_line/pos')
end
function test_move_past_end_of_word()
  io.write('\ntest_move_past_end_of_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-right')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_move_past_end_of_word')
end
function test_skip_to_next_word()
  io.write('\ntest_skip_to_next_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=4}  -- at the space between words
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-right')
  check_eq(Editor_state.cursor1.pos, 8, 'F - test_skip_to_next_word')
end
function test_skip_past_tab_to_next_word()
  io.write('\ntest_skip_past_tab_to_next_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc\tdef'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}  -- at the space between words
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-right')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_skip_past_tab_to_next_word')
end
function test_skip_multiple_spaces_to_next_word()
  io.write('\ntest_skip_multiple_spaces_to_next_word')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc  def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=4}  -- at the start of second word
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-right')
  check_eq(Editor_state.cursor1.pos, 9, 'F - test_skip_multiple_spaces_to_next_word')
end
function test_move_past_end_of_word_on_next_line()
  io.write('\ntest_move_past_end_of_word_on_next_line')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def', 'ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=8}
  edit.draw(Editor_state)
  edit.run_after_keychord(Editor_state, 'M-right')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_move_past_end_of_word_on_next_line/line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_move_past_end_of_word_on_next_line/pos')
end
function test_click_with_mouse()
  io.write('\ntest_click_with_mouse')
  -- display two lines with cursor on one of them
  App.screen.init{width=50, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- click on the other line
  edit.draw(Editor_state)
  edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- cursor moves
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_with_mouse/cursor:line')
end
function test_click_with_mouse_to_left_of_line()
  io.write('\ntest_click_with_mouse_to_left_of_line')
  -- display a line with the cursor in the middle
  App.screen.init{width=50, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=3}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- click to the left of the line
  edit.draw(Editor_state)
  edit.run_after_mouse_click(Editor_state, Editor_state.left-4,Editor_state.top+5, 1)
  -- cursor moves to start of line
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_with_mouse_to_left_of_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_click_with_mouse_to_left_of_line/cursor:pos')
end
function test_click_with_mouse_takes_margins_into_account()
  io.write('\ntest_click_with_mouse_takes_margins_into_account')
  -- display two lines with cursor on one of them
  App.screen.init{width=100, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.left = 50  -- occupy only right side of screen
  Editor_state.lines = load_array{'abc', 'def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- click on the other line
  edit.draw(Editor_state)
  edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- cursor moves
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_with_mouse_takes_margins_into_account/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_click_with_mouse_takes_margins_into_account/cursor:pos')
end
function test_click_with_mouse_on_empty_line()
  io.write('\ntest_click_with_mouse_on_empty_line')
  -- display two lines with the first one empty
  App.screen.init{width=50, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'', 'def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- click on the empty line
  edit.draw(Editor_state)
  edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- cursor moves
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_with_mouse_on_empty_line/cursor')
end
function test_draw_text()
  io.write('\ntest_draw_text')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_draw_text/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_draw_text/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_draw_text/screen:3')
end
function test_draw_wrapping_text()
  io.write('\ntest_draw_wrapping_text')
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'defgh', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_draw_wrapping_text/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'de', 'F - test_draw_wrapping_text/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'fgh', 'F - test_draw_wrapping_text/screen:3')
end
function test_draw_word_wrapping_text()
  io.write('\ntest_draw_word_wrapping_text')
  App.screen.init{width=60, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc ', 'F - test_draw_word_wrapping_text/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def ', 'F - test_draw_word_wrapping_text/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_draw_word_wrapping_text/screen:3')
end
function test_click_with_mouse_on_wrapping_line()
  io.write('\ntest_click_with_mouse_on_wrapping_line')
  -- display two lines with cursor on one of them
  App.screen.init{width=50, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def ghi jkl mno pqr stu'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=20}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- click on the other line
  edit.draw(Editor_state)
  edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- cursor moves
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_with_mouse_on_wrapping_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_click_with_mouse_on_wrapping_line/cursor:pos')
end
function test_click_with_mouse_on_wrapping_line_takes_margins_into_account()
  io.write('\ntest_click_with_mouse_on_wrapping_line_takes_margins_into_account')
  -- display two lines with cursor on one of them
  App.screen.init{width=100, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.left = 50  -- occupy only right side of screen
  Editor_state.lines = load_array{'abc def ghi jkl mno pqr stu'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=20}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- click on the other line
  edit.draw(Editor_state)
  edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- cursor moves
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_with_mouse_on_wrapping_line_takes_margins_into_account/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_click_with_mouse_on_wrapping_line_takes_margins_into_account/cursor:pos')
end
function test_draw_text_wrapping_within_word()
  -- arrange a screen line that needs to be split within a word
  io.write('\ntest_draw_text_wrapping_within_word')
  App.screen.init{width=60, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abcd e fghijk', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abcd ', 'F - test_draw_text_wrapping_within_word/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'e fgh', 'F - test_draw_text_wrapping_within_word/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ijk', 'F - test_draw_text_wrapping_within_word/screen:3')
end
function test_draw_wrapping_text_containing_non_ascii()
  -- draw a long line containing non-ASCII
  io.write('\ntest_draw_wrapping_text_containing_non_ascii')
  App.screen.init{width=60, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'madam I’m adam', 'xyz'}  -- notice the non-ASCII apostrophe
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'mad', 'F - test_draw_wrapping_text_containing_non_ascii/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'am I', 'F - test_draw_wrapping_text_containing_non_ascii/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, '’m a', 'F - test_draw_wrapping_text_containing_non_ascii/screen:3')
end
function test_click_on_wrapping_line()
  io.write('\ntest_click_on_wrapping_line')
  -- display a wrapping line
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
                               --  12345678901234
  Editor_state.lines = load_array{"madam I'm adam"}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'madam ', 'F - test_click_on_wrapping_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, "I'm ad", 'F - test_click_on_wrapping_line/baseline/screen:2')
  y = y + Editor_state.line_height
  -- click past end of second screen line
  edit.run_after_mouse_click(Editor_state, App.screen.width-2,y-2, 1)
  -- cursor moves to end of screen line
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_on_wrapping_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 12, 'F - test_click_on_wrapping_line/cursor:pos')
end
function test_click_on_wrapping_line_rendered_from_partway_at_top_of_screen()
  io.write('\ntest_click_on_wrapping_line_rendered_from_partway_at_top_of_screen')
  -- display a wrapping line from its second screen line
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
                               --  12345678901234
  Editor_state.lines = load_array{"madam I'm adam"}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=8}
  Editor_state.screen_top1 = {line=1, pos=7}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, "I'm ad", 'F - test_click_on_wrapping_line_rendered_from_partway_at_top_of_screen/baseline/screen:2')
  y = y + Editor_state.line_height
  -- click past end of second screen line
  edit.run_after_mouse_click(Editor_state, App.screen.width-2,y-2, 1)
  -- cursor moves to end of screen line
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_on_wrapping_line_rendered_from_partway_at_top_of_screen/cursor:line')
  check_eq(Editor_state.cursor1.pos, 12, 'F - test_click_on_wrapping_line_rendered_from_partway_at_top_of_screen/cursor:pos')
end
function test_click_past_end_of_wrapping_line()
  io.write('\ntest_click_past_end_of_wrapping_line')
  -- display a wrapping line
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
                               --  12345678901234
  Editor_state.lines = load_array{"madam I'm adam"}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'madam ', 'F - test_click_past_end_of_wrapping_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, "I'm ad", 'F - test_click_past_end_of_wrapping_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'am', 'F - test_click_past_end_of_wrapping_line/baseline/screen:3')
  y = y + Editor_state.line_height
  -- click past the end of it
  edit.run_after_mouse_click(Editor_state, App.screen.width-2,y-2, 1)
  -- cursor moves to end of line
  check_eq(Editor_state.cursor1.pos, 15, 'F - test_click_past_end_of_wrapping_line/cursor')  -- one more than the number of UTF-8 code-points
end
function test_click_past_end_of_wrapping_line_containing_non_ascii()
  io.write('\ntest_click_past_end_of_wrapping_line_containing_non_ascii')
  -- display a wrapping line containing non-ASCII
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
                               --  12345678901234
  Editor_state.lines = load_array{'madam I’m adam'}  -- notice the non-ASCII apostrophe
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'madam ', 'F - test_click_past_end_of_wrapping_line_containing_non_ascii/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'I’m ad', 'F - test_click_past_end_of_wrapping_line_containing_non_ascii/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'am', 'F - test_click_past_end_of_wrapping_line_containing_non_ascii/baseline/screen:3')
  y = y + Editor_state.line_height
  -- click past the end of it
  edit.run_after_mouse_click(Editor_state, App.screen.width-2,y-2, 1)
  -- cursor moves to end of line
  check_eq(Editor_state.cursor1.pos, 15, 'F - test_click_past_end_of_wrapping_line_containing_non_ascii/cursor')  -- one more than the number of UTF-8 code-points
end
function test_click_past_end_of_word_wrapping_line()
  io.write('\ntest_click_past_end_of_word_wrapping_line')
  -- display a long line wrapping at a word boundary on a screen of more realistic length
  App.screen.init{width=160, height=80}
  Editor_state = edit.initialize_test_state()
                                -- 0        1         2
                                -- 123456789012345678901
  Editor_state.lines = load_array{'the quick brown fox jumped over the lazy dog'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'the quick brown fox ', 'F - test_click_past_end_of_word_wrapping_line/baseline/screen:1')
  y = y + Editor_state.line_height
  -- click past the end of the screen line
  edit.run_after_mouse_click(Editor_state, App.screen.width-2,y-2, 1)
  -- cursor moves to end of screen line
  check_eq(Editor_state.cursor1.pos, 20, 'F - test_click_past_end_of_word_wrapping_line/cursor')
end
function test_edit_wrapping_text()
  io.write('\ntest_edit_wrapping_text')
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=4}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  edit.run_after_textinput(Editor_state, 'g')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_edit_wrapping_text/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'de', 'F - test_edit_wrapping_text/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'fg', 'F - test_edit_wrapping_text/screen:3')
end
function test_insert_newline()
  io.write('\ntest_insert_newline')
  -- display a few lines
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_insert_newline/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_insert_newline/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_insert_newline/baseline/screen:3')
  -- hitting the enter key splits the line
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_insert_newline/screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_insert_newline/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_insert_newline/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'a', 'F - test_insert_newline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'bc', 'F - test_insert_newline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_insert_newline/screen:3')
end
function test_insert_newline_at_start_of_line()
  io.write('\ntest_insert_newline_at_start_of_line')
  -- display a line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- hitting the enter key splits the line
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_insert_newline_at_start_of_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_insert_newline_at_start_of_line/cursor:pos')
  check_eq(Editor_state.lines[1].data, '', 'F - test_insert_newline_at_start_of_line/data:1')
  check_eq(Editor_state.lines[2].data, 'abc', 'F - test_insert_newline_at_start_of_line/data:2')
end
function test_insert_from_clipboard()
  io.write('\ntest_insert_from_clipboard')
  -- display a few lines
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_insert_from_clipboard/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_insert_from_clipboard/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_insert_from_clipboard/baseline/screen:3')
  -- paste some text including a newline, check that new line is created
  App.clipboard = 'xy\nz'
  edit.run_after_keychord(Editor_state, 'C-v')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_insert_from_clipboard/screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_insert_from_clipboard/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_insert_from_clipboard/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'axy', 'F - test_insert_from_clipboard/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'zbc', 'F - test_insert_from_clipboard/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_insert_from_clipboard/screen:3')
end
function test_move_cursor_using_mouse()
  io.write('\ntest_move_cursor_using_mouse')
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
  check_eq(Editor_state.cursor1.line, 1, 'F - test_move_cursor_using_mouse/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_move_cursor_using_mouse/cursor:pos')
end
function test_pagedown()
  io.write('\ntest_pagedown')
  App.screen.init{width=120, height=45}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- initially the first two lines are displayed
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_pagedown/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_pagedown/baseline/screen:2')
  -- after pagedown the bottom line becomes the top
  edit.run_after_keychord(Editor_state, 'pagedown')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_pagedown/screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_pagedown/cursor')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_pagedown/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_pagedown/screen:2')
end
function test_pagedown_can_start_from_middle_of_long_wrapping_line()
  io.write('\ntest_pagedown_can_start_from_middle_of_long_wrapping_line')
  -- draw a few lines starting from a very long wrapping line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def ghi jkl mno pqr stu vwx yza bcd efg hij', 'XYZ'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc ', 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def ', 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/baseline/screen:3')
  -- after pagedown we scroll down the very long wrapping line
  edit.run_after_keychord(Editor_state, 'pagedown')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 9, 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/screen_top:pos')
  y = Editor_state.top
  App.screen.check(y, 'ghi ', 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl ', 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno ', 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/screen:3')
end
function test_pagedown_never_moves_up()
  io.write('\ntest_pagedown_never_moves_up')
  -- draw the final screen line of a wrapping line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=9}
  Editor_state.screen_top1 = {line=1, pos=9}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- pagedown makes no change
  edit.run_after_keychord(Editor_state, 'pagedown')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_pagedown_never_moves_up/screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 9, 'F - test_pagedown_never_moves_up/screen_top:pos')
end
function test_down_arrow_moves_cursor()
  io.write('\ntest_down_arrow_moves_cursor')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- initially the first three lines are displayed
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_down_arrow_moves_cursor/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_down_arrow_moves_cursor/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_down_arrow_moves_cursor/baseline/screen:3')
  -- after hitting the down arrow, the cursor moves down by 1 line
  edit.run_after_keychord(Editor_state, 'down')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_down_arrow_moves_cursor/screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_down_arrow_moves_cursor/cursor')
  -- the screen is unchanged
  y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_down_arrow_moves_cursor/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_down_arrow_moves_cursor/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_down_arrow_moves_cursor/screen:3')
end
function test_down_arrow_scrolls_down_by_one_line()
  io.write('\ntest_down_arrow_scrolls_down_by_one_line')
  -- display the first three lines with the cursor on the bottom line
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_down_arrow_scrolls_down_by_one_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_down_arrow_scrolls_down_by_one_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_down_arrow_scrolls_down_by_one_line/baseline/screen:3')
  -- after hitting the down arrow the screen scrolls down by one line
  edit.run_after_keychord(Editor_state, 'down')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_down_arrow_scrolls_down_by_one_line/screen_top')
  check_eq(Editor_state.cursor1.line, 4, 'F - test_down_arrow_scrolls_down_by_one_line/cursor')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_down_arrow_scrolls_down_by_one_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_down_arrow_scrolls_down_by_one_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_down_arrow_scrolls_down_by_one_line/screen:3')
end
function test_down_arrow_scrolls_down_by_one_screen_line()
  io.write('\ntest_down_arrow_scrolls_down_by_one_screen_line')
  -- display the first three lines with the cursor on the bottom line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_down_arrow_scrolls_down_by_one_screen_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_down_arrow_scrolls_down_by_one_screen_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_down_arrow_scrolls_down_by_one_screen_line/baseline/screen:3')  -- line wrapping includes trailing whitespace
  -- after hitting the down arrow the screen scrolls down by one line
  edit.run_after_keychord(Editor_state, 'down')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_down_arrow_scrolls_down_by_one_screen_line/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_down_arrow_scrolls_down_by_one_screen_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_down_arrow_scrolls_down_by_one_screen_line/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_down_arrow_scrolls_down_by_one_screen_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_down_arrow_scrolls_down_by_one_screen_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_down_arrow_scrolls_down_by_one_screen_line/screen:3')
end
function test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word()
  io.write('\ntest_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word')
  -- display the first three lines with the cursor on the bottom line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghijkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/baseline/screen:3')
  -- after hitting the down arrow the screen scrolls down by one line
  edit.run_after_keychord(Editor_state, 'down')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'F - test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_word/screen:3')
end
function test_page_down_followed_by_down_arrow_does_not_scroll_screen_up()
  io.write('\ntest_page_down_followed_by_down_arrow_does_not_scroll_screen_up')
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghijkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/baseline/screen:3')
  -- after hitting pagedown the screen scrolls down to start of a long line
  edit.run_after_keychord(Editor_state, 'pagedown')
  check_eq(Editor_state.screen_top1.line, 3, 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/baseline2/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/baseline2/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/baseline2/cursor:pos')
  -- after hitting down arrow the screen doesn't scroll down further, and certainly doesn't scroll up
  edit.run_after_keychord(Editor_state, 'down')
  check_eq(Editor_state.screen_top1.line, 3, 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'ghij', 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_page_down_followed_by_down_arrow_does_not_scroll_screen_up/screen:3')
end
function test_up_arrow_moves_cursor()
  io.write('\ntest_up_arrow_moves_cursor')
  -- display the first 3 lines with the cursor on the bottom line
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_up_arrow_moves_cursor/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_up_arrow_moves_cursor/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_up_arrow_moves_cursor/baseline/screen:3')
  -- after hitting the up arrow the cursor moves up by 1 line
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_up_arrow_moves_cursor/screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_up_arrow_moves_cursor/cursor')
  -- the screen is unchanged
  y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_up_arrow_moves_cursor/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_up_arrow_moves_cursor/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_up_arrow_moves_cursor/screen:3')
end
function test_up_arrow_scrolls_up_by_one_line()
  io.write('\ntest_up_arrow_scrolls_up_by_one_line')
  -- display the lines 2/3/4 with the cursor on line 2
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_up_arrow_scrolls_up_by_one_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_up_arrow_scrolls_up_by_one_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_up_arrow_scrolls_up_by_one_line/baseline/screen:3')
  -- after hitting the up arrow the screen scrolls up by one line
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_up_arrow_scrolls_up_by_one_line/screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_up_arrow_scrolls_up_by_one_line/cursor')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_up_arrow_scrolls_up_by_one_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_up_arrow_scrolls_up_by_one_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_up_arrow_scrolls_up_by_one_line/screen:3')
end
function test_up_arrow_scrolls_up_by_one_screen_line()
  io.write('\ntest_up_arrow_scrolls_up_by_one_screen_line')
  -- display lines starting from second screen line of a line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=6}
  Editor_state.screen_top1 = {line=3, pos=5}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'jkl', 'F - test_up_arrow_scrolls_up_by_one_screen_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_up_arrow_scrolls_up_by_one_screen_line/baseline/screen:2')
  -- after hitting the up arrow the screen scrolls up to first screen line
  edit.run_after_keychord(Editor_state, 'up')
  y = Editor_state.top
  App.screen.check(y, 'ghi ', 'F - test_up_arrow_scrolls_up_by_one_screen_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_up_arrow_scrolls_up_by_one_screen_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_up_arrow_scrolls_up_by_one_screen_line/screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'F - test_up_arrow_scrolls_up_by_one_screen_line/screen_top')
  check_eq(Editor_state.screen_top1.pos, 1, 'F - test_up_arrow_scrolls_up_by_one_screen_line/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_up_arrow_scrolls_up_by_one_screen_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_up_arrow_scrolls_up_by_one_screen_line/cursor:pos')
end
function test_up_arrow_scrolls_up_to_final_screen_line()
  io.write('\ntest_up_arrow_scrolls_up_to_final_screen_line')
  -- display lines starting just after a long line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def', 'ghi', 'jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'ghi', 'F - test_up_arrow_scrolls_up_to_final_screen_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_up_arrow_scrolls_up_to_final_screen_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_up_arrow_scrolls_up_to_final_screen_line/baseline/screen:3')
  -- after hitting the up arrow the screen scrolls up to final screen line of previous line
  edit.run_after_keychord(Editor_state, 'up')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen:3')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen_top')
  check_eq(Editor_state.screen_top1.pos, 5, 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_up_arrow_scrolls_up_to_final_screen_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_up_arrow_scrolls_up_to_final_screen_line/cursor:pos')
end
function test_up_arrow_scrolls_up_to_empty_line()
  io.write('\ntest_up_arrow_scrolls_up_to_empty_line')
  -- display a screenful of text with an empty line just above it outside the screen
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'', 'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_up_arrow_scrolls_up_to_empty_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_up_arrow_scrolls_up_to_empty_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_up_arrow_scrolls_up_to_empty_line/baseline/screen:3')
  -- after hitting the up arrow the screen scrolls up by one line
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_up_arrow_scrolls_up_to_empty_line/screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_up_arrow_scrolls_up_to_empty_line/cursor')
  y = Editor_state.top
  -- empty first line
  y = y + Editor_state.line_height
  App.screen.check(y, 'abc', 'F - test_up_arrow_scrolls_up_to_empty_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_up_arrow_scrolls_up_to_empty_line/screen:3')
end
function test_pageup()
  io.write('\ntest_pageup')
  App.screen.init{width=120, height=45}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  -- initially the last two lines are displayed
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_pageup/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_pageup/baseline/screen:2')
  -- after pageup the cursor goes to first line
  edit.run_after_keychord(Editor_state, 'pageup')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_pageup/screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_pageup/cursor')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_pageup/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_pageup/screen:2')
end
function test_pageup_scrolls_up_by_screen_line()
  io.write('\ntest_pageup_scrolls_up_by_screen_line')
  -- display the first three lines with the cursor on the bottom line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def', 'ghi', 'jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'ghi', 'F - test_pageup_scrolls_up_by_screen_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_pageup_scrolls_up_by_screen_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_pageup_scrolls_up_by_screen_line/baseline/screen:3')  -- line wrapping includes trailing whitespace
  -- after hitting the page-up key the screen scrolls up to top
  edit.run_after_keychord(Editor_state, 'pageup')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_pageup_scrolls_up_by_screen_line/screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_pageup_scrolls_up_by_screen_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_pageup_scrolls_up_by_screen_line/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc ', 'F - test_pageup_scrolls_up_by_screen_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_pageup_scrolls_up_by_screen_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_pageup_scrolls_up_by_screen_line/screen:3')
end
function test_pageup_scrolls_up_from_middle_screen_line()
  io.write('\ntest_pageup_scrolls_up_from_middle_screen_line')
  -- display a few lines starting from the middle of a line (Editor_state.cursor1.pos > 1)
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=5}
  Editor_state.screen_top1 = {line=2, pos=5}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'jkl', 'F - test_pageup_scrolls_up_from_middle_screen_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_pageup_scrolls_up_from_middle_screen_line/baseline/screen:3')  -- line wrapping includes trailing whitespace
  -- after hitting the page-up key the screen scrolls up to top
  edit.run_after_keychord(Editor_state, 'pageup')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_pageup_scrolls_up_from_middle_screen_line/screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_pageup_scrolls_up_from_middle_screen_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_pageup_scrolls_up_from_middle_screen_line/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc ', 'F - test_pageup_scrolls_up_from_middle_screen_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_pageup_scrolls_up_from_middle_screen_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_pageup_scrolls_up_from_middle_screen_line/screen:3')
end
function test_enter_on_bottom_line_scrolls_down()
  io.write('\ntest_enter_on_bottom_line_scrolls_down')
  -- display a few lines with cursor on bottom line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_enter_on_bottom_line_scrolls_down/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_enter_on_bottom_line_scrolls_down/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_enter_on_bottom_line_scrolls_down/baseline/screen:3')
  -- after hitting the enter key the screen scrolls down
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_enter_on_bottom_line_scrolls_down/screen_top')
  check_eq(Editor_state.cursor1.line, 4, 'F - test_enter_on_bottom_line_scrolls_down/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_enter_on_bottom_line_scrolls_down/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_enter_on_bottom_line_scrolls_down/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'g', 'F - test_enter_on_bottom_line_scrolls_down/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'hi', 'F - test_enter_on_bottom_line_scrolls_down/screen:3')
end
function test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom()
  io.write('\ntest_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom')
  -- display just the bottom line on screen
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=4, pos=2}
  Editor_state.screen_top1 = {line=4, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'jkl', 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/baseline/screen:1')
  -- after hitting the enter key the screen does not scroll down
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.screen_top1.line, 4, 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen_top')
  check_eq(Editor_state.cursor1.line, 5, 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'j', 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen:2')
end
function test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom()
  io.write('\ntest_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom')
  -- display just an empty bottom line on screen
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', ''}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- after hitting the inserting_text key the screen does not scroll down
  edit.run_after_textinput(Editor_state, 'a')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:pos')
  local y = Editor_state.top
  App.screen.check(y, 'a', 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen:1')
end
function test_typing_on_bottom_line_scrolls_down()
  io.write('\ntest_typing_on_bottom_line_scrolls_down')
  -- display a few lines with cursor on bottom line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=4}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_typing_on_bottom_line_scrolls_down/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_typing_on_bottom_line_scrolls_down/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_typing_on_bottom_line_scrolls_down/baseline/screen:3')
  -- after typing something the line wraps and the screen scrolls down
  edit.run_after_textinput(Editor_state, 'j')
  edit.run_after_textinput(Editor_state, 'k')
  edit.run_after_textinput(Editor_state, 'l')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_typing_on_bottom_line_scrolls_down/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_typing_on_bottom_line_scrolls_down/cursor:line')
  check_eq(Editor_state.cursor1.pos, 7, 'F - test_typing_on_bottom_line_scrolls_down/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_typing_on_bottom_line_scrolls_down/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'F - test_typing_on_bottom_line_scrolls_down/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'F - test_typing_on_bottom_line_scrolls_down/screen:3')
end
function test_left_arrow_scrolls_up_in_wrapped_line()
  io.write('\ntest_left_arrow_scrolls_up_in_wrapped_line')
  -- display lines starting from second screen line of a line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.screen_top1 = {line=3, pos=5}
  Editor_state.screen_bottom1 = {}
  -- cursor is at top of screen
  Editor_state.cursor1 = {line=3, pos=5}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'jkl', 'F - test_left_arrow_scrolls_up_in_wrapped_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_left_arrow_scrolls_up_in_wrapped_line/baseline/screen:2')
  -- after hitting the left arrow the screen scrolls up to first screen line
  edit.run_after_keychord(Editor_state, 'left')
  y = Editor_state.top
  App.screen.check(y, 'ghi ', 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen_top')
  check_eq(Editor_state.screen_top1.pos, 1, 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_left_arrow_scrolls_up_in_wrapped_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_left_arrow_scrolls_up_in_wrapped_line/cursor:pos')
end
function test_right_arrow_scrolls_down_in_wrapped_line()
  io.write('\ntest_right_arrow_scrolls_down_in_wrapped_line')
  -- display the first three lines with the cursor on the bottom line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- cursor is at bottom right of screen
  Editor_state.cursor1 = {line=3, pos=5}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_right_arrow_scrolls_down_in_wrapped_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_right_arrow_scrolls_down_in_wrapped_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_right_arrow_scrolls_down_in_wrapped_line/baseline/screen:3')  -- line wrapping includes trailing whitespace
  -- after hitting the right arrow the screen scrolls down by one line
  edit.run_after_keychord(Editor_state, 'right')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_right_arrow_scrolls_down_in_wrapped_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 6, 'F - test_right_arrow_scrolls_down_in_wrapped_line/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen:3')
end
function test_home_scrolls_up_in_wrapped_line()
  io.write('\ntest_home_scrolls_up_in_wrapped_line')
  -- display lines starting from second screen line of a line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.screen_top1 = {line=3, pos=5}
  Editor_state.screen_bottom1 = {}
  -- cursor is at top of screen
  Editor_state.cursor1 = {line=3, pos=5}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'jkl', 'F - test_home_scrolls_up_in_wrapped_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_home_scrolls_up_in_wrapped_line/baseline/screen:2')
  -- after hitting home the screen scrolls up to first screen line
  edit.run_after_keychord(Editor_state, 'home')
  y = Editor_state.top
  App.screen.check(y, 'ghi ', 'F - test_home_scrolls_up_in_wrapped_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_home_scrolls_up_in_wrapped_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_home_scrolls_up_in_wrapped_line/screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'F - test_home_scrolls_up_in_wrapped_line/screen_top')
  check_eq(Editor_state.screen_top1.pos, 1, 'F - test_home_scrolls_up_in_wrapped_line/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_home_scrolls_up_in_wrapped_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_home_scrolls_up_in_wrapped_line/cursor:pos')
end
function test_end_scrolls_down_in_wrapped_line()
  io.write('\ntest_end_scrolls_down_in_wrapped_line')
  -- display the first three lines with the cursor on the bottom line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- cursor is at bottom right of screen
  Editor_state.cursor1 = {line=3, pos=5}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_end_scrolls_down_in_wrapped_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_end_scrolls_down_in_wrapped_line/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_end_scrolls_down_in_wrapped_line/baseline/screen:3')  -- line wrapping includes trailing whitespace
  -- after hitting end the screen scrolls down by one line
  edit.run_after_keychord(Editor_state, 'end')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_end_scrolls_down_in_wrapped_line/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_end_scrolls_down_in_wrapped_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 8, 'F - test_end_scrolls_down_in_wrapped_line/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_end_scrolls_down_in_wrapped_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'F - test_end_scrolls_down_in_wrapped_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_end_scrolls_down_in_wrapped_line/screen:3')
end
function test_position_cursor_on_recently_edited_wrapping_line()
  -- draw a line wrapping over 2 screen lines
  io.write('\ntest_position_cursor_on_recently_edited_wrapping_line')
  App.screen.init{width=100, height=200}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def ghi jkl mno pqr ', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=25}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc def ghi ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline1/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl mno pqr ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline1/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline1/screen:3')
  -- add to the line until it's wrapping over 3 screen lines
  edit.run_after_textinput(Editor_state, 's')
  edit.run_after_textinput(Editor_state, 't')
  edit.run_after_textinput(Editor_state, 'u')
  check_eq(Editor_state.cursor1.pos, 28, 'F - test_position_cursor_on_recently_edited_wrapping_line/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc def ghi ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline2/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl mno pqr ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline2/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'stu', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline2/screen:3')
  -- try to move the cursor earlier in the third screen line by clicking the mouse
  -- cursor should move
  check_eq(Editor_state.cursor1.line, 1, 'F - test_position_cursor_on_recently_edited_wrapping_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 26, 'F - test_position_cursor_on_recently_edited_wrapping_line/cursor:pos')
end
function test_backspace_can_scroll_up()
  io.write('\ntest_backspace_can_scroll_up')
  -- display the lines 2/3/4 with the cursor on line 2
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_backspace_can_scroll_up/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_backspace_can_scroll_up/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_backspace_can_scroll_up/baseline/screen:3')
  -- after hitting backspace the screen scrolls up by one line
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_backspace_can_scroll_up/screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_backspace_can_scroll_up/cursor')
  y = Editor_state.top
  App.screen.check(y, 'abcdef', 'F - test_backspace_can_scroll_up/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_backspace_can_scroll_up/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_backspace_can_scroll_up/screen:3')
end
function test_backspace_can_scroll_up_screen_line()
  io.write('\ntest_backspace_can_scroll_up_screen_line')
  -- display lines starting from second screen line of a line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=5}
  Editor_state.screen_top1 = {line=3, pos=5}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'jkl', 'F - test_backspace_can_scroll_up_screen_line/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_backspace_can_scroll_up_screen_line/baseline/screen:2')
  -- after hitting backspace the screen scrolls up by one screen line
  edit.run_after_keychord(Editor_state, 'backspace')
  y = Editor_state.top
  App.screen.check(y, 'ghij', 'F - test_backspace_can_scroll_up_screen_line/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'F - test_backspace_can_scroll_up_screen_line/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'F - test_backspace_can_scroll_up_screen_line/screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'F - test_backspace_can_scroll_up_screen_line/screen_top')
  check_eq(Editor_state.screen_top1.pos, 1, 'F - test_backspace_can_scroll_up_screen_line/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_backspace_can_scroll_up_screen_line/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_backspace_can_scroll_up_screen_line/cursor:pos')
end
function test_backspace_past_line_boundary()
  io.write('\ntest_backspace_past_line_boundary')
  -- position cursor at start of a (non-first) line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  -- backspace joins with previous line
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.lines[1].data, 'abcdef', "F - test_backspace_past_line_boundary")
end
function test_undo_insert_text()
  io.write('\ntest_undo_insert_text')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=4}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- insert a character
  edit.draw(Editor_state)
  edit.run_after_textinput(Editor_state, 'g')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_insert_text/baseline/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_undo_insert_text/baseline/cursor:pos')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_undo_insert_text/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'defg', 'F - test_undo_insert_text/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'F - test_undo_insert_text/baseline/screen:3')
  -- undo
  edit.run_after_keychord(Editor_state, 'C-z')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_insert_text/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_undo_insert_text/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_undo_insert_text/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_undo_insert_text/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'F - test_undo_insert_text/screen:3')
end
function test_undo_delete_text()
  io.write('\ntest_undo_delete_text')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'defg', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=5}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  -- delete a character
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_delete_text/baseline/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_undo_delete_text/baseline/cursor:pos')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_undo_delete_text/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'F - test_undo_delete_text/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'F - test_undo_delete_text/baseline/screen:3')
  -- undo
--?   -- after undo, the backspaced key is selected
  edit.run_after_keychord(Editor_state, 'C-z')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_delete_text/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_undo_delete_text/cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_undo_delete_text/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'defg', 'F - test_undo_delete_text/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'F - test_undo_delete_text/screen:3')
end
function test_search()
  io.write('\ntest_search')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- search for a string
  edit.run_after_keychord(Editor_state, 'C-f')
  edit.run_after_textinput(Editor_state, 'd')
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_search/1/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_search/1/cursor:pos')
  -- reset cursor
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  -- search for second occurrence
  edit.run_after_keychord(Editor_state, 'C-f')
  edit.run_after_textinput(Editor_state, 'de')
  edit.run_after_keychord(Editor_state, 'down')
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.cursor1.line, 4, 'F - test_search/2/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_search/2/cursor:pos')
end
function test_search_upwards()
  io.write('\ntest_search_upwards')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc abd'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- search for a string
  edit.run_after_keychord(Editor_state, 'C-f')
  edit.run_after_textinput(Editor_state, 'a')
  -- search for previous occurrence
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_search_upwards/2/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_search_upwards/2/cursor:pos')
end
function test_search_wrap()
  io.write('\ntest_search_wrap')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=3}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- search for a string
  edit.run_after_keychord(Editor_state, 'C-f')
  edit.run_after_textinput(Editor_state, 'a')
  edit.run_after_keychord(Editor_state, 'return')
  -- cursor wraps
  check_eq(Editor_state.cursor1.line, 1, 'F - test_search_wrap/1/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'F - test_search_wrap/1/cursor:pos')
end
function test_search_wrap_upwards()
  io.write('\ntest_search_wrap_upwards')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc abd'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- search upwards for a string
  edit.run_after_keychord(Editor_state, 'C-f')
  edit.run_after_textinput(Editor_state, 'a')
  edit.run_after_keychord(Editor_state, 'up')
  -- cursor wraps
  check_eq(Editor_state.cursor1.line, 1, 'F - test_search_wrap_upwards/1/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'F - test_search_wrap_upwards/1/cursor:pos')
end
  Editor_state.lines = load_array{'```lines', '```', 'def', 'ghi', 'deg'}
function test_undo_restores_selection()
  io.write('\ntest_undo_restores_selection')
  -- display a line of text with some part selected
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.selection1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- delete selected text
  edit.run_after_textinput(Editor_state, 'x')
  check_eq(Editor_state.lines[1].data, 'xbc', 'F - test_undo_restores_selection/baseline')
  check_nil(Editor_state.selection1.line, 'F - test_undo_restores_selection/baseline:selection')
  -- undo
  edit.run_after_keychord(Editor_state, 'C-z')
  edit.run_after_keychord(Editor_state, 'C-z')
  -- selection is restored
  check_eq(Editor_state.selection1.line, 1, 'F - test_undo_restores_selection/line')
  check_eq(Editor_state.selection1.pos, 2, 'F - test_undo_restores_selection/pos')
end
  check_nil(Editor_state.selection1.line, 'F - test_undo_delete_text/selection:line')
  check_nil(Editor_state.selection1.pos, 'F - test_undo_delete_text/selection:pos')
--?   check_eq(Editor_state.selection1.line, 2, 'F - test_undo_delete_text/selection:line')
--?   check_eq(Editor_state.selection1.pos, 4, 'F - test_undo_delete_text/selection:pos')
  check_nil(Editor_state.selection1.line, 'F - test_undo_delete_text/baseline/selection:line')
  check_nil(Editor_state.selection1.pos, 'F - test_undo_delete_text/baseline/selection:pos')
  check_nil(Editor_state.selection1.line, 'F - test_undo_insert_text/selection:line')
  check_nil(Editor_state.selection1.pos, 'F - test_undo_insert_text/selection:pos')
  check_nil(Editor_state.selection1.line, 'F - test_undo_insert_text/baseline/selection:line')
  check_nil(Editor_state.selection1.pos, 'F - test_undo_insert_text/baseline/selection:pos')
-- some tests for operating over selections created using Shift- chords
-- we're just testing delete_selection, and it works the same for all keys
function test_backspace_over_selection()
  io.write('\ntest_backspace_over_selection')
  -- select just one character within a line with cursor before selection
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.selection1 = {line=1, pos=2}
  -- backspace deletes the selected character, even though it's after the cursor
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.lines[1].data, 'bc', "F - test_backspace_over_selection/data")
  -- cursor (remains) at start of selection
  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_over_selection/cursor:line")
  check_eq(Editor_state.cursor1.pos, 1, "F - test_backspace_over_selection/cursor:pos")
  -- selection is cleared
  check_nil(Editor_state.selection1.line, "F - test_backspace_over_selection/selection")
end
function test_backspace_over_selection_reverse()
  io.write('\ntest_backspace_over_selection_reverse')
  -- select just one character within a line with cursor after selection
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.selection1 = {line=1, pos=1}
  -- backspace deletes the selected character
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.lines[1].data, 'bc', "F - test_backspace_over_selection_reverse/data")
  -- cursor moves to start of selection
  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_over_selection_reverse/cursor:line")
  check_eq(Editor_state.cursor1.pos, 1, "F - test_backspace_over_selection_reverse/cursor:pos")
  -- selection is cleared
  check_nil(Editor_state.selection1.line, "F - test_backspace_over_selection_reverse/selection")
end
function test_backspace_over_multiple_lines()
  io.write('\ntest_backspace_over_multiple_lines')
  -- select just one character within a line with cursor after selection
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.selection1 = {line=4, pos=2}
  -- backspace deletes the region and joins the remaining portions of lines on either side
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.lines[1].data, 'akl', "F - test_backspace_over_multiple_lines/data:1")
  check_eq(Editor_state.lines[2].data, 'mno', "F - test_backspace_over_multiple_lines/data:2")
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_over_multiple_lines/cursor:line")
  check_eq(Editor_state.cursor1.pos, 2, "F - test_backspace_over_multiple_lines/cursor:pos")
  -- selection is cleared
  check_nil(Editor_state.selection1.line, "F - test_backspace_over_multiple_lines/selection")
end
function test_backspace_to_end_of_line()
  io.write('\ntest_backspace_to_end_of_line')
  -- select region from cursor to end of line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.selection1 = {line=1, pos=4}
  -- backspace deletes rest of line without joining to any other line
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.lines[1].data, 'a', "F - test_backspace_to_start_of_line/data:1")
  check_eq(Editor_state.lines[2].data, 'def', "F - test_backspace_to_start_of_line/data:2")
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_to_start_of_line/cursor:line")
  check_eq(Editor_state.cursor1.pos, 2, "F - test_backspace_to_start_of_line/cursor:pos")
  -- selection is cleared
  check_nil(Editor_state.selection1.line, "F - test_backspace_to_start_of_line/selection")
end
function test_backspace_to_start_of_line()
  io.write('\ntest_backspace_to_start_of_line')
  -- select region from cursor to start of line
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.selection1 = {line=2, pos=3}
  -- backspace deletes beginning of line without joining to any other line
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(Editor_state.lines[1].data, 'abc', "F - test_backspace_to_start_of_line/data:1")
  check_eq(Editor_state.lines[2].data, 'f', "F - test_backspace_to_start_of_line/data:2")
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 2, "F - test_backspace_to_start_of_line/cursor:line")
  check_eq(Editor_state.cursor1.pos, 1, "F - test_backspace_to_start_of_line/cursor:pos")
  -- selection is cleared
  check_nil(Editor_state.selection1.line, "F - test_backspace_to_start_of_line/selection")
end
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+Editor_state.line_height*2+5, 1)
end
function test_pagedown_skips_drawings()
  io.write('\ntest_pagedown_skips_drawings')
  -- some lines of text with a drawing intermixed
  local drawing_width = 50
  App.screen.init{width=Editor_state.left+drawing_width, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc',               -- height 15
                                  '```lines', '```',   -- height 25
                                  'def',               -- height 15
                                  'ghi'}               -- height 15
  Text.redraw_all(Editor_state)
  check_eq(Editor_state.lines[2].mode, 'drawing', 'F - test_pagedown_skips_drawings/baseline/lines')
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  local drawing_height = Drawing_padding_height + drawing_width/2  -- default
  -- initially the screen displays the first line and the drawing
  -- 15px margin + 15px line1 + 10px margin + 25px drawing + 10px margin = 75px < screen height 80px
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'F - test_pagedown_skips_drawings/baseline/screen:1')
  -- after pagedown the screen draws the drawing up top
  -- 15px margin + 10px margin + 25px drawing + 10px margin + 15px line3 = 75px < screen height 80px
  edit.run_after_keychord(Editor_state, 'pagedown')
  check_eq(Editor_state.screen_top1.line, 2, 'F - test_pagedown_skips_drawings/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'F - test_pagedown_skips_drawings/cursor')
  y = Editor_state.top + drawing_height
  App.screen.check(y, 'def', 'F - test_pagedown_skips_drawings/screen:1')
function test_cut_without_selection()
  io.write('\ntest_cut_without_selection')
  -- display a few lines
  App.screen.init{width=Editor_state.left+30, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  Editor_state.selection1 = {}
  edit.draw(Editor_state)
  -- try to cut without selecting text
  edit.run_after_keychord(Editor_state, 'C-x')
  -- no crash
  check_nil(Editor_state.selection1.line, 'F - test_cut_without_selection')
end
  check_nil(Editor_state.selection1.line, 'F - test_move_cursor_using_mouse/selection:line')
  check_nil(Editor_state.selection1.pos, 'F - test_move_cursor_using_mouse/selection:pos')
end
function test_select_text_using_mouse()
  io.write('\ntest_select_text_using_mouse')
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  Editor_state.selection1 = {}
  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
  -- press and hold on first location
  edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- drag and release somewhere else
  edit.run_after_mouse_release(Editor_state, Editor_state.left+20,Editor_state.top+Editor_state.line_height+5, 1)
  check_eq(Editor_state.selection1.line, 1, 'F - test_select_text_using_mouse/selection:line')
  check_eq(Editor_state.selection1.pos, 2, 'F - test_select_text_using_mouse/selection:pos')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_select_text_using_mouse/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_select_text_using_mouse/cursor:pos')
end
function test_select_text_using_mouse_and_shift()
  io.write('\ntest_select_text_using_mouse_and_shift')
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  Editor_state.selection1 = {}
  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
  -- click on first location
  edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- hold down shift and click somewhere else
  App.fake_key_press('lshift')
  edit.run_after_mouse_press(Editor_state, Editor_state.left+20,Editor_state.top+5, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+20,Editor_state.top+Editor_state.line_height+5, 1)
  App.fake_key_release('lshift')
  check_eq(Editor_state.selection1.line, 1, 'F - test_select_text_using_mouse_and_shift/selection:line')
  check_eq(Editor_state.selection1.pos, 2, 'F - test_select_text_using_mouse_and_shift/selection:pos')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_select_text_using_mouse_and_shift/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'F - test_select_text_using_mouse_and_shift/cursor:pos')
end
function test_select_text_repeatedly_using_mouse_and_shift()
  io.write('\ntest_select_text_repeatedly_using_mouse_and_shift')
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
  Text.redraw_all(Editor_state)
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  Editor_state.selection1 = {}
  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
  -- click on first location
  edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- hold down shift and click on a second location
  App.fake_key_press('lshift')
  edit.run_after_mouse_press(Editor_state, Editor_state.left+20,Editor_state.top+5, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+20,Editor_state.top+Editor_state.line_height+5, 1)
  -- hold down shift and click at a third location
  App.fake_key_press('lshift')
  edit.run_after_mouse_press(Editor_state, Editor_state.left+20,Editor_state.top+5, 1)
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+Editor_state.line_height+5, 1)
  App.fake_key_release('lshift')
  -- selection is between first and third location. forget the second location, not the first.
  check_eq(Editor_state.selection1.line, 1, 'F - test_select_text_repeatedly_using_mouse_and_shift/selection:line')
  check_eq(Editor_state.selection1.pos, 2, 'F - test_select_text_repeatedly_using_mouse_and_shift/selection:pos')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_select_text_repeatedly_using_mouse_and_shift/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_select_text_repeatedly_using_mouse_and_shift/cursor:pos')
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  Editor_state.selection1 = {}
function test_edit_deletes_selection()
  io.write('\ntest_edit_deletes_selection')
  -- display a line of text with some part selected
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.selection1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- press a key
  edit.run_after_textinput(Editor_state, 'x')
  -- selected text is deleted and replaced with the key
  check_eq(Editor_state.lines[1].data, 'xbc', 'F - test_edit_deletes_selection')
end
function test_edit_with_shift_key_deletes_selection()
  io.write('\ntest_edit_with_shift_key_deletes_selection')
  -- display a line of text with some part selected
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.selection1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- mimic precise keypresses for a capital letter
  App.fake_key_press('lshift')
  edit.keychord_pressed(Editor_state, 'd', 'd')
  edit.textinput(Editor_state, 'D')
  edit.key_released(Editor_state, 'd')
  App.fake_key_release('lshift')
  -- selected text is deleted and replaced with the key
  check_nil(Editor_state.selection1.line, 'F - test_edit_with_shift_key_deletes_selection')
  check_eq(Editor_state.lines[1].data, 'Dbc', 'F - test_edit_with_shift_key_deletes_selection/data')
end
function test_copy_does_not_reset_selection()
  io.write('\ntest_copy_does_not_reset_selection')
  -- display a line of text with a selection
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.selection1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- copy selection
  edit.run_after_keychord(Editor_state, 'C-c')
  check_eq(App.clipboard, 'a', 'F - test_copy_does_not_reset_selection/clipboard')
  -- selection is reset since shift key is not pressed
  check(Editor_state.selection1.line, 'F - test_copy_does_not_reset_selection')
end
function test_cut()
  io.write('\ntest_cut')
  -- display a line of text with some part selected
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.selection1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- press a key
  edit.run_after_keychord(Editor_state, 'C-x')
  check_eq(App.clipboard, 'a', 'F - test_cut/clipboard')
  -- selected text is deleted
  check_eq(Editor_state.lines[1].data, 'bc', 'F - test_cut/data')
end
function test_paste_replaces_selection()
  io.write('\ntest_paste_replaces_selection')
  -- display a line of text with a selection
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, pos=1}
  Editor_state.selection1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- set clipboard
  App.clipboard = 'xyz'
  -- paste selection
  edit.run_after_keychord(Editor_state, 'C-v')
  -- selection is reset since shift key is not pressed
  -- selection includes the newline, so it's also deleted
  check_eq(Editor_state.lines[1].data, 'xyzdef', 'F - test_paste_replaces_selection')
end
function test_deleting_selection_may_scroll()
  io.write('\ntest_deleting_selection_may_scroll')
  -- display lines 2/3/4
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=2}
  Editor_state.screen_top1 = {line=2, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'def', 'F - test_deleting_selection_may_scroll/baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'F - test_deleting_selection_may_scroll/baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'F - test_deleting_selection_may_scroll/baseline/screen:3')
  -- set up a selection starting above the currently displayed page
  Editor_state.selection1 = {line=1, pos=2}
  -- delete selection
  edit.run_after_keychord(Editor_state, 'backspace')
  -- page scrolls up
  check_eq(Editor_state.screen_top1.line, 1, 'F - test_deleting_selection_may_scroll')
  check_eq(Editor_state.lines[1].data, 'ahi', 'F - test_deleting_selection_may_scroll/data')
end
end
function test_select_text()
  io.write('\ntest_select_text')
  -- display a line of text
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc def'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- select a letter
  App.fake_key_press('lshift')
  edit.run_after_keychord(Editor_state, 'S-right')
  App.fake_key_release('lshift')
  edit.key_released(Editor_state, 'lshift')
  -- selection persists even after shift is released
  check_eq(Editor_state.selection1.line, 1, 'F - test_select_text/selection:line')
  check_eq(Editor_state.selection1.pos, 1, 'F - test_select_text/selection:pos')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_select_text/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_select_text/cursor:pos')
end
function test_cursor_movement_without_shift_resets_selection()
  io.write('\ntest_cursor_movement_without_shift_resets_selection')
  -- display a line of text with some part selected
  App.screen.init{width=75, height=80}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.selection1 = {line=1, pos=2}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  -- press an arrow key without shift
  edit.run_after_keychord(Editor_state, 'right')
  -- no change to data, selection is reset
  check_nil(Editor_state.selection1.line, 'F - test_cursor_movement_without_shift_resets_selection')
  check_eq(Editor_state.lines[1].data, 'abc', 'F - test_cursor_movement_without_shift_resets_selection/data')
  check_nil(Editor_state.selection1.line, 'F - test_click_with_mouse_on_wrapping_line_takes_margins_into_account/selection is empty to avoid perturbing future edits')
  check_nil(Editor_state.selection1.line, 'F - test_click_with_mouse_on_wrapping_line/selection is empty to avoid perturbing future edits')
  check_nil(Editor_state.selection1.line, 'F - test_click_with_mouse_takes_margins_into_account/selection is empty to avoid perturbing future edits')
  check_nil(Editor_state.selection1.line, 'F - test_click_with_mouse_to_left_of_line/selection is empty to avoid perturbing future edits')
  check_nil(Editor_state.selection1.line, 'F - test_click_with_mouse/selection is empty to avoid perturbing future edits')
end
function test_click_to_create_drawing()
  io.write('\ntest_click_to_create_drawing')
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{}
  Text.redraw_all(Editor_state)
  edit.draw(Editor_state)
  edit.run_after_mouse_click(Editor_state, 8,Editor_state.top+8, 1)
  -- cursor skips drawing to always remain on text
  check_eq(#Editor_state.lines, 2, 'F - test_click_to_create_drawing/#lines')
  check_eq(Editor_state.cursor1.line, 2, 'F - test_click_to_create_drawing/cursor')
end
function test_backspace_to_delete_drawing()
  io.write('\ntest_backspace_to_delete_drawing')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'```lines', '```', ''}
  Text.redraw_all(Editor_state)
  -- cursor is on text as always (outside tests this will get initialized correctly)
  Editor_state.cursor1.line = 2
  -- backspacing deletes the drawing
  edit.run_after_keychord(Editor_state, 'backspace')
  check_eq(#Editor_state.lines, 1, 'F - test_backspace_to_delete_drawing/#lines')
  check_eq(Editor_state.cursor1.line, 1, 'F - test_backspace_to_delete_drawing/cursor')

-- primitives for editing drawings
Drawing = {}
require 'drawing_tests'
-- All drawings span 100% of some conceptual 'page width' and divide it up
-- into 256 parts.
function Drawing.draw(State, line_index, y)
  local line = State.lines[line_index]
  local line_cache = State.line_cache[line_index]
  line_cache.starty = y
  local pmx,pmy = App.mouse_x(), App.mouse_y()
  if pmx < State.right and pmy > line_cache.starty and pmy < line_cache.starty+Drawing.pixels(line.h, State.width) then
    App.color(Icon_color)
    love.graphics.rectangle('line', State.left,line_cache.starty, State.width,Drawing.pixels(line.h, State.width))
    if icon[State.current_drawing_mode] then
      icon[State.current_drawing_mode](State.right-22, line_cache.starty+4)
    else
      icon[State.previous_drawing_mode](State.right-22, line_cache.starty+4)
    end
    if App.mouse_down(1) and love.keyboard.isDown('h') then
      draw_help_with_mouse_pressed(State, line_index)
      return
    end
  end
  if line.show_help then
    draw_help_without_mouse_pressed(State, line_index)
    return
  end
  local mx = Drawing.coord(pmx-State.left, State.width)
  local my = Drawing.coord(pmy-line_cache.starty, State.width)
  for _,shape in ipairs(line.shapes) do
    assert(shape)
    if geom.on_shape(mx,my, line, shape) then
      App.color(Focus_stroke_color)
    else
      App.color(Stroke_color)
    end
    Drawing.draw_shape(line, shape, line_cache.starty, State.left,State.right)
  end
  local function px(x) return Drawing.pixels(x, State.width)+State.left end
  local function py(y) return Drawing.pixels(y, State.width)+line_cache.starty end
  for i,p in ipairs(line.points) do
    if p.deleted == nil then
      if Drawing.near(p, mx,my, State.width) then
        App.color(Focus_stroke_color)
        love.graphics.circle('line', px(p.x),py(p.y), Same_point_distance)
      else
        App.color(Stroke_color)
        love.graphics.circle('fill', px(p.x),py(p.y), 2)
      end
      if p.name then
        -- TODO: clip
        local x,y = px(p.x)+5, py(p.y)+5
        love.graphics.print(p.name, x,y)
        if State.current_drawing_mode == 'name' and i == line.pending.target_point then
          -- create a faint red box for the name
          App.color(Current_name_background_color)
          local name_text
          -- TODO: avoid computing name width on every repaint
          if p.name == '' then
            name_text = State.em
          else
            name_text = App.newText(love.graphics.getFont(), p.name)
          end
          love.graphics.rectangle('fill', x,y, App.width(name_text), State.line_height)
        end
      end
    end
  end
  App.color(Current_stroke_color)
  Drawing.draw_pending_shape(line, line_cache.starty, State.left,State.right)
end
function Drawing.draw_shape(drawing, shape, top, left,right)
  local width = right-left
  local function px(x) return Drawing.pixels(x, width)+left end
  local function py(y) return Drawing.pixels(y, width)+top end
  if shape.mode == 'freehand' then
    local prev = nil
    for _,point in ipairs(shape.points) do
      if prev then
        love.graphics.line(px(prev.x),py(prev.y), px(point.x),py(point.y))
      end
      prev = point
    end
  elseif shape.mode == 'line' or shape.mode == 'manhattan' then
    local p1 = drawing.points[shape.p1]
    local p2 = drawing.points[shape.p2]
    love.graphics.line(px(p1.x),py(p1.y), px(p2.x),py(p2.y))
  elseif shape.mode == 'polygon' or shape.mode == 'rectangle' or shape.mode == 'square' then
    local prev = nil
    for _,point in ipairs(shape.vertices) do
      local curr = drawing.points[point]
      if prev then
        love.graphics.line(px(prev.x),py(prev.y), px(curr.x),py(curr.y))
      end
      prev = curr
    end
    -- close the loop
    local curr = drawing.points[shape.vertices[1]]
    love.graphics.line(px(prev.x),py(prev.y), px(curr.x),py(curr.y))
  elseif shape.mode == 'circle' then
    -- TODO: clip
    local center = drawing.points[shape.center]
    love.graphics.circle('line', px(center.x),py(center.y), Drawing.pixels(shape.radius, width))
  elseif shape.mode == 'arc' then
    local center = drawing.points[shape.center]
    love.graphics.arc('line', 'open', px(center.x),py(center.y), Drawing.pixels(shape.radius, width), shape.start_angle, shape.end_angle, 360)
  elseif shape.mode == 'deleted' then
    -- ignore
  else
    print(shape.mode)
    assert(false)
  end
end
function Drawing.draw_pending_shape(drawing, top, left,right)
  local width = right-left
  local pmx,pmy = App.mouse_x(), App.mouse_y()
  local function px(x) return Drawing.pixels(x, width)+left end
  local function py(y) return Drawing.pixels(y, width)+top end
  local mx = Drawing.coord(pmx-left, width)
  local my = Drawing.coord(pmy-top, width)
  -- recreate pixels from coords to precisely mimic how the drawing will look
  -- after mouse_released
  pmx,pmy = px(mx), py(my)
  local shape = drawing.pending
  if shape.mode == nil then
    -- nothing pending
  elseif shape.mode == 'freehand' then
    local shape_copy = deepcopy(shape)
    Drawing.smoothen(shape_copy)
    Drawing.draw_shape(drawing, shape_copy, top, left,right)
  elseif shape.mode == 'line' then
    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
      return
    end
    local p1 = drawing.points[shape.p1]
    love.graphics.line(px(p1.x),py(p1.y), pmx,pmy)
  elseif shape.mode == 'manhattan' then
    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
      return
    end
    local p1 = drawing.points[shape.p1]
    if math.abs(mx-p1.x) > math.abs(my-p1.y) then
      love.graphics.line(px(p1.x),py(p1.y), pmx,     py(p1.y))
    else
      love.graphics.line(px(p1.x),py(p1.y), px(p1.x),pmy)
    end
  elseif shape.mode == 'polygon' then
    -- don't close the loop on a pending polygon
    local prev = nil
    for _,point in ipairs(shape.vertices) do
      local curr = drawing.points[point]
      if prev then
        love.graphics.line(px(prev.x),py(prev.y), px(curr.x),py(curr.y))
      end
      prev = curr
    end
    love.graphics.line(px(prev.x),py(prev.y), pmx,pmy)
  elseif shape.mode == 'rectangle' then
    local first = drawing.points[shape.vertices[1]]
    if #shape.vertices == 1 then
      love.graphics.line(px(first.x),py(first.y), pmx,pmy)
      return
    end
    local second = drawing.points[shape.vertices[2]]
    local thirdx,thirdy, fourthx,fourthy = Drawing.complete_rectangle(first.x,first.y, second.x,second.y, mx,my)
    love.graphics.line(px(first.x),py(first.y), px(second.x),py(second.y))
    love.graphics.line(px(second.x),py(second.y), px(thirdx),py(thirdy))
    love.graphics.line(px(thirdx),py(thirdy), px(fourthx),py(fourthy))
    love.graphics.line(px(fourthx),py(fourthy), px(first.x),py(first.y))
  elseif shape.mode == 'square' then
    local first = drawing.points[shape.vertices[1]]
    if #shape.vertices == 1 then
      love.graphics.line(px(first.x),py(first.y), pmx,pmy)
      return
    end
    local second = drawing.points[shape.vertices[2]]
    local thirdx,thirdy, fourthx,fourthy = Drawing.complete_square(first.x,first.y, second.x,second.y, mx,my)
    love.graphics.line(px(first.x),py(first.y), px(second.x),py(second.y))
    love.graphics.line(px(second.x),py(second.y), px(thirdx),py(thirdy))
    love.graphics.line(px(thirdx),py(thirdy), px(fourthx),py(fourthy))
    love.graphics.line(px(fourthx),py(fourthy), px(first.x),py(first.y))
  elseif shape.mode == 'circle' then
    local center = drawing.points[shape.center]
    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
      return
    end
    local cx,cy = px(center.x), py(center.y)
    love.graphics.circle('line', cx,cy, geom.dist(cx,cy, App.mouse_x(),App.mouse_y()))
  elseif shape.mode == 'arc' then
    local center = drawing.points[shape.center]
    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
      return
    end
    shape.end_angle = geom.angle_with_hint(center.x,center.y, mx,my, shape.end_angle)
    local cx,cy = px(center.x), py(center.y)
    love.graphics.arc('line', 'open', cx,cy, Drawing.pixels(shape.radius, width), shape.start_angle, shape.end_angle, 360)
  elseif shape.mode == 'move' then
    -- nothing pending; changes are immediately committed
  elseif shape.mode == 'name' then
    -- nothing pending; changes are immediately committed
  else
    print(shape.mode)
    assert(false)
  end
end
function Drawing.in_drawing(drawing, line_cache, x,y, left,right)
  if line_cache.starty == nil then return false end  -- outside current page
  local width = right-left
  return y >= line_cache.starty and y < line_cache.starty + Drawing.pixels(drawing.h, width) and x >= left and x < right
end
function Drawing.mouse_pressed(State, drawing_index, x,y, mouse_button)
  local drawing = State.lines[drawing_index]
  local line_cache = State.line_cache[drawing_index]
  local cx = Drawing.coord(x-State.left, State.width)
  local cy = Drawing.coord(y-line_cache.starty, State.width)
  if State.current_drawing_mode == 'freehand' then
    drawing.pending = {mode=State.current_drawing_mode, points={{x=cx, y=cy}}}
  elseif State.current_drawing_mode == 'line' or State.current_drawing_mode == 'manhattan' then
    local j = Drawing.find_or_insert_point(drawing.points, cx, cy, State.width)
    drawing.pending = {mode=State.current_drawing_mode, p1=j}
  elseif State.current_drawing_mode == 'polygon' or State.current_drawing_mode == 'rectangle' or State.current_drawing_mode == 'square' then
    local j = Drawing.find_or_insert_point(drawing.points, cx, cy, State.width)
    drawing.pending = {mode=State.current_drawing_mode, vertices={j}}
  elseif State.current_drawing_mode == 'circle' then
    local j = Drawing.find_or_insert_point(drawing.points, cx, cy, State.width)
    drawing.pending = {mode=State.current_drawing_mode, center=j}
  elseif State.current_drawing_mode == 'move' then
    -- all the action is in mouse_released
  elseif State.current_drawing_mode == 'name' then
    -- nothing
  else
    print(State.current_drawing_mode)
    assert(false)
  end
end
-- a couple of operations on drawings need to constantly check the state of the mouse
function Drawing.update(State)
  if State.lines.current_drawing == nil then return end
  local drawing = State.lines.current_drawing
  local line_cache = State.line_cache[State.lines.current_drawing_index]
  assert(drawing.mode == 'drawing')
  local pmx, pmy = App.mouse_x(), App.mouse_y()
  local mx = Drawing.coord(pmx-State.left, State.width)
  local my = Drawing.coord(pmy-line_cache.starty, State.width)
  if App.mouse_down(1) then
    if Drawing.in_drawing(drawing, line_cache, pmx,pmy, State.left,State.right) then
      if drawing.pending.mode == 'freehand' then
        table.insert(drawing.pending.points, {x=mx, y=my})
      elseif drawing.pending.mode == 'move' then
        drawing.pending.target_point.x = mx
        drawing.pending.target_point.y = my
        Drawing.relax_constraints(drawing, drawing.pending.target_point_index)
      end
    end
  elseif State.current_drawing_mode == 'move' then
    if Drawing.in_drawing(drawing, line_cache, pmx, pmy, State.left,State.right) then
      drawing.pending.target_point.x = mx
      drawing.pending.target_point.y = my
      Drawing.relax_constraints(drawing, drawing.pending.target_point_index)
    end
  else
    -- do nothing
  end
end
function Drawing.relax_constraints(drawing, p)
  for _,shape in ipairs(drawing.shapes) do
    if shape.mode == 'manhattan' then
      if shape.p1 == p then
        shape.mode = 'line'
      elseif shape.p2 == p then
        shape.mode = 'line'
      end
    elseif shape.mode == 'rectangle' or shape.mode == 'square' then
      for _,v in ipairs(shape.vertices) do
        if v == p then
          shape.mode = 'polygon'
        end
      end
    end
  end
end
function Drawing.mouse_released(State, x,y, mouse_button)
  if State.current_drawing_mode == 'move' then
    State.current_drawing_mode = State.previous_drawing_mode
    State.previous_drawing_mode = nil
    if State.lines.current_drawing then
      State.lines.current_drawing.pending = {}
      State.lines.current_drawing = nil
    end
  elseif State.lines.current_drawing then
    local drawing = State.lines.current_drawing
    local line_cache = State.line_cache[State.lines.current_drawing_index]
    if drawing.pending then
      if drawing.pending.mode == nil then
        -- nothing pending
      elseif drawing.pending.mode == 'freehand' then
        -- the last point added during update is good enough
        Drawing.smoothen(drawing.pending)
        table.insert(drawing.shapes, drawing.pending)
      elseif drawing.pending.mode == 'line' then
        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
        if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
          drawing.pending.p2 = Drawing.find_or_insert_point(drawing.points, mx,my, State.width)
          table.insert(drawing.shapes, drawing.pending)
        end
      elseif drawing.pending.mode == 'manhattan' then
        local p1 = drawing.points[drawing.pending.p1]
        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
        if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
          if math.abs(mx-p1.x) > math.abs(my-p1.y) then
            drawing.pending.p2 = Drawing.find_or_insert_point(drawing.points, mx, p1.y, State.width)
          else
            drawing.pending.p2 = Drawing.find_or_insert_point(drawing.points, p1.x, my, State.width)
          end
          local p2 = drawing.points[drawing.pending.p2]
          App.mouse_move(State.left+Drawing.pixels(p2.x, State.width), line_cache.starty+Drawing.pixels(p2.y, State.width))
          table.insert(drawing.shapes, drawing.pending)
        end
      elseif drawing.pending.mode == 'polygon' then
        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
        if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
          table.insert(drawing.pending.vertices, Drawing.find_or_insert_point(drawing.points, mx,my, State.width))
          table.insert(drawing.shapes, drawing.pending)
        end
      elseif drawing.pending.mode == 'rectangle' then
        assert(#drawing.pending.vertices <= 2)
        if #drawing.pending.vertices == 2 then
          local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
          if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
            local first = drawing.points[drawing.pending.vertices[1]]
            local second = drawing.points[drawing.pending.vertices[2]]
            local thirdx,thirdy, fourthx,fourthy = Drawing.complete_rectangle(first.x,first.y, second.x,second.y, mx,my)
            table.insert(drawing.pending.vertices, Drawing.find_or_insert_point(drawing.points, thirdx,thirdy, State.width))
            table.insert(drawing.pending.vertices, Drawing.find_or_insert_point(drawing.points, fourthx,fourthy, State.width))
            table.insert(drawing.shapes, drawing.pending)
          end
        else
          -- too few points; draw nothing
        end
      elseif drawing.pending.mode == 'square' then
        assert(#drawing.pending.vertices <= 2)
        if #drawing.pending.vertices == 2 then
          local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
          if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
            local first = drawing.points[drawing.pending.vertices[1]]
            local second = drawing.points[drawing.pending.vertices[2]]
            local thirdx,thirdy, fourthx,fourthy = Drawing.complete_square(first.x,first.y, second.x,second.y, mx,my)
            table.insert(drawing.pending.vertices, Drawing.find_or_insert_point(drawing.points, thirdx,thirdy, State.width))
            table.insert(drawing.pending.vertices, Drawing.find_or_insert_point(drawing.points, fourthx,fourthy, State.width))
            table.insert(drawing.shapes, drawing.pending)
          end
        end
      elseif drawing.pending.mode == 'circle' then
        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
        if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
          local center = drawing.points[drawing.pending.center]
          drawing.pending.radius = round(geom.dist(center.x,center.y, mx,my))
          table.insert(drawing.shapes, drawing.pending)
        end
      elseif drawing.pending.mode == 'arc' then
        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
        if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
          local center = drawing.points[drawing.pending.center]
          drawing.pending.end_angle = geom.angle_with_hint(center.x,center.y, mx,my, drawing.pending.end_angle)
          table.insert(drawing.shapes, drawing.pending)
        end
      elseif drawing.pending.mode == 'name' then
        -- drop it
      else
        print(drawing.pending.mode)
        assert(false)
      end
      State.lines.current_drawing.pending = {}
      State.lines.current_drawing = nil
    end
  end
end
function Drawing.keychord_pressed(State, chord)
  if chord == 'C-p' and not App.mouse_down(1) then
    State.current_drawing_mode = 'freehand'
  elseif App.mouse_down(1) and chord == 'l' then
    State.current_drawing_mode = 'line'
    local _,drawing = Drawing.current_drawing(State)
    if drawing.pending.mode == 'freehand' then
      drawing.pending.p1 = Drawing.find_or_insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y, State.width)
    elseif drawing.pending.mode == 'polygon' or drawing.pending.mode == 'rectangle' or drawing.pending.mode == 'square' then
      drawing.pending.p1 = drawing.pending.vertices[1]
    elseif drawing.pending.mode == 'circle' or drawing.pending.mode == 'arc' then
      drawing.pending.p1 = drawing.pending.center
    end
    drawing.pending.mode = 'line'
  elseif chord == 'C-l' and not App.mouse_down(1) then
    State.current_drawing_mode = 'line'
  elseif App.mouse_down(1) and chord == 'm' then
    State.current_drawing_mode = 'manhattan'
    local drawing = Drawing.select_drawing_at_mouse(State)
    if drawing.pending.mode == 'freehand' then
      drawing.pending.p1 = Drawing.find_or_insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y, State.width)
    elseif drawing.pending.mode == 'line' then
      -- do nothing
    elseif drawing.pending.mode == 'polygon' or drawing.pending.mode == 'rectangle' or drawing.pending.mode == 'square' then
      drawing.pending.p1 = drawing.pending.vertices[1]
    elseif drawing.pending.mode == 'circle' or drawing.pending.mode == 'arc' then
      drawing.pending.p1 = drawing.pending.center
    end
    drawing.pending.mode = 'manhattan'
  elseif chord == 'C-m' and not App.mouse_down(1) then
    State.current_drawing_mode = 'manhattan'
  elseif chord == 'C-g' and not App.mouse_down(1) then
    State.current_drawing_mode = 'polygon'
  elseif App.mouse_down(1) and chord == 'g' then
    State.current_drawing_mode = 'polygon'
    local _,drawing = Drawing.current_drawing(State)
    if drawing.pending.mode == 'freehand' then
      drawing.pending.vertices = {Drawing.find_or_insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y, State.width)}
    elseif drawing.pending.mode == 'line' or drawing.pending.mode == 'manhattan' then
      if drawing.pending.vertices == nil then
        drawing.pending.vertices = {drawing.pending.p1}
      end
    elseif drawing.pending.mode == 'rectangle' or drawing.pending.mode == 'square' then
      -- reuse existing vertices
    elseif drawing.pending.mode == 'circle' or drawing.pending.mode == 'arc' then
      drawing.pending.vertices = {drawing.pending.center}
    end
    drawing.pending.mode = 'polygon'
  elseif chord == 'C-r' and not App.mouse_down(1) then
    State.current_drawing_mode = 'rectangle'
  elseif App.mouse_down(1) and chord == 'r' then
    State.current_drawing_mode = 'rectangle'
    local _,drawing = Drawing.current_drawing(State)
    if drawing.pending.mode == 'freehand' then
      drawing.pending.vertices = {Drawing.find_or_insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y, State.width)}
    elseif drawing.pending.mode == 'line' or drawing.pending.mode == 'manhattan' then
      if drawing.pending.vertices == nil then
        drawing.pending.vertices = {drawing.pending.p1}
      end
    elseif drawing.pending.mode == 'polygon' or drawing.pending.mode == 'square' then
      -- reuse existing (1-2) vertices
    elseif drawing.pending.mode == 'circle' or drawing.pending.mode == 'arc' then
      drawing.pending.vertices = {drawing.pending.center}
    end
    drawing.pending.mode = 'rectangle'
  elseif chord == 'C-s' and not App.mouse_down(1) then
    State.current_drawing_mode = 'square'
  elseif App.mouse_down(1) and chord == 's' then
    State.current_drawing_mode = 'square'
    local _,drawing = Drawing.current_drawing(State)
    if drawing.pending.mode == 'freehand' then
      drawing.pending.vertices = {Drawing.find_or_insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y, State.width)}
    elseif drawing.pending.mode == 'line' or drawing.pending.mode == 'manhattan' then
      if drawing.pending.vertices == nil then
        drawing.pending.vertices = {drawing.pending.p1}
      end
    elseif drawing.pending.mode == 'polygon' then
      while #drawing.pending.vertices > 2 do
        table.remove(drawing.pending.vertices)
      end
    elseif drawing.pending.mode == 'rectangle' then
      -- reuse existing (1-2) vertices
    elseif drawing.pending.mode == 'circle' or drawing.pending.mode == 'arc' then
      drawing.pending.vertices = {drawing.pending.center}
    end
    drawing.pending.mode = 'square'
  elseif App.mouse_down(1) and chord == 'p' and State.current_drawing_mode == 'polygon' then
    local _,drawing,line_cache = Drawing.current_drawing(State)
    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-line_cache.starty, State.width)
    local j = Drawing.find_or_insert_point(drawing.points, mx,my, State.width)
    table.insert(drawing.pending.vertices, j)
  elseif App.mouse_down(1) and chord == 'p' and (State.current_drawing_mode == 'rectangle' or State.current_drawing_mode == 'square') then
    local _,drawing,line_cache = Drawing.current_drawing(State)
    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-line_cache.starty, State.width)
    local j = Drawing.find_or_insert_point(drawing.points, mx,my, State.width)
    while #drawing.pending.vertices >= 2 do
      table.remove(drawing.pending.vertices)
    end
    table.insert(drawing.pending.vertices, j)
  elseif chord == 'C-o' and not App.mouse_down(1) then
    State.current_drawing_mode = 'circle'
  elseif App.mouse_down(1) and chord == 'a' and State.current_drawing_mode == 'circle' then
    local _,drawing,line_cache = Drawing.current_drawing(State)
    drawing.pending.mode = 'arc'
    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-line_cache.starty, State.width)
    local center = drawing.points[drawing.pending.center]
    drawing.pending.radius = round(geom.dist(center.x,center.y, mx,my))
    drawing.pending.start_angle = geom.angle(center.x,center.y, mx,my)
  elseif App.mouse_down(1) and chord == 'o' then
    State.current_drawing_mode = 'circle'
    local _,drawing = Drawing.current_drawing(State)
    if drawing.pending.mode == 'freehand' then
      drawing.pending.center = Drawing.find_or_insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y, State.width)
    elseif drawing.pending.mode == 'line' or drawing.pending.mode == 'manhattan' then
      drawing.pending.center = drawing.pending.p1
    elseif drawing.pending.mode == 'polygon' or drawing.pending.mode == 'rectangle' or drawing.pending.mode == 'square' then
      drawing.pending.center = drawing.pending.vertices[1]
    end
    drawing.pending.mode = 'circle'
  elseif chord == 'C-u' and not App.mouse_down(1) then
    local drawing_index,drawing,line_cache,i,p = Drawing.select_point_at_mouse(State)
    if drawing then
      if State.previous_drawing_mode == nil then
        State.previous_drawing_mode = State.current_drawing_mode
      end
      State.current_drawing_mode = 'move'
      drawing.pending = {mode=State.current_drawing_mode, target_point=p, target_point_index=i}
      State.lines.current_drawing_index = drawing_index
      State.lines.current_drawing = drawing
    end
  elseif chord == 'C-n' and not App.mouse_down(1) then
    local drawing_index,drawing,line_cache,point_index,p = Drawing.select_point_at_mouse(State)
    if drawing then
      if State.previous_drawing_mode == nil then
        -- don't clobber
        State.previous_drawing_mode = State.current_drawing_mode
      end
      State.current_drawing_mode = 'name'
      p.name = ''
      drawing.pending = {mode=State.current_drawing_mode, target_point=point_index}
      State.lines.current_drawing_index = drawing_index
      State.lines.current_drawing = drawing
    end
  elseif chord == 'C-d' and not App.mouse_down(1) then
    local _,drawing,_,i,p = Drawing.select_point_at_mouse(State)
    if drawing then
      for _,shape in ipairs(drawing.shapes) do
        if Drawing.contains_point(shape, i) then
          if shape.mode == 'polygon' then
            local idx = table.find(shape.vertices, i)
            assert(idx)
            table.remove(shape.vertices, idx)
            if #shape.vertices < 3 then
              shape.mode = 'deleted'
            end
          else
            shape.mode = 'deleted'
          end
        end
      end
      drawing.points[i].deleted = true
    end
    local drawing,_,_,shape = Drawing.select_shape_at_mouse(State)
    if drawing then
      shape.mode = 'deleted'
    end
  elseif chord == 'C-h' and not App.mouse_down(1) then
    local drawing = Drawing.select_drawing_at_mouse(State)
    if drawing then
      drawing.show_help = true
    end
  elseif chord == 'escape' and App.mouse_down(1) then
    local _,drawing = Drawing.current_drawing(State)
    drawing.pending = {}
  end
end
function Drawing.complete_rectangle(firstx,firsty, secondx,secondy, x,y)
  if firstx == secondx then
    return x,secondy, x,firsty
  end
  if firsty == secondy then
    return secondx,y, firstx,y
  end
  local first_slope = (secondy-firsty)/(secondx-firstx)
  -- slope of second edge:
  --    -1/first_slope
  -- equation of line containing the second edge:
  --    y-secondy = -1/first_slope*(x-secondx)
  -- => 1/first_slope*x + y + (- secondy - secondx/first_slope) = 0
  -- now we want to find the point on this line that's closest to the mouse pointer.
  -- https://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line#Line_defined_by_an_equation
  local a = 1/first_slope
  local c = -secondy - secondx/first_slope
  local thirdx = round(((x-a*y) - a*c) / (a*a + 1))
  local thirdy = round((a*(-x + a*y) - c) / (a*a + 1))
  -- slope of third edge = first_slope
  -- equation of line containing third edge:
  --     y - thirdy = first_slope*(x-thirdx)
  --  => -first_slope*x + y + (-thirdy + thirdx*first_slope) = 0
  -- now we want to find the point on this line that's closest to the first point
  local a = -first_slope
  local c = -thirdy + thirdx*first_slope
  local fourthx = round(((firstx-a*firsty) - a*c) / (a*a + 1))
  local fourthy = round((a*(-firstx + a*firsty) - c) / (a*a + 1))
  return thirdx,thirdy, fourthx,fourthy
end
function Drawing.complete_square(firstx,firsty, secondx,secondy, x,y)
  -- use x,y only to decide which side of the first edge to complete the square on
  local deltax = secondx-firstx
  local deltay = secondy-firsty
  local thirdx = secondx+deltay
  local thirdy = secondy-deltax
  if not geom.same_side(firstx,firsty, secondx,secondy, thirdx,thirdy, x,y) then
    deltax = -deltax
    deltay = -deltay
    thirdx = secondx+deltay
    thirdy = secondy-deltax
  end
  local fourthx = firstx+deltay
  local fourthy = firsty-deltax
  return thirdx,thirdy, fourthx,fourthy
end
function Drawing.current_drawing(State)
  local x, y = App.mouse_x(), App.mouse_y()
  for drawing_index,drawing in ipairs(State.lines) do
    if drawing.mode == 'drawing' then
      local line_cache = State.line_cache[drawing_index]
      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
        return drawing_index,drawing,line_cache
      end
    end
  end
  return nil
end
function Drawing.select_shape_at_mouse(State)
  for drawing_index,drawing in ipairs(State.lines) do
    if drawing.mode == 'drawing' then
      local x, y = App.mouse_x(), App.mouse_y()
      local line_cache = State.line_cache[drawing_index]
      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
        for i,shape in ipairs(drawing.shapes) do
          assert(shape)
          if geom.on_shape(mx,my, drawing, shape) then
            return drawing,line_cache,i,shape
          end
        end
      end
    end
  end
end
function Drawing.select_point_at_mouse(State)
  for drawing_index,drawing in ipairs(State.lines) do
    if drawing.mode == 'drawing' then
      local x, y = App.mouse_x(), App.mouse_y()
      local line_cache = State.line_cache[drawing_index]
      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
        for i,point in ipairs(drawing.points) do
          assert(point)
          if Drawing.near(point, mx,my, State.width) then
            return drawing_index,drawing,line_cache,i,point
          end
        end
      end
    end
  end
end
function Drawing.select_drawing_at_mouse(State)
  for drawing_index,drawing in ipairs(State.lines) do
    if drawing.mode == 'drawing' then
      local x, y = App.mouse_x(), App.mouse_y()
      local line_cache = State.line_cache[drawing_index]
      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
        return drawing
      end
    end
  end
end
function Drawing.contains_point(shape, p)
  if shape.mode == 'freehand' then
    -- not supported
  elseif shape.mode == 'line' or shape.mode == 'manhattan' then
    return shape.p1 == p or shape.p2 == p
  elseif shape.mode == 'polygon' or shape.mode == 'rectangle' or shape.mode == 'square' then
    return table.find(shape.vertices, p)
  elseif shape.mode == 'circle' then
    return shape.center == p
  elseif shape.mode == 'arc' then
    return shape.center == p
    -- ugh, how to support angles
  elseif shape.mode == 'deleted' then
    -- already done
  else
    print(shape.mode)
    assert(false)
  end
end
function Drawing.smoothen(shape)
  assert(shape.mode == 'freehand')
  for _=1,7 do
    for i=2,#shape.points-1 do
      local a = shape.points[i-1]
      local b = shape.points[i]
      local c = shape.points[i+1]
      b.x = round((a.x + b.x + c.x)/3)
      b.y = round((a.y + b.y + c.y)/3)
    end
  end
end
function round(num)
  return math.floor(num+.5)
end
function Drawing.find_or_insert_point(points, x,y, width)
  -- check if UI would snap the two points together
  for i,point in ipairs(points) do
    if Drawing.near(point, x,y, width) then
      return i
    end
  end
  table.insert(points, {x=x, y=y})
  return #points
end
function Drawing.near(point, x,y, width)
  local px,py = Drawing.pixels(x, width),Drawing.pixels(y, width)
  local cx,cy = Drawing.pixels(point.x, width), Drawing.pixels(point.y, width)
  return (cx-px)*(cx-px) + (cy-py)*(cy-py) < Same_point_distance*Same_point_distance
end
function Drawing.pixels(n, width)  -- parts to pixels
  return math.floor(n*width/256)
end
function Drawing.coord(n, width)  -- pixels to parts
  return math.floor(n*256/width)
end
function table.find(h, x)
  for k,v in pairs(h) do
    if v == x then
      return k
    end
  end
end