bugfix: pagedown was sometimes bouncing up

Dependencies

• [2] ILOA5BYF separate data structure for each line's cache data
• [3] LERERVPH keep one screen line of overlap on pagedown
• [4] CVGE3SIG I feel confident now that page-down is working.
• [5] GK47BBCY start passing left/right margins everywhere
• [6] 3ZSUBI57 drop some redundant args from Text.draw
• [7] MXA3RZYK deduce left/right from state where possible
• [8] HGC5RGJP switch to line index in a function
• [9] MYC7XR5Q bugfix: lines that aren't drawn from the start
• [10] H2DPLWMV snapshot: wrapping long lines at word boundaries
• [*] LXTTOB33 extract a couple of files
• [*] BULPIBEG beginnings of a module for the text editor

Change contents

• edit in text_tests.lua at line 1087
  [12.10095]

  [12.10095]
  + function test_pagedown_never_moves_up()

  + io.write('\ntest_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, 'F - test_pagedown_never_moves_up/screen_top:line')

  + check_eq(Editor_state.screen_top1.pos, 9, 'F - test_pagedown_never_moves_up/screen_top:pos')

  + end

  +
• replacement in text.lua at line 20
  [3.1818]→[3.104:141](∅→∅)
  − local screen_line_starting_pos = 1
  [3.1818]

  [2.3821]
  + local screen_line_starting_pos = State.screen_top1.pos