Don't event-buffer ConfigureNotify, MapNotify, and ReparentNotify events

When event buffering is enabled for a qube, previously Qt applications
would exhibit some strange flickering / element resizing when opening
application menus. This appears to be because ConfigureNotify events
were being delayed, causing Qt to draw elements of the user interface
with incorrect size and position information. It would then likely have
to redraw the menu with the correct information once that information
was available to it.

ConfigureNotify, MapNotify, and ReparentNotify events all look like they
can be passed through without negative effects on anonymity, so make
them exempt from event buffering. This appears to resolve the flickering
issue.

Fixes: QubesOS/qubes-issues#10286

Author: ArrayBolt3

gui-daemon/xside.c

@@ -2815,7 +2815,16 @@ static void process_xevent(Ghandles * g)
     XEvent event_buffer;
     XNextEvent(g->display, &event_buffer);
     if (g->ebuf_max_delay > 0) {
-        ebuf_queue_xevent(g, event_buffer);
+        switch (event_buffer.type) {
+        case ConfigureNotify:
+        case ReparentNotify:
+        case MapNotify:
+            process_xevent_core(g, event_buffer);
+            break;
+        default:
+            ebuf_queue_xevent(g, event_buffer);
+            break;
+        }
     } else {
         process_xevent_core(g, event_buffer);
     }