App doesn't handle mouse event until button loses focus

[CoNsTaRs]

Description

with_callback doesn't handle On::MouseUp and On::MouseDown until the button loses focus.

Version / OS

• azul version:
  5984b80

• Operating system:
  Linux (Ubuntu 18.04)

• Windowing system (X11 or Wayland, Linux only):
  Wayland

Steps to Reproduce

Hello World example, label doesn't actually update when mouse up and down, it updates only on next mouse down or when button loses focus.

[jhwgh1968]

FWIW, I encountered this on master along with other rendering glitches.

I tried to bisect this, going all the way back to f2d7625 (committed in May of this year). That version and a couple before it seemed to react better to the mouse, but due to other rendering glitches, the counter never updated at all or did not display.

In other words, I have no idea where this actually broke, and it seems really hard to pin down due to other issues. But I will open separate bugs for those once I can characterize them better.