message: Optimize pygame_viewer performance of drawing with alpha
diff: @@ -221,7 +221,12 @@ class PygameViewer(BaseViewer):
  pg.event.get() # call necessary for visbility of pygame viewer on macos
  def clear(self):
  - self.alpha_surf = dict()
  + # Clear each surface, could occupy lot of memory if using many
  + # different alpha values
  + if self.alpha_surf:
  + for s in self.alpha_surf.values():
  + s.fill(self.background_color)
  +
  self.screen.fill(self.background_color)
  self.screen_surface.fill(self.background_color)
  