bugfix

manifestation: clicking past end of a long, wrapping line containing
non-ASCII would cause the cursor to disappear rather than position past
end of screen line. Hitting enter would then throw an assertion with the
following stack trace:

  Error: text.lua:381: bad argument #2 to 'sub' (number expected, got nil)
  stack traceback:
    [love "boot.lua"]:345: in function <[love "boot.lua"]:341>
    [C]: in function 'sub'
    text.lua:381: in function 'insert_return'
    text.lua:179: in function 'keychord_pressed'
    main.lua:495: in function 'keychord_pressed'
    keychord.lua:10: in function <keychord.lua:5>
    app.lua:34: in function <app.lua:25>
    [C]: in function 'xpcall'

cause: the click caused a call to Text.to_pos_on_line whose result was
not on a UTF-8 character boundary.

fix: make to_pos_on_line utf8-aware.

main.lua

@@ -86,6 +86,8 @@ Last_resize_time = nil
 -- blinking cursor
 Cursor_time = 0
 
+Quit = false
+
 end  -- App.initialize_globals
 
 function App.initialize(arg)
@@ -101,6 +103,7 @@ function App.initialize(arg)
   end
 
   initialize_font_settings(20)
+--?   Line_width = 80
 
   if #arg > 0 then
     Filename = arg[1]
@@ -122,6 +125,8 @@ function App.initialize(arg)
     jit.off()
     jit.flush()
   end
+
+  Quit = true
 end  -- App.initialize
 
 function initialize_window_geometry(geometry_spec)
@@ -258,6 +263,8 @@ function App.draw()
   if Search_term then
     Text.draw_search_bar()
   end
+
+--?   if Quit then os.exit(1) end
 end
 
 function App.update(dt)
@@ -319,6 +326,7 @@ function App.mousereleased(x,y, button)
       if line.mode == 'text' then
         if Text.in_line(line_index,line, x,y) then
           Cursor1 = {line=line_index, pos=Text.to_pos_on_line(line, x, y)}
+--?           print(Cursor1.line, Cursor1.pos)
           if Mousepress_shift then
             if Old_selection1.line == nil then
               Selection1 = Old_cursor1

text.lua

@@ -12,7 +12,7 @@ require 'text_tests'
 --  y coordinate drawn until in px
 --  position of start of final screen line drawn
 function Text.draw(line, line_width, line_index)
---?   print('text.draw')
+--?   print('text.draw', line_index)
   love.graphics.setColor(0,0,0)
   -- wrap long lines
   local x = 25
@@ -380,6 +380,9 @@ end
 
 function Text.insert_return()
   local byte_offset = utf8.offset(Lines[Cursor1.line].data, Cursor1.pos)
+--?   print(Cursor1.line, Cursor1.pos, #Lines[Cursor1.line].data)
+--?   print(Lines[Cursor1.line].data)
+  assert(byte_offset)
   table.insert(Lines, Cursor1.line+1, {mode='text', data=string.sub(Lines[Cursor1.line].data, byte_offset)})
   Lines[Cursor1.line].data = string.sub(Lines[Cursor1.line].data, 1, byte_offset-1)
   Lines[Cursor1.line].fragments = nil
@@ -678,6 +681,7 @@ end
 
 -- convert mx,my in pixels to schema-1 coordinates
 function Text.to_pos_on_line(line, mx, my)
+--?   print('Text.to_pos_on_line', mx, my, 'width', Line_width)
   if line.fragments == nil then
     Text.compute_fragments(line, Line_width)
   end
@@ -685,15 +689,20 @@ function Text.to_pos_on_line(line, mx, my)
   -- duplicate some logic from Text.draw
   local y = line.y
   for screen_line_index,screen_line_starting_pos in ipairs(line.screen_line_starting_pos) do
+--?     print('iter', y, screen_line_index, screen_line_starting_pos, string.sub(line.data, screen_line_starting_pos))
     local nexty = y + Line_height
     if my < nexty then
       -- On all wrapped screen lines but the final one, clicks past end of
       -- line position cursor on final character of screen line.
       -- (The final screen line positions past end of screen line as always.)
       if mx > Line_width and screen_line_index < #line.screen_line_starting_pos then
+--?         print('past end of non-final line; return')
         return line.screen_line_starting_pos[screen_line_index+1]
       end
-      local s = string.sub(line.data, screen_line_starting_pos)
+      local screen_line_starting_byte_offset = utf8.offset(line.data, screen_line_starting_pos)
+      assert(screen_line_starting_byte_offset)
+      local s = string.sub(line.data, screen_line_starting_byte_offset)
+--?       print('return', mx, Text.nearest_cursor_pos(s, mx), '=>', screen_line_starting_pos + Text.nearest_cursor_pos(s, mx) - 1)
       return screen_line_starting_pos + Text.nearest_cursor_pos(s, mx) - 1
     end
     y = nexty
@@ -872,13 +881,13 @@ function Text.populate_screen_line_starting_pos(line_index)
   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 = App.width(frag_text)
+--?     print(x, pos, frag, frag_width)
     if x + frag_width > Line_width then
       x = 25
---?       print(' ', #line.screen_line_starting_pos, line.data)
       table.insert(line.screen_line_starting_pos, pos)
+--?       print('new screen line:', #line.screen_line_starting_pos, pos)
     end
     x = x + frag_width
     local frag_len = utf8.len(frag)

text_tests.lua

@@ -127,6 +127,31 @@ function test_draw_wrapping_text_containing_non_ascii()
   App.screen.check(y, 'm ad', 'F - test_draw_wrapping_text_containing_non_ascii/screen:3')
 end
 
+function test_click_on_wrapping_line_containing_non_ascii()
+  io.write('\ntest_click_on_wrapping_line_containing_non_ascii')
+  -- display a wrapping line containing non-ASCII
+  App.screen.init{width=80, height=80}
+                  --  12345678901234
+  Lines = load_array{'madam I’m adam'}  -- notice the non-ASCII apostrophe
+  Line_width = 75
+  Cursor1 = {line=1, pos=1}
+  Screen_top1 = {line=1, pos=1}
+  Screen_bottom1 = {}
+  App.draw()
+  local y = Margin_top
+  App.screen.check(y, 'madam ', 'F - test_click_on_wrapping_line_containing_non_ascii/baseline/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'I’m ada', 'F - test_click_on_wrapping_line_containing_non_ascii/baseline/screen:2')
+  y = y + Line_height
+  App.screen.check(y, 'm', 'F - test_click_on_wrapping_line_containing_non_ascii/baseline/screen:3')
+  y = y + Line_height
+  -- click past the end of it
+  App.draw()
+  App.run_after_mouse_click(App.screen.width-2,y-2, '1')
+  -- cursor moves to end of line
+  check_eq(Cursor1.pos, 15, 'F - test_click_on_wrapping_line_containing_non_ascii/cursor')  -- one more than the number of UTF-8 code-points
+end
+
 function test_edit_wrapping_text()
   io.write('\ntest_edit_wrapping_text')
   App.screen.init{width=50, height=60}