some temporary logging to catch a bug

The bug has been spotted twice:

1. In snap.love, I selected text in one node, then another, and hit:
  Error: text.lua:789: attempt to compare nil with number
  stack traceback:
    text.lua:789: in function 'lt1'
    select.lua:19: in function 'clip_selection'
    text.lua:32: in function 'draw'
    edit.lua:117: in function 'draw'
    [string "REPL"]:21: in function 'draw'
    main.lua:152: in function 'draw'
    app.lua:102: in function <app.lua:84>
    [C]: in function 'xpcall'
    app.lua:112: in function <app.lua:111>
    [C]: in function 'xpcall'

  Couldn't reproduce.

2. In text.love, inscript selected all text in a small buffer and then
   clicked outside the text. And got:

  Error: text.lua:784: attempt to compare nil with number
  Traceback
    [love "callbacks.lua"]:228: in function 'handler'
    text.lua:784: in function 'lt1'
    select.lua:19: in function 'clip_selection'
    text.lua:27: in function 'draw'
    edit.lua:117: in function 'draw'
    run.lua:136: in function 'draw'
    main.lua:148: in function 'draw'
    app.lua:42: in function <app.lua:22>
    [C]: in function 'xpcall'

  This is reproducible, and also across forks.

edit.lua

@@ -223,7 +223,7 @@ end
 
 function edit.mouse_press(State, x,y, mouse_button)
   if State.search_term then return end
---?   print('press', State.cursor1.line)
+  print_and_log(('edit.mouse_press: cursor at %d,%d').format(State.cursor1.line, State.cursor1.pos))
   if mouse_press_consumed_by_any_button_handler(State, x,y, mouse_button) then
     -- press on a button and it returned 'true' to short-circuit
     return
@@ -241,6 +241,7 @@ function edit.mouse_press(State, x,y, mouse_button)
         --  press and hold to start a selection: sets selection on press, cursor on release
         --  press and hold, then press shift: ignore shift
         --    i.e. mouse_release should never look at shift state
+        print_and_log(('edit.mouse_press: in line %d').format(line_index))
         State.old_cursor1 = State.cursor1
         State.old_selection1 = State.selection1
         State.mousepress_shift = App.shift_down()
@@ -248,7 +249,7 @@ function edit.mouse_press(State, x,y, mouse_button)
             line=line_index,
             pos=Text.to_pos_on_line(State, line_index, x, y),
         }
---?         print('selection', State.selection1.line, State.selection1.pos)
+        print_and_log(('edit.mouse_press: selection now %d,%d').format(State.selection1.line, State.selection1.pos))
         break
       end
     elseif line.mode == 'drawing' then
@@ -266,7 +267,7 @@ end
 
 function edit.mouse_release(State, x,y, mouse_button)
   if State.search_term then return end
---?   print('release', State.cursor1.line)
+  print_and_log(('edit.mouse_release: cursor at %d,%d').format(State.cursor1.line, State.cursor1.pos))
   if State.lines.current_drawing then
     Drawing.mouse_release(State, x,y, mouse_button)
     schedule_save(State)
@@ -275,15 +276,16 @@ function edit.mouse_release(State, x,y, mouse_button)
       Drawing.before = nil
     end
   else
+    print_and_log('edit.mouse_release: no current drawing')
     for line_index,line in ipairs(State.lines) do
       if line.mode == 'text' then
         if Text.in_line(State, line_index, x,y) then
---?           print('reset selection')
+          print_and_log(('edit.mouse_release: in line %d').format(line_index))
           State.cursor1 = {
               line=line_index,
               pos=Text.to_pos_on_line(State, line_index, x, y),
           }
---?           print('cursor', State.cursor1.line, State.cursor1.pos)
+          print_and_log(('edit.mouse_release: cursor now %d,%d').format(State.cursor1.line, State.cursor1.pos))
           if State.mousepress_shift then
             if State.old_selection1.line == nil then
               State.selection1 = State.old_cursor1
@@ -299,7 +301,7 @@ function edit.mouse_release(State, x,y, mouse_button)
         end
       end
     end
---?     print('selection:', State.selection1.line, State.selection1.pos)
+    print_and_log(('edit.mouse_release: finally selection %s,%s cursor %d,%d').format(tostring(State.selection1.line), tostring(State.selection1.pos), State.cursor1.line, State.cursor1.pos))
   end
 end
 

run.lua

@@ -48,6 +48,11 @@ function run.initialize(arg)
   end
 end
 
+function print_and_log(s)
+  print(s)
+  log(3, s)
+end
+
 function run.load_settings()
   love.graphics.setFont(love.graphics.newFont(Settings.font_height))
   -- determine default dimensions and flags

select.lua

@@ -8,13 +8,17 @@
 -- Result: positions spos,epos between apos,bpos.
 function Text.clip_selection(State, line_index, apos, bpos)
   if State.selection1.line == nil then return nil,nil end
+  print_and_log('text.clip_selection')
   -- min,max = sorted(State.selection1,State.cursor1)
   local minl,minp = State.selection1.line,State.selection1.pos
+  print_and_log(('text.clip_selection: one end from selection: %d,%d'):format(minl,minp))
   local maxl,maxp
   if App.mouse_down(1) then
     maxl,maxp = Text.mouse_pos(State)
+    print_and_log(('text.clip_selection: other end from mouse: %d,%d'):format(maxl,maxp))
   else
     maxl,maxp = State.cursor1.line,State.cursor1.pos
+    print_and_log(('text.clip_selection: other end from cursor: %d,%d'):format(maxl,maxp))
   end
   if Text.lt1({line=maxl, pos=maxp},
               {line=minl, pos=minp}) then