gdk: Add gdk_window_set_pass_through

An pass_through window is something you can draw in but does not
affect event handling. Normally if a window has with no event mask set
for a particular event then input events in it go to its parent window
(X11 semantics), whereas if pass_through is enabled the window below
the window will get the event. The later mode is useful when the
window is partially transparent. Note that an pass-through windows can
have child windows that are not pass-through so they can still get events
on some parts.

Semantically, this behaves the same as an regular window with
gdk_window_set_child_input_shapes() called on it (and re-called any
time a child is changed), but its far more efficient and easy to use.

This allows us to fix the testoverlay input stacking test.

https://bugzilla.gnome.org/show_bug.cgi?id=750568

https://bugs.freedesktop.org/show_bug.cgi?id=90917

1 files changed, 1 insertions, 0 deletions

diff --git a/gdk/gdkinternals.h b/gdk/gdkinternals.h
index d1d1e4d167..e5ec4b204d 100644
--- a/gdk/gdkinternals.h
+++ b/gdk/gdkinternals.h
@@ -314,6 +314,7 @@ struct _GdkWindow
   guint8 fullscreen_mode;
 
   guint input_only : 1;
+  guint pass_through : 1;
   guint modal_hint : 1;
   guint composited : 1;
   guint has_alpha_background : 1;