[gnome-shell/wip/wayland: 2/4] Don't try to use GLX if Cogl isn't using that Winsys

[Neil Roberts <nroberts src gnome org>]

commit acdba78681014ee6085c1a79a368e794fa4f7efc
Author: Neil Roberts <neil linux intel com>
Date:   Thu Mar 15 15:58:36 2012 +0000

    Don't try to use GLX if Cogl isn't using that Winsys
    
    Instead of directly using symbols from GLX to check for the swap event
    notification, the plugin now first verifies that the Cogl renderer is
    actually using the GLX winsys and then indirectly fetches the pointers
    for the GLX functions using cogl_get_proc_address. That way it will
    continue to work if Cogl is using an EGL winsys.

 src/gnome-shell-plugin.c |   56 ++++++++++++++++++++++++++++++++++++----------
 1 files changed, 44 insertions(+), 12 deletions(-)
---
diff --git a/src/gnome-shell-plugin.c b/src/gnome-shell-plugin.c
index da46bbd..9b4be1c 100644
--- a/src/gnome-shell-plugin.c
+++ b/src/gnome-shell-plugin.c
@@ -28,6 +28,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+#define CLUTTER_ENABLE_EXPERIMENTAL_API
+#define COGL_ENABLE_EXPERIMENTAL_API
 #include <clutter/clutter.h>
 #include <clutter/x11/clutter-x11.h>
 #include <GL/glx.h>
@@ -99,6 +101,7 @@ struct _GnomeShellPlugin
   int glx_error_base;
   int glx_event_base;
   guint have_swap_event : 1;
+  CoglContext *cogl_context;
 
   ShellGlobal *global;
 };
@@ -142,30 +145,59 @@ gnome_shell_plugin_init (GnomeShellPlugin *shell_plugin)
 {
 }
 
-static void
-gnome_shell_plugin_start (MetaPlugin *plugin)
+static gboolean
+gnome_shell_plugin_has_swap_event (GnomeShellPlugin *shell_plugin)
 {
-  GnomeShellPlugin *shell_plugin = GNOME_SHELL_PLUGIN (plugin);
+  MetaPlugin *plugin = META_PLUGIN (shell_plugin);
+  CoglDisplay *cogl_display =
+    cogl_context_get_display (shell_plugin->cogl_context);
+  CoglRenderer *renderer = cogl_display_get_renderer (cogl_display);
+  const char * (* query_extensions_string) (Display *dpy, int screen);
+  Bool (* query_extension) (Display *dpy, int *error, int *event);
   MetaScreen *screen;
   MetaDisplay *display;
   Display *xdisplay;
-  GError *error = NULL;
-  int status;
   const char *glx_extensions;
-  GjsContext *gjs_context;
+
+  /* We will only get swap events if Cogl is using GLX */
+  if (cogl_renderer_get_winsys_id (renderer) != COGL_WINSYS_ID_GLX)
+    return FALSE;
 
   screen = meta_plugin_get_screen (plugin);
   display = meta_screen_get_display (screen);
 
   xdisplay = meta_display_get_xdisplay (display);
 
-  glXQueryExtension (xdisplay,
-                     &shell_plugin->glx_error_base,
-                     &shell_plugin->glx_event_base);
+  query_extensions_string =
+    (void *) cogl_get_proc_address ("glXQueryExtensionsString");
+  query_extension =
+    (void *) cogl_get_proc_address ("glXQueryExtension");
+
+  query_extension (xdisplay,
+                   &shell_plugin->glx_error_base,
+                   &shell_plugin->glx_event_base);
+
+  glx_extensions =
+    query_extensions_string (xdisplay,
+                             meta_screen_get_screen_number (screen));
+
+  return strstr (glx_extensions, "GLX_INTEL_swap_event") != NULL;
+}
+
+static void
+gnome_shell_plugin_start (MetaPlugin *plugin)
+{
+  GnomeShellPlugin *shell_plugin = GNOME_SHELL_PLUGIN (plugin);
+  GError *error = NULL;
+  int status;
+  GjsContext *gjs_context;
+  ClutterBackend *backend;
+
+  backend = clutter_get_default_backend ();
+  shell_plugin->cogl_context = clutter_backend_get_cogl_context (backend);
 
-  glx_extensions = glXQueryExtensionsString (xdisplay,
-                                             meta_screen_get_screen_number (screen));
-  shell_plugin->have_swap_event = strstr (glx_extensions, "GLX_INTEL_swap_event") != NULL;
+  shell_plugin->have_swap_event =
+    gnome_shell_plugin_has_swap_event (shell_plugin);
 
   shell_perf_log_define_event (shell_perf_log_get_default (),
                                "glx.swapComplete",