I like to adjust or disable a feature of gtk3 (or gnome-shell?) because it causes a delay or at least need to remove the delay when bringing a window in/out of focus. My multi window application suffers from this delay:
I see is that all widgets like buttons, entries, etc. are set to in-sensitive/gray look at time the window they are contained is loosing focus and they return to normal when the window focus returns. I tried to turn off animations, but that does not disable this behavior.
My old program version based on gtk2 based does not have this feature (same gnome shell). So I conclude gtk3 is some how managing this.
I so far was not able to find out how to disable this.