This is a copy of a similar comment in another place, which explains why WS_EX_TRANSPARENT windows get a special treatment.
https://bugzilla.gnome.org/show_bug.cgi?id=758484
3701a60 GDK W32: Add a comment for clarity
gdk/win32/gdkwindow-win32.c | 3 +++
1 file changed, 3 insertions(+)
Upstream: git.gnome.org