Created attachment 199761 [details]
Testcases

I noticed that when the focused widget or the state of a widget change, other widgets receive many redraw signals.
Consider for instance the attached test application, consisting of a window with a GtkBox, a GtkToolbar and a GtkCanvas. Default focus is on a GtkToolButton. There are Gtk2 and Gtk3 variants, test_gtk2.py and test_gtk3.py.

Observations, using test_gtk3.py:
- A button-press on the window border (which causes the focused ToolButton to unfocus) causes the drawingarea to redraw three times.
- Setting window.set_focus(None) stops the drawingarea from getting redrawn in the above described situation.
- A mouse-leave on a non-focused GtkToolButton causes the drawingarea to redraw 4 times.
- In general, each focus change and each state change causes 4 redraws for any widget which is a parent of the focus-changed/state-changed widget.

Observations, using test_gtk2.py
- The drawingarea never gets redrawn on toolbutton focus / state changes
- In general, each focus change and each state change causes just 1 redraw for any widget which is a parent of the focus-changed/state-changed widget.

Using gtk3-3.2.1-1.fc16.x86_64