file load:
  cursor_line = 1
  first line is a drawing -> cursor_line = 2
click on text -> cursor moves
click on drawing -> cursor doesn't move
create drawing -> cursor bumps down below drawing
backspace
  cursor_pos == 0, previous line is a drawing -> delete drawing, cursor still visible at start of line
  cursor_pos == 0, previous line is text -> join lines, cursor still at same character