ui/gtk: use GtkGlArea on wayland only

For dma-buf support we need a egl context.  The gtk x11 backend uses glx
contexts though.  We can't use the GtkGlArea widget on x11 because of
that, so use our own gtk-egl code instead.  wayland continues to use
the GtkGlArea widget.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20180306090951.22932-5-kraxel@redhat.com

ui/gtk.c

@@ -2440,12 +2440,15 @@ static void early_gtk_display_init(DisplayOptions *opts)
     assert(opts->type == DISPLAY_TYPE_GTK);
     if (opts->has_gl && opts->gl) {
 #if defined(CONFIG_OPENGL)
-#if defined(CONFIG_GTK_GL)
-        gtk_use_gl_area = true;
-        gtk_gl_area_init();
-#else
-        gtk_egl_init();
+#if defined(CONFIG_GTK_GL) && defined(GDK_WINDOWING_WAYLAND)
+        if (GDK_IS_WAYLAND_DISPLAY(gdk_display_get_default())) {
+            gtk_use_gl_area = true;
+            gtk_gl_area_init();
+        }
 #endif
+        {
+            gtk_egl_init();
+        }
 #endif
     }