minor cleanup and a todo for later

Dependencies

• [2] IFTYOERM line.y -> line_cache.starty in a few more places
• [3] FUOURDEY clean up some final bifold code
• [4] VJ77YABH more efficient undo/redo
• [5] 73OCE2MC after much struggle, a brute-force undo
• [6] KKMFQDR4 editing source code from within the app
• [7] OI4FPFIN support drawings in the source editor
• [8] LF7BWEG4 group all editor globals
• [9] MTJEVRJR add state arg to a few functions

Change contents

• replacement in undo.lua at line 64
  [4.1624]→[4.1624:1687](∅→∅)
  − table.insert(event.lines, {mode='text', data=line.data})
  [4.1624]

  [4.1687]
  + table.insert(event.lines, {mode='text', data=line.data}) -- I've forgotten: should we deepcopy(line.data)?
• replacement in undo.lua at line 66
  [4.1726]→[4.1726:1978](∅→∅),[4.1978]→[2.1:239](∅→∅)
  − local points=deepcopy(line.points)

  − --? print('copying', line.points, 'with', #line.points, 'points into', points)

  − local shapes=deepcopy(line.shapes)

  − --? print('copying', line.shapes, 'with', #line.shapes, 'shapes into', shapes)

  − table.insert(event.lines, {mode='drawing', h=line.h, points=points, shapes=shapes, pending={}})

  − --? table.insert(event.lines, {mode='drawing', h=line.h, points=deepcopy(line.points), shapes=deepcopy(line.shapes), pending={}})
  [4.1726]

  [4.2236]
  + table.insert(event.lines, {mode='drawing', h=line.h, points=deepcopy(line.points), shapes=deepcopy(line.shapes), pending={}})
• replacement in source_undo.lua at line 64
  [4.1590]→[3.5:68](∅→∅)
  − table.insert(event.lines, {mode='text', data=line.data})
  [4.1590]

  [4.1671]
  + table.insert(event.lines, {mode='text', data=line.data}) -- I've forgotten: should we deepcopy(line.data)?
• replacement in source_undo.lua at line 66
  [4.1710]→[4.1710:2200](∅→∅)
  − local points=deepcopy(line.points)

  − --? print('copying', line.points, 'with', #line.points, 'points into', points)

  − local shapes=deepcopy(line.shapes)

  − --? print('copying', line.shapes, 'with', #line.shapes, 'shapes into', shapes)

  − table.insert(event.lines, {mode='drawing', h=line.h, points=points, shapes=shapes, pending={}})

  − --? table.insert(event.lines, {mode='drawing', h=line.h, points=deepcopy(line.points), shapes=deepcopy(line.shapes), pending={}})
  [4.1710]

  [4.2200]
  + table.insert(event.lines, {mode='drawing', h=line.h, points=deepcopy(line.points), shapes=deepcopy(line.shapes), pending={}})