stop putting button state in a global

Symptom: a test (test_click_to_create_drawing) started randomly failing
after I inserted a `return` 2 commits ago.

Cause: my tests call edit.draw, but button handlers only get cleared in
app.draw. So my tests weren't clearing button handlers, and every call
to edit.draw was accumulating states. Still unclear why those were going
to different state objects after the `return`, but anyway. I'm not going
to understand every last thing that happens when things go wrong, just
guarantee they can't go wrong. And the way to do that is to decentralize
button handlers to each state that receives them.

The State object in buttons.lua doesn't have to be Editor_state. It just
has to be some table that provides a Schelling Point for shared state.

1 files changed, 3 insertions, 2 deletions

diff --git a/edit.lua b/edit.lua
index 5bc8bad..3c92d49 100644
--- a/edit.lua
+++ b/edit.lua
@@ -128,6 +128,7 @@ function edit.fixup_cursor(State)
 end
 
 function edit.draw(State)
+  State.button_handlers = {}
   App.color(Text_color)
   assert(#State.lines == #State.line_cache)
   if not Text.le1(State.screen_top1, State.cursor1) then
@@ -151,7 +152,7 @@ function edit.draw(State)
       end
       if line.data == '' then
         -- button to insert new drawing
-        button('draw', {x=4,y=y+4, w=12,h=12, color={1,1,0},
+        button(State, 'draw', {x=4,y=y+4, w=12,h=12, color={1,1,0},
           icon = icon.insert_drawing,
           onpress1 = function()
                        Drawing.before = snapshot(State, line_index-1, line_index)
@@ -208,7 +209,7 @@ end
 function edit.mouse_pressed(State, x,y, mouse_button)
   if State.search_term then return end
 --?   print('press', State.selection1.line, State.selection1.pos)
-  if propagate_to_button_handlers(x,y, mouse_button) then
+  if propagate_to_button_handlers(State, x,y, mouse_button) then
     -- press on a button and it returned 'true' to short-circuit
     return
   end