end
  check_eq(Editor_state.cursor1.pos, 6, '1/cursor:pos')
  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_text_input(Editor_state, 'a')
  edit.run_after_keychord(Editor_state, 'up')
  -- cursor wraps
  check_eq(Editor_state.cursor1.line, 1, '1/cursor:line')
  Editor_state.lines = load_array{'abc ’abd'}  -- contains unicode quote
end
function test_search_wrap_upwards()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  check_eq(Editor_state.cursor1.pos, 2, '1/cursor:pos')
  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_text_input(Editor_state, 'a')
  edit.run_after_keychord(Editor_state, 'return')
  -- cursor wraps
  check_eq(Editor_state.cursor1.line, 1, '1/cursor:line')
  Editor_state.cursor1 = {line=2, pos=1}
  Text.redraw_all(Editor_state)
  Editor_state.lines = load_array{'’abc', 'def'}  -- contains unicode quote in first line
end
function test_search_wrap()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  check_eq(Editor_state.cursor1.pos, 2, '2/cursor:pos')
  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_text_input(Editor_state, 'a')
  -- search for previous occurrence
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.cursor1.line, 1, '2/cursor:line')
  Editor_state.cursor1 = {line=2, pos=1}
  Text.redraw_all(Editor_state)
  Editor_state.lines = load_array{'’abc', 'abd'}  -- contains unicode quote
end
function test_search_upwards()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  check_eq(Editor_state.cursor1.pos, 2, '2/cursor:pos')
  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_text_input(Editor_state, 'd')
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.cursor1.line, 2, '1/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, '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_text_input(Editor_state, 'de')
  edit.run_after_keychord(Editor_state, 'down')
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.cursor1.line, 4, '2/cursor:line')
  Editor_state.lines = load_array{'abc', 'def', 'ghi', '’deg'}  -- contains unicode quote in final line
end
function test_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, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 9, 'screen_top:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor')
  -- the screen is unchanged
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 4, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:3')
end
function test_pagedown_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', '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, 'baseline2/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'baseline2/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'ghij', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor')
  -- the screen is unchanged
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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 ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 1, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 5, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  -- empty first line
  y = y + Editor_state.line_height
  App.screen.check(y, 'abc', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 4, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'g', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'hi', 'screen:3')
end
function test_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', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 5, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'j', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:2')
end
function test_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_text_input(Editor_state, 'a')
  check_eq(Editor_state.screen_top1.line, 2, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  local y = Editor_state.top
  App.screen.check(y, 'a', 'screen:1')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'baseline/screen:3')
  -- after typing something the line wraps and the screen scrolls down
  edit.run_after_text_input(Editor_state, 'j')
  edit.run_after_text_input(Editor_state, 'k')
  edit.run_after_text_input(Editor_state, 'l')
  check_eq(Editor_state.screen_top1.line, 2, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 7, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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 ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 6, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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 ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 8, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_position_cursor_on_recently_edited_wrapping_line()
  -- draw a line wrapping over 2 screen lines
  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 ', 'baseline1/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl mno pqr ', 'baseline1/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'baseline1/screen:3')
  -- add to the line until it's wrapping over 3 screen lines
  edit.run_after_text_input(Editor_state, 's')
  edit.run_after_text_input(Editor_state, 't')
  edit.run_after_text_input(Editor_state, 'u')
  check_eq(Editor_state.cursor1.pos, 28, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc def ghi ', 'baseline2/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl mno pqr ', 'baseline2/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'stu', 'baseline2/screen:3')
  -- try to move the cursor earlier in the third screen line by clicking the mouse
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+Editor_state.line_height*2+5, 1)
  -- cursor should move
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 26, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'abcdef', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
end
function test_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', 'check')
end
-- 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()
  -- 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', 'data')
  -- cursor (remains) at start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data')
  -- cursor moves to start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data:1')
  check_eq(Editor_state.lines[2].data, 'mno', 'data:2')
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data:1')
  check_eq(Editor_state.lines[2].data, 'def', 'data:2')
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data:1')
  check_eq(Editor_state.lines[2].data, 'f', 'data:2')
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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_text_input(Editor_state, 'g')
  check_eq(Editor_state.cursor1.line, 2, 'baseline/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'baseline/cursor:pos')
  check_nil(Editor_state.selection1.line, 'baseline/selection:line')
  check_nil(Editor_state.selection1.pos, 'baseline/selection:pos')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'defg', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'baseline/screen:3')
  -- undo
  edit.run_after_keychord(Editor_state, 'C-z')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection:line')
  check_nil(Editor_state.selection1.pos, 'selection:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'screen:3')
end
function test_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, 'baseline/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'baseline/cursor:pos')
  check_nil(Editor_state.selection1.line, 'baseline/selection:line')
  check_nil(Editor_state.selection1.pos, 'baseline/selection:pos')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', '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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection:line')
  check_nil(Editor_state.selection1.pos, 'selection:pos')
--?   check_eq(Editor_state.selection1.line, 2, 'selection:line')
--?   check_eq(Editor_state.selection1.pos, 4, 'selection:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'defg', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'screen:3')
end
function test_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_text_input(Editor_state, 'x')
  check_eq(Editor_state.lines[1].data, 'xbc', 'baseline')
  check_nil(Editor_state.selection1.line, '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, 'line')
  check_eq(Editor_state.selection1.pos, 2, 'pos')
end
function test_search()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  App.screen.check(y, 'mn', 'screen:3')

  App.screen.check(y, 'mn', 'screen:3')
end
function test_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, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 9, 'screen_top:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor')
  -- the screen is unchanged
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 4, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:3')
end
function test_pagedown_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', '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, 'baseline2/screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'baseline2/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'ghij', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor')
  -- the screen is unchanged
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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 ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 1, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 5, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  -- empty first line
  y = y + Editor_state.line_height
  App.screen.check(y, 'abc', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:3')
end
function test_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', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 4, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'g', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'hi', 'screen:3')
end
function test_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', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 5, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'j', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:2')
end
function test_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_text_input(Editor_state, 'a')
  check_eq(Editor_state.screen_top1.line, 2, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  local y = Editor_state.top
  App.screen.check(y, 'a', 'screen:1')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'baseline/screen:3')
  -- after typing something the line wraps and the screen scrolls down
  edit.run_after_text_input(Editor_state, 'j')
  edit.run_after_text_input(Editor_state, 'k')
  edit.run_after_text_input(Editor_state, 'l')
  check_eq(Editor_state.screen_top1.line, 2, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 7, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghij', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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 ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 6, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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 ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 8, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'def', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi ', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_position_cursor_on_recently_edited_wrapping_line()
  -- draw a line wrapping over 2 screen lines
  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 ', 'baseline1/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl mno pqr ', 'baseline1/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'baseline1/screen:3')
  -- add to the line until it's wrapping over 3 screen lines
  edit.run_after_text_input(Editor_state, 's')
  edit.run_after_text_input(Editor_state, 't')
  edit.run_after_text_input(Editor_state, 'u')
  check_eq(Editor_state.cursor1.pos, 28, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc def ghi ', 'baseline2/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl mno pqr ', 'baseline2/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'stu', 'baseline2/screen:3')
  -- try to move the cursor earlier in the third screen line by clicking the mouse
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+Editor_state.line_height*2+5, 1)
  -- cursor should move
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 26, 'cursor:pos')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  y = Editor_state.top
  App.screen.check(y, 'abcdef', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ghi', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'jkl', 'screen:3')
end
function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', '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', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'kl', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'mno', 'screen:3')
  check_eq(Editor_state.screen_top1.line, 3, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
  check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
end
function test_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', 'check')
end
-- 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()
  -- 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', 'data')
  -- cursor (remains) at start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data')
  -- cursor moves to start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data:1')
  check_eq(Editor_state.lines[2].data, 'mno', 'data:2')
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data:1')
  check_eq(Editor_state.lines[2].data, 'def', 'data:2')
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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', 'data:1')
  check_eq(Editor_state.lines[2].data, 'f', 'data:2')
  -- cursor remains at start of selection
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  -- selection is cleared
  check_nil(Editor_state.selection1.line, 'selection')
end
function test_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_text_input(Editor_state, 'g')
  check_eq(Editor_state.cursor1.line, 2, 'baseline/cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'baseline/cursor:pos')
  check_nil(Editor_state.selection1.line, 'baseline/selection:line')
  check_nil(Editor_state.selection1.pos, 'baseline/selection:pos')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'defg', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'baseline/screen:3')
  -- undo
  edit.run_after_keychord(Editor_state, 'C-z')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection:line')
  check_nil(Editor_state.selection1.pos, 'selection:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'screen:3')
end
function test_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, 'baseline/cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'baseline/cursor:pos')
  check_nil(Editor_state.selection1.line, 'baseline/selection:line')
  check_nil(Editor_state.selection1.pos, 'baseline/selection:pos')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', '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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 5, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection:line')
  check_nil(Editor_state.selection1.pos, 'selection:pos')
--?   check_eq(Editor_state.selection1.line, 2, 'selection:line')
--?   check_eq(Editor_state.selection1.pos, 4, 'selection:pos')
  y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'defg', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'xyz', 'screen:3')
end
function test_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_text_input(Editor_state, 'x')
  check_eq(Editor_state.lines[1].data, 'xbc', 'baseline')
  check_nil(Editor_state.selection1.line, '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, 'line')
  check_eq(Editor_state.selection1.pos, 2, 'pos')
end
function test_search()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'ghi', '’deg'}  -- contains unicode quote in final line
  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_text_input(Editor_state, 'd')
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.cursor1.line, 2, '1/cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, '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_text_input(Editor_state, 'de')
  edit.run_after_keychord(Editor_state, 'down')
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.cursor1.line, 4, '2/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, '2/cursor:pos')
end
function test_search_upwards()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'’abc', 'abd'}  -- contains unicode quote
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, 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_text_input(Editor_state, 'a')
  -- search for previous occurrence
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.cursor1.line, 1, '2/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, '2/cursor:pos')
end
function test_search_wrap()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'’abc', 'def'}  -- contains unicode quote in first line
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=2, 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_text_input(Editor_state, 'a')
  edit.run_after_keychord(Editor_state, 'return')
  -- cursor wraps
  check_eq(Editor_state.cursor1.line, 1, '1/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, '1/cursor:pos')
end
function test_search_wrap_upwards()
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc ’abd'}  -- contains unicode quote
  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_text_input(Editor_state, 'a')
  edit.run_after_keychord(Editor_state, 'up')
  -- cursor wraps
  check_eq(Editor_state.cursor1.line, 1, '1/cursor:line')
  check_eq(Editor_state.cursor1.pos, 6, '1/cursor:pos')
end

--?   print_and_log(('edit.mouse_release(%d,%d): cursor at %d,%d'):format(x,y, State.cursor1.line, State.cursor1.pos))