With update debugging enabled, calls to
gdk_window_invalidate_region() clear the invalidated region of the
screen to a noticeable color, and GDK pauses for a short time
before sending exposes to windows during
gdk_window_process_updates(). The net effect is that you can see
the invalid region for each window and watch redraws as they
occur. This allows you to diagnose inefficiencies in your application.
In essence, because the GDK rendering model prevents all flicker, if you are redrawing the same region 400 times you may never notice, aside from noticing a speed problem. Enabling update debugging causes GTK to flicker slowly and noticeably, so you can see exactly what’s being redrawn when, in what order.
The —gtk-debug=updates command line option passed to GTK+ programs
enables this debug option at application startup time. That’s
usually more useful than calling
yourself, though you might want to use this function to enable
updates sometime after application startup time.
Deprecated since: 3.22
Please do not use it in newly written code.