keep all text cache writes inside text.lua

Dependencies

• [2] WJBZZQE4 fold together two largely similar cases
• [3] BULPIBEG beginnings of a module for the text editor
• [4] 2POFQQLW keep cursor on screen when pressing 'down'
• [5] H2DPLWMV snapshot: wrapping long lines at word boundaries
• [6] 537TQ2QN some more logging
• [7] LF7BWEG4 group all editor globals
• [8] JY4VK7L2 rename
• [9] 3TFEAQSW start using some globals
• [10] 73OCE2MC after much struggle, a brute-force undo
• [11] CVGE3SIG I feel confident now that page-down is working.
• [12] 4VKEE43Z bugfix
• [13] LXTTOB33 extract a couple of files
• [14] 2L5MEZV3 experiment: new edit namespace
• [15] GK47BBCY start passing left/right margins everywhere
• [16] LNUHQOGH start passing in Editor_state explicitly
• [17] X3F7ECSL add state arg to some functions
• [18] MXA3RZYK deduce left/right from state where possible
• [19] 3ZSUBI57 drop some redundant args from Text.draw
• [20] M6TH7VSZ rip out notion of Line_width

Change contents

• replacement in text.lua at line 9
  [3.1568]→[3.1:103](∅→∅),[3.103]→[3.3:41](∅→∅)
  − -- return values:

  − -- y coordinate drawn until in px

  − -- position of start of final screen line drawn

  − function Text.draw(State, line_index)
  [3.1568]

  [3.1129]
  + -- draw a line starting from startpos to screen at y between State.left and State.right

  + -- return the final y, and position of start of final screen line drawn

  + function Text.draw(State, line_index, y, startpos)
• edit in text.lua at line 15
  [3.81]

  [3.1747]
  + line.starty = y

  + line.startpos = startpos
• edit in text.lua at line 19
  [3.76]→[3.82:106](∅→∅)
  − local y = line.starty
• replacement in edit.lua at line 133
  [2.91]→[3.4396:4442](∅→∅),[3.4396]→[3.4396:4442](∅→∅)
  − line.starty = y

  − line.startpos = 1
  [2.91]

  [2.92]
  + local startpos = 1
• replacement in edit.lua at line 135
  [2.143]→[2.143:189](∅→∅)
  − line.startpos = State.screen_top1.pos
  [2.143]

  [2.189]
  + startpos = State.screen_top1.pos
• replacement in edit.lua at line 152
  [3.5239]→[2.973:1038](∅→∅)
  − y, State.screen_bottom1.pos = Text.draw(State, line_index)
  [3.5239]

  [3.3585]
  + y, State.screen_bottom1.pos = Text.draw(State, line_index, y, startpos)