table.insert(column, initialize_pane_with_placeholder_coordinates('foo2'))

--?           love.graphics.setColor(0,0,1)
--?           love.graphics.line(pane.left, pane.top, pane.left + Display_settings.column_width, pane.top)
--?           love.graphics.line(pane.left, pane.top + Cache[pane.id].height - Padding_vertical*2, pane.left + Display_settings.column_width, pane.top + Cache[pane.id].height - Padding_vertical*2)

--? function App.update(dt)
--?   Cursor_time = Cursor_time + dt
--?   -- some hysteresis while resizing
--?   if Last_resize_time then
--?     if App.getTime() - Last_resize_time < 0.1 then
--?       return
--?     else
--?       Last_resize_time = nil
--?     end
--?   end
--?   if App.mouse_x() >= Editor_state.left-Margin_left and App.mouse_x() < Editor_state.right+Margin_right then
--?     love.mouse.setCursor(love.mouse.getSystemCursor('arrow'))
--?     edit.update(Editor_state, dt)
--?   else
--?     love.mouse.setCursor(love.mouse.getSystemCursor('hand'))
--?   end
--?   if Pan.x then
--?     Editor_state.left = Margin_left - math.max(Pan.x-App.mouse_x(), 0)
--?     Editor_state.right = 400 + Margin_right - math.max(Pan.x-App.mouse_x(), 0)
--?     Editor_state.width = Editor_state.right - Editor_state.left
--?     Editor_state.top = Margin_top - math.max(Pan.y-App.mouse_y(), 0)
--? --?     Display_settings.x = math.max(Pan.x-App.mouse_x(), 0)
--? --?     Display_settings.y = math.max(Pan.y-App.mouse_y(), 0)
--? --?     App.mouse_move(Pan.x-Display_settings.x, Pan.y-Display_settings.y)
--?   end
--? end
--? 

function App.update(dt)
  Cursor_time = Cursor_time + dt
  -- some hysteresis while resizing
  if Last_resize_time then
    if App.getTime() - Last_resize_time < 0.1 then
      return
    else
      Last_resize_time = nil
    end
  end
  if App.mouse_y() < Header_height then
    -- column header
    love.mouse.setCursor(love.mouse.getSystemCursor('arrow'))
  elseif in_pane(App.mouse_x(), App.mouse_y()) then
    love.mouse.setCursor(love.mouse.getSystemCursor('arrow'))
  else
    love.mouse.setCursor(love.mouse.getSystemCursor('hand'))
  end
  if Pan.x then
    Display_settings.x = math.max(Pan.x-App.mouse_x(), 0)
    Display_settings.y = math.max(Pan.y-App.mouse_y(), 0)
  end
end
function in_pane(x,y)
  local sx,sy = to_surface(x,y)
  local x = Gutter_width + Padding_horizontal
  for column_idx, column in ipairs(Surface) do
    if sx < x then
      return false
    end
    if sx < x + Margin_left + Display_settings.column_width + Margin_right then
      local y = Margin_top
      for pane_idx, pane in ipairs(column) do
        if sy < y then
          return false
        end
        if sy < y + Cache[pane.id].height - Padding_vertical*2 then
          return true
        end
        y = y + Cache[pane.id].height
      end
    end
    x = x + Margin_left + Display_settings.column_width + Margin_right + Padding_horizontal + Gutter_width + Padding_horizontal
  end
  return false
end
function to_surface(x, y)
  return x+Display_settings.x, y+Display_settings.y
end

--? end
--? 
--? function App.mousepressed(x,y, mouse_button)
--?   Cursor_time = 0  -- ensure cursor is visible immediately after it moves
--?   if x >= Editor_state.left - Margin_left and x < Editor_state.right + Margin_right then
--?     return edit.mouse_pressed(Editor_state, x,y, mouse_button)
--?   else
--?     Pan = {x=x, y=y}
--?   end
--? end
--? 
--? function App.mousereleased(x,y, mouse_button)
--?   Cursor_time = 0  -- ensure cursor is visible immediately after it moves
--?   if x >= Editor_state.left - Margin_left and x < Editor_state.right + Margin_right then
--?     return edit.mouse_released(Editor_state, x,y, mouse_button)
--?   else
--?     Pan = {}
--?   end

--? 

function App.mousepressed(x,y, mouse_button)
  Cursor_time = 0  -- ensure cursor is visible immediately after it moves
  Selection_first = {}
  Selection_second = {}
  Pan = {}
  if y < Margin_top then
    -- column headers currently not interactable
    return
  end
  local sx,sy = to_surface(x,y)
  if not in_pane(x,y) then
    Pan = {x=sx, y=sy}
    return
  end
end
function App.mousereleased(x,y, mouse_button)
  Cursor_time = 0  -- ensure cursor is visible immediately after it moves
  Pan = {}
end

      -- insert new drawing
      button('draw', {x=State.left - Margin_left + 4,y=y+4, w=12,h=12, color={1,1,0},
--?         icon = icon.insert_drawing,
        onpress1 = function()
                     Drawing.before = snapshot(State, line_index-1, line_index)
                     table.insert(State.lines, line_index, {mode='drawing', y=y, h=256/2, points={}, shapes={}, pending={}})
                     if State.cursor1.line >= line_index then
                       State.cursor1.line = State.cursor1.line+1
                     end
                     schedule_save(State)
                     record_undo_event(State, {before=Drawing.before, after=snapshot(State, line_index-1, line_index+1)})
                   end,
      })

      if State.show_cursor then
        button('draw', {x=State.left - Margin_left + 4,y=y+4, w=12,h=12, color={1,1,0},
--?           icon = icon.insert_drawing,  -- TODO
          onpress1 = function()
                       Drawing.before = snapshot(State, line_index-1, line_index)
                       table.insert(State.lines, line_index, {mode='drawing', y=y, h=256/2, points={}, shapes={}, pending={}})
                       if State.cursor1.line >= line_index then
                         State.cursor1.line = State.cursor1.line+1
                       end
                       schedule_save(State)
                       record_undo_event(State, {before=Drawing.before, after=snapshot(State, line_index-1, line_index+1)})
                     end,
        })
      end