-- major tests for text editing flows

function test_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, '#lines')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  check_eq(Editor_state.screen_top1.line, 1, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
end

function test_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, '#lines')
  check_eq(Editor_state.cursor1.line, 2, 'cursor')
end

function test_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, '#lines')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
end

function test_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, '#lines')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
  check_eq(Editor_state.screen_top1.line, 1, 'screen_top')
end

function test_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_text_input(Editor_state, 'a')
  local y = Editor_state.top
  App.screen.check(y, 'a', 'screen:1')
end

function test_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()
  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, 'check')
end

function test_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, 'check')
end

function test_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, 'line')
  check_eq(Editor_state.cursor1.pos, 4, 'pos')  -- past end of line
end

function test_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, 'line')
  check_eq(Editor_state.cursor1.pos, 1, 'pos')
end

function test_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, 'check')
end

function test_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, 'check')
end

function test_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, 'check')
end

function test_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, 'check')
end

function test_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, 'check')
end

function test_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, 'line')
  check_eq(Editor_state.cursor1.pos, 5, 'pos')
end

function test_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, 'check')
end

function test_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, 'check')
end

function test_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, 'check')
end

function test_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, 'check')
end

function test_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, 'line')
  check_eq(Editor_state.cursor1.pos, 4, 'pos')
end

function test_click_moves_cursor()
  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
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  -- selection is empty to avoid perturbing future edits
  check_nil(Editor_state.selection1.line, 'selection:line')
  check_nil(Editor_state.selection1.pos, 'selection:pos')
end

function test_click_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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection is empty to avoid perturbing future edits')
end

function test_click_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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection is empty to avoid perturbing future edits')
end

function test_click_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, 'cursor')
end

function test_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', '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_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', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'de', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'fgh', 'screen:3')
end

function test_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 ', '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_click_on_wrapping_line()
  -- display two screen 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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection is empty to avoid perturbing future edits')
end

function test_click_on_wrapping_line_takes_margins_into_account()
  -- display two screen 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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection is empty to avoid perturbing future edits')
end

function test_draw_text_wrapping_within_word()
  -- arrange a screen line that needs to be split within a 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 ', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'e fgh', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'ijk', 'screen:3')
end

function test_draw_wrapping_text_containing_non_ascii()
  -- draw a long line 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', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'am I', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, '’m a', 'screen:3')
end

function test_click_past_end_of_screen_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 ', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, "I'm ad", '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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 12, 'cursor:pos')
end

function test_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", '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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 12, 'cursor:pos')
end

function test_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 ', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, "I'm ad", 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'am', '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, 'cursor')  -- one more than the number of UTF-8 code-points
end

function test_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 ', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'I’m ad', 'baseline/screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'am', '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, 'cursor')  -- one more than the number of UTF-8 code-points
end

function test_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 ', '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, 'cursor')
end

function test_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_release(Editor_state, 'lshift')
  -- selection persists even after shift is released
  check_eq(Editor_state.selection1.line, 1, 'selection:line')
  check_eq(Editor_state.selection1.pos, 1, 'selection:pos')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
end

function test_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, 'check')
  check_eq(Editor_state.lines[1].data, 'abc', 'data')
end

function test_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_text_input(Editor_state, 'x')
  -- selected text is deleted and replaced with the key
  check_eq(Editor_state.lines[1].data, 'xbc', 'check')
end

function test_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_press(Editor_state, 'd', 'd')
  edit.text_input(Editor_state, 'D')
  edit.key_release(Editor_state, 'd')
  App.fake_key_release('lshift')
  -- selected text is deleted and replaced with the key
  check_nil(Editor_state.selection1.line, 'check')
  check_eq(Editor_state.lines[1].data, 'Dbc', 'data')
end

function test_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', 'clipboard')
  -- selection is reset since shift key is not pressed
  check(Editor_state.selection1.line, 'check')
end

function test_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', 'clipboard')
  -- selected text is deleted
  check_eq(Editor_state.lines[1].data, 'bc', 'data')
end

function test_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', 'check')
end

function test_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', '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')
  -- 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, 'check')
  check_eq(Editor_state.lines[1].data, 'ahi', 'data')
end

function test_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_text_input(Editor_state, 'g')
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'de', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'fg', 'screen:3')
end

function test_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', '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')
  -- hitting the enter key splits the line
  edit.run_after_keychord(Editor_state, 'return')
  check_eq(Editor_state.screen_top1.line, 1, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'a', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'bc', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:3')
end

function test_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, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  check_eq(Editor_state.lines[1].data, '', 'data:1')
  check_eq(Editor_state.lines[2].data, 'abc', 'data:2')
end

function test_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', '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')
  -- 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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  y = Editor_state.top
  App.screen.check(y, 'axy', 'screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'zbc', 'screen:2')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', 'screen:3')
end

function test_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, 'selection:line')
  check_eq(Editor_state.selection1.pos, 2, 'selection:pos')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
end

function test_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, 'selection:line')
  check_eq(Editor_state.selection1.pos, 2, 'selection:pos')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 4, 'cursor:pos')
end

function test_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, 'selection:line')
  check_eq(Editor_state.selection1.pos, 2, 'selection:pos')
  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
end

function test_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, 'check')
end

function test_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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'def', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 2, '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')
end

function test_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', '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', '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, 'screen_top')
  check_eq(Editor_state.cursor1.line, 3, 'cursor')
  y = Editor_state.top + drawing_height
  App.screen.check(y, 'def', 'screen:1')
end

function test_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 ', '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 pagedown we scroll down the very long wrapping line
  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')
  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, '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_skips_drawing()
  -- some lines of text with a drawing intermixed
  local drawing_width = 50
  App.screen.init{width=Editor_state.left+drawing_width, height=100}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc',               -- height 15
                                  '```lines', '```',   -- height 25
                                  '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', 'baseline/screen:1')
  y = y + Editor_state.line_height
  local drawing_height = Drawing_padding_height + drawing_width/2  -- default
  y = y + drawing_height
  App.screen.check(y, 'ghi', 'baseline/screen:3')
  check(Editor_state.cursor_x, 'baseline/cursor_x')
  -- after hitting the down arrow the cursor moves down by 2 lines, skipping the drawing
  edit.run_after_keychord(Editor_state, 'down')
  check_eq(Editor_state.cursor1.line, 3, 'cursor')
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_skips_drawing()
  -- some lines of text with a drawing intermixed
  local drawing_width = 50
  App.screen.init{width=Editor_state.left+drawing_width, height=100}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc',               -- height 15
                                  '```lines', '```',   -- height 25
                                  'ghi'}
  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
  local drawing_height = Drawing_padding_height + drawing_width/2  -- default
  y = y + drawing_height
  App.screen.check(y, 'ghi', 'baseline/screen:3')
  check(Editor_state.cursor_x, 'baseline/cursor_x')
  -- after hitting the up arrow the cursor moves up by 2 lines, skipping the drawing
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
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_line_skipping_drawing()
  -- display lines 3/4/5 with a drawing just off screen at line 2
  App.screen.init{width=120, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', '```lines', '```', 'def', 'ghi', 'jkl'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=1}
  Editor_state.screen_top1 = {line=3, 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 to previous text 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')
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 staan><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   ./bootstrap run apps/hex <span class="ni">&amp;lt;</span> apps/boot.hex <span class="ni">&amp;gt;</span> boot.bin<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L14&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 14 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   dd if=boot.bin of=disk.img conv=notrunc<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L15&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 15 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># To run:<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L16&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 16 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   qemu-system-i386 disk.img<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L17&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 17 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># Or:<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L18&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 18 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   bochs -f apps/boot.bochsrc  # boot.bochsrc loads disk.img<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L19&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 19 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L20&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 20 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># Since we start out in 16-bit mode, we need instructions SubX doesn&#39;t<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L21&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 21 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># support.<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L22&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 22 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># This file contains just hex bytes and comments. Zero error-checking. Make<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L23&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 23 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># liberal use of:<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L24&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 24 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   - comments documenting expected offsets<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L25&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 25 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   - size checks on the emitted file (currently: 512 bytes)<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L26&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 26 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   - xxd to eyeball that offsets contain expected bytes<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L27&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 27 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L28&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 28 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>## 16-bit entry point<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L29&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 29 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L30&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 30 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># Upon reset, the IBM PC<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L31&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 31 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   loads the first sector (512 bytes)<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L32&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 32 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   from some bootable image (see the boot sector marker at the end of this file)<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L33&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 33 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span>#   to the address range [0x7c00, 0x7e00)<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L34&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 34 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L35&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 35 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># offset 00 (address 0x7c00):<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L36&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 36 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># disable interrupts for this initialization<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L37&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 37 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  fa  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># cli<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L38&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 38 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L39&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 39 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># initialize segment registers<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L40&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 40 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># this isn&#39;t always needed, but is considered safe not to assume<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L41&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 41 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  b8 00 00  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># ax <span class="ni">&amp;lt;</span>- 0<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L42&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 42 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  8e d8  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># ds <span class="ni">&amp;lt;</span>- ax<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L43&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 43 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  8e d0  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># ss <span class="ni">&amp;lt;</span>- ax<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L44&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 44 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  8e c0  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># es <span class="ni">&amp;lt;</span>- ax<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L45&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 45 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  8e e0  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># fs <span class="ni">&amp;lt;</span>- ax<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L46&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 46 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  8e e8  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># gs <span class="ni">&amp;lt;</span>- ax<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L47&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 47 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L48&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 48 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># We don&#39;t read or write the stack before we get to 32-bit mode. No function<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L49&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 49 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># calls, so we don&#39;t need to initialize the stack.<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L50&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 50 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L51&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 51 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># 0e:<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L52&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 52 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># load more sectors from disk<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L53&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 53 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  b4 02  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># ah <span class="ni">&amp;lt;</span>- 2  # read sectors from disk<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L54&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 54 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># dl comes conveniently initialized at boot time with the index of the device being booted<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L55&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 55 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  b5 00  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># ch <span class="ni">&amp;lt;</span>- 0  # cylinder 0<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L56&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 56 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  b6 00  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># dh <span class="ni">&amp;lt;</span>- 0  # track 0<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L57&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 57 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  b1 02  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># cl <span class="ni">&amp;lt;</span>- 2  # second sector, 1-based<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L58&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 58 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  b0 01  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># al <span class="ni">&amp;lt;</span>- 1  # number of sectors to read<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L59&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 59 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># address to write sectors to = es:bx = 0x7e00, contiguous with boot segment<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L60&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 60 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  bb 00 00  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># bx <span class="ni">&amp;lt;</span>- 0<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L61&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 61 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  8e c3  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># es <span class="ni">&amp;lt;</span>- bx<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L62&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 62 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  bb 00 7e  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;Comment&quot;</span><span class="p">&gt;</span># bx <span class="ni">&amp;lt;</span>- 0x7e00<span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>
<span class="p">&lt;</span><span class="nt">span</span> <span class="na">id</span><span class="o">=</span><span class="s">&quot;L63&quot;</span> <span class="na">class</span><span class="o">=</span><span class="s">&quot;LineNr&quot;</span><span class="p">&gt;</span> 63 <span class="p">&lt;/</span><span class="nt">span</span><span class="p">&gt;</span>  cd 13  <span class="p">&lt;</span><span class="nt">span</span> <span class="na">class</span><sp