[gnome-settings-daemon/wip/carlosg/xwayland-startup-side-channel: 4/6] common: Replace DISPLAY with setup-only side channel display

[Carlos Garnacho <carlosg src gnome org>]

commit 2600d5bcb7b5b8f1afce5602ab9245afb0e96555
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Nov 15 11:30:14 2019 +0100

    common: Replace DISPLAY with setup-only side channel display
    
    If it exists and is available, this display should be used to let g-s-d
    x11 services (i.e. gsd-xsettings) set up the X11 server before a Xwayland
    client proceeds.

 plugins/common/daemon-skeleton-gtk.h | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/plugins/common/daemon-skeleton-gtk.h b/plugins/common/daemon-skeleton-gtk.h
index 87bafb3d..f39fd5d6 100644
--- a/plugins/common/daemon-skeleton-gtk.h
+++ b/plugins/common/daemon-skeleton-gtk.h
@@ -222,6 +222,12 @@ main (int argc, char **argv)
         set_empty_gtk_theme (TRUE);
 
 #ifdef GDK_BACKEND
+       {
+               const gchar *setup_display = getenv ("GNOME_SETUP_DISPLAY");
+               if (setup_display)
+                       g_setenv ("DISPLAY", setup_display, TRUE);
+       }
+
         gdk_set_allowed_backends (GDK_BACKEND);
 #endif