graphics: fix needs_redraw + properly handle videoexpose event to update canvas. Closes #28

(now drawing happen only when needed. carefully check for any bugs !!!)

kivy/core/window/window_pygame.py

@@ -222,8 +222,11 @@ class WindowPygame(WindowBase):
                 Clock.unschedule(cb)
                 Clock.schedule_once(cb, .1)
 
+            elif event.type == pygame.VIDEOEXPOSE:
+                self.canvas.ask_update()
+
             # ignored event
-            elif event.type in (pygame.ACTIVEEVENT, pygame.VIDEOEXPOSE):
+            elif event.type == pygame.ACTIVEEVENT:
                 pass
 
             # unhandled event !

kivy/graphics/instructions.pyx

@@ -68,7 +68,7 @@ cdef class Instruction:
 
     property needs_redraw:
         def __get__(self):
-            return bool(self.flags | GI_NEEDS_UPDATE)
+            return bool(self.flags & GI_NEEDS_UPDATE)
 
 
 cdef class InstructionGroup(Instruction):