[gtk/gtk-3-22] x11: Set a transparent background on windows by default

[Benjamin Otte <otte src gnome org>]

commit 2ce63a86ba689aa41eb47409c889c469497478b0
Author: Benjamin Otte <otte redhat com>
Date:   Fri May 4 11:26:15 2018 +0200

    x11: Set a transparent background on windows by default
    
    This avoids black flicker on compositing WMs when a window is first shown.

 gdk/x11/gdkwindow-x11.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index 70daed9b6d..e484b58253 100644
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -1147,6 +1147,9 @@ _gdk_x11_display_create_window_impl (GdkDisplay    *display,
   if (attributes_mask & GDK_WA_TYPE_HINT)
     gdk_window_set_type_hint (window, attributes->type_hint);
 
+  if (!window->input_only)
+    gdk_window_x11_set_background (window, NULL);
+
   gdk_x11_event_source_select_events ((GdkEventSource *) display_x11->event_source,
                                       GDK_WINDOW_XID (window), event_mask,
                                       StructureNotifyMask | PropertyChangeMask);