[clutter] gdk: Use the Cogl visual on Xlib winsys

[Emmanuele Bassi <ebassi src gnome org>]

commit c91621e8c28bb190eaa9d59e08b180589a255cf3
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Wed Jun 10 11:55:50 2015 +0100

    gdk: Use the Cogl visual on Xlib winsys
    
    GDK 3.16 started selecting different visuals, to best comply with the
    requirements for OpenGL, and this has broken Clutter on GLX drivers that
    are fairly picky in how they select visuals and GLXFBConfig.
    
    GDK selects GLXFBConfig that do not include depth or stencil buffers;
    Cogl, on the other hand, needs both depth and stencil buffers, and keeps
    selecting the first available visual, assuming that the GLX driver will
    give us the best compliant one, as per specification. Sadly, some
    drivers will return incompatible configurations, and then bomb out when
    you try to embed Clutter inside GTK+, because of mismatched visuals.
    
    Cogl has an old, deprecated, Clutter-only API that allows us to retrieve
    the XVisualInfo mapping to the GLXFBConfig it uses; this means we should
    look up the GdkVisual for it when creating our own GdkWindows, instead
    of relying on the RGBA and system GdkVisuals exposed by GDK — at least
    on X11.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=747489

 clutter/gdk/clutter-stage-gdk.c |   50 ++++++++++++++++++++++++++++----------
 1 files changed, 37 insertions(+), 13 deletions(-)
---
diff --git a/clutter/gdk/clutter-stage-gdk.c b/clutter/gdk/clutter-stage-gdk.c
index 1c50208..8a301ae 100644
--- a/clutter/gdk/clutter-stage-gdk.c
+++ b/clutter/gdk/clutter-stage-gdk.c
@@ -29,6 +29,10 @@
 
 #include <cogl/cogl.h>
 
+#ifdef COGL_HAS_XLIB_SUPPORT
+#include <cogl/cogl-xlib.h>
+#endif
+
 #define GDK_DISABLE_DEPRECATION_WARNINGS
 
 #include <gdk/gdk.h>
@@ -183,7 +187,7 @@ clutter_stage_gdk_realize (ClutterStageWindow *stage_window)
   GdkWindowAttr attributes;
   gboolean cursor_visible;
   gboolean use_alpha;
-  gfloat   width, height;
+  gfloat width, height;
 
   if (backend->cogl_context == NULL)
     {
@@ -191,12 +195,7 @@ clutter_stage_gdk_realize (ClutterStageWindow *stage_window)
       return FALSE;
     }
 
-  if (stage_gdk->foreign_window)
-    {
-      width = gdk_window_get_width (stage_gdk->window);
-      height = gdk_window_get_height (stage_gdk->window);
-    }
-  else
+  if (!stage_gdk->foreign_window)
     {
       if (stage_gdk->window != NULL)
         {
@@ -239,13 +238,34 @@ clutter_stage_gdk_realize (ClutterStageWindow *stage_window)
               attributes.cursor = stage_gdk->blank_cursor;
             }
 
-          attributes.visual = NULL;
+          /* If the ClutterStage:use-alpha is set, but GDK does not have an
+           * RGBA visual, then we unset the property on the Stage
+           */
           if (use_alpha)
             {
-              attributes.visual = gdk_screen_get_rgba_visual (backend_gdk->screen);
+              if (gdk_screen_get_rgba_visual (backend_gdk->screen) == NULL)
+                {
+                  clutter_stage_set_use_alpha (stage_cogl->wrapper, FALSE);
+                  use_alpha = FALSE;
+                }
+            }
 
-              if (attributes.visual == NULL)
-                clutter_stage_set_use_alpha (stage_cogl->wrapper, FALSE);
+#if defined(GDK_WINDOWING_X11) && defined(COGL_HAS_XLIB_SUPPORT)
+          if (GDK_IS_X11_DISPLAY (backend_gdk->display))
+            {
+              XVisualInfo *xvisinfo = cogl_clutter_winsys_xlib_get_visual_info ();
+              if (xvisinfo != NULL)
+                {
+                  attributes.visual = gdk_x11_screen_lookup_visual (backend_gdk->screen,
+                                                                    xvisinfo->visualid);
+                }
+            }
+          else
+#endif
+            {
+              attributes.visual = use_alpha
+                                ? gdk_screen_get_rgba_visual (backend_gdk->screen)
+                                : gdk_screen_get_system_visual (backend_gdk->screen);
             }
 
           if (attributes.visual == NULL)
@@ -263,11 +283,15 @@ clutter_stage_gdk_realize (ClutterStageWindow *stage_window)
 
       clutter_stage_gdk_set_gdk_geometry (stage_gdk);
     }
+  else
+    {
+      width = gdk_window_get_width (stage_gdk->window);
+      height = gdk_window_get_height (stage_gdk->window);
+    }
 
   gdk_window_ensure_native (stage_gdk->window);
 
-  g_object_set_data (G_OBJECT (stage_gdk->window),
-                     "clutter-stage-window", stage_gdk);
+  g_object_set_data (G_OBJECT (stage_gdk->window), "clutter-stage-window", stage_gdk);
 
   stage_cogl->onscreen = cogl_onscreen_new (backend->cogl_context,
                                            width, height);