one bug I've repeatedly run into while testing with Moby Dick

Dependencies

• [2] A2NV3WVO scrolling with up arrow
• [3] XOAHJ6M3 similar tests for cursor up
• [4] PYGMASTV disable some debug prints
• [5] IMEJA43L snapshot
• [6] C42QQZSF another piece of support for line wrapping in cursor up
• [7] 2RXZ3PGO beginning of a new approach to scroll+wrap
• [8] SVJZZDC3 snapshot - no, that's all wrong
• [*] BULPIBEG beginnings of a module for the text editor
• [*] YTSPVDZH first successful pagedown test, first bug found by test
• [*] PFT5Y2ZY move
• [*] MGT5FTJ3 first stab at supporting wrapping in cursor up
• [*] 3CSIZJ33 clearer comments
• [*] 3QNOKBFM beginnings of a test harness
• [*] AVTNUQYR basic test-enabled framework

Change contents

• replacement in text.lua at line 359
  [3.5311]→[2.486:552](∅→∅)
  − -- display lines starting from the second screen line of line 3
  [3.5311]

  [2.552]
  + -- display lines starting from second screen line of a line
• replacement in text.lua at line 374
  [2.906]→[3.6056:6122](∅→∅),[3.6056]→[3.6056:6122](∅→∅)
  − -- after hitting the up arrow the screen scrolls up by one line
  [2.906]

  [3.6122]
  + -- after hitting the up arrow the screen scrolls up to first screen line
• edit in text.lua at line 388
  [11.2153]

  [12.1]
  + function test_up_arrow_scrolls_up_to_final_screen_line()

  + print('test_up_arrow_scrolls_up_to_final_screen_line')

  + -- display lines starting just after a long line

  + App.screen.init{width=25+30, height=60}

  + Lines = load_array{'abc def', 'ghi', 'jkl', 'mno'}

  + Line_width = App.screen.width

  + Cursor1 = {line=2, pos=1}

  + Screen_top1 = {line=2, pos=1}

  + Screen_bottom1 = {}

  + Zoom = 1

  + local screen_top_margin = 15 -- pixels

  + local line_height = math.floor(15*Zoom) -- pixels

  + App.draw()

  + local y = screen_top_margin

  + App.screen.check(y, 'ghi', 'F - test_up_arrow_scrolls_up_to_final_screen_line/baseline/screen:1')

  + y = y + line_height

  + App.screen.check(y, 'jkl', 'F - test_up_arrow_scrolls_up_to_final_screen_line/baseline/screen:2')

  + y = y + line_height

  + App.screen.check(y, 'mno', 'F - test_up_arrow_scrolls_up_to_final_screen_line/baseline/screen:3')

  + -- after hitting the up arrow the screen scrolls up to final screen line of previous line

  + App.run_after_keychord('up')

  + y = screen_top_margin

  + App.screen.check(y, 'def', 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen:1')

  + y = y + line_height

  + App.screen.check(y, 'ghi', 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen:2')

  + y = y + line_height

  + App.screen.check(y, 'jkl', 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen:3')

  + check_eq(Screen_top1.line, 1, 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen_top')

  + check_eq(Screen_top1.pos, 5, 'F - test_up_arrow_scrolls_up_to_final_screen_line/screen_top')

  + check_eq(Cursor1.line, 1, 'F - test_up_arrow_scrolls_up_to_final_screen_line/cursor')

  + check_eq(Cursor1.pos, 5, 'F - test_up_arrow_scrolls_up_to_final_screen_line/cursor')

  + end

  +
• edit in text.lua at line 593
  [13.358]

  [3.3789]
  + --? print('found previous text line')
• edit in text.lua at line 595
  [3.3830]

  [3.3830]
  + Text.populate_screen_line_starting_pos(Cursor1.line)
• edit in text.lua at line 601
  [14.118]

  [3.3987]
  + --? print('has multiple screen lines')
• edit in text.lua at line 603
  [3.4075]

  [3.270]
  + --? print(#screen_line_starting_pos)
• replacement in text.lua at line 606
  [3.238]→[3.4076:4175](∅→∅)
  − if Screen_top1.line == Cursor1.line and Screen_top1.pos == screen_line_starting_pos then
  [3.238]

  [3.4175]
  + if Screen_top1.line > Cursor1.line then

  + Screen_top1.line = Cursor1.line
• edit in text.lua at line 923
  [3.8448]

  [10.1438]
  + function Text.populate_screen_line_starting_pos(line_index)

  + -- duplicate some logic from Text.draw

  + local line = Lines[line_index]

  + if line.fragments == nil then

  + Text.compute_fragments(line, Line_width)

  + end

  + local x = 25

  + local pos = 1

  + for _, f in ipairs(line.fragments) do

  + local frag, frag_text = f.data, f.text

  + --? print(x, frag)

  + -- render fragment

  + local frag_width = math.floor(App.width(frag_text)*Zoom)

  + if x + frag_width > Line_width then

  + x = 25

  + if line.screen_line_starting_pos == nil then

  + line.screen_line_starting_pos = {1, pos}

  + else

  + table.insert(line.screen_line_starting_pos, pos)

  + end

  + end

  + x = x + frag_width

  + local frag_len = utf8.len(frag)

  + pos = pos + frag_len

  + end

  + end

  +
• edit in app.lua at line 190
  [16.7197]

  [16.7197]
  + --? print('checking for "'..expected_contents..'" at y '..tostring(y))