[cogl] fix cogl_context_new crash if fail to connect renderer

[Robert Bragg <rbragg src gnome org>]

commit cc4c57888715a1e8910ccca10327bf97382f3254
Author: Robert Bragg <robert linux intel com>
Date:   Tue Apr 10 19:21:55 2012 +0100

    fix cogl_context_new crash if fail to connect renderer
    
    If a NULL display is passed to cogl_context_new() then it has to
    implicitly create a CoglRenderer and CoglDisplay and propagate any
    resulting errors back to the user. Previously the implementation relied
    on passing a NULL renderer to cogl_display_new() as the means for
    implicitly connecting to a renderer. The problem with this though is
    that cogl_display_new() isn't designed to ever return NULL but if it
    failed to connect to a renderer automatically it would do and then
    cogl_context_new would pass NULL to cogl_display_setup() leading to a
    crash.
    
    This patch changes the implementation of cogl_context_new() to now
    explicitly create a CoglRenderer and connect to it if a NULL display is
    given. This way we can easily propagate any errors. In addition
    cogl_display_new has been changed to abort if it fails to implicitly
    connect to a renderer due to a NULL renderer argument.
    
    An application needing to gracefully handle problems connecting to a
    renderer at runtime should manually instantiate and connect a renderer
    passing a GError argument to cogl_renderer_connect.
    
    Reviewed-by: Neil Roberts <neil linux intel com>

 cogl/cogl-context.c |   11 ++++++++++-
 cogl/cogl-display.c |    8 +-------
 2 files changed, 11 insertions(+), 8 deletions(-)
---
diff --git a/cogl/cogl-context.c b/cogl/cogl-context.c
index c15e2db..94ce2f1 100644
--- a/cogl/cogl-context.c
+++ b/cogl/cogl-context.c
@@ -188,7 +188,16 @@ cogl_context_new (CoglDisplay *display,
   memset (context->winsys_features, 0, sizeof (context->winsys_features));
 
   if (!display)
-    display = cogl_display_new (NULL, NULL);
+    {
+      CoglRenderer *renderer = cogl_renderer_new ();
+      if (!cogl_renderer_connect (renderer, error))
+        {
+          g_free (context);
+          return NULL;
+        }
+
+      display = cogl_display_new (renderer, NULL);
+    }
   else
     cogl_object_ref (display);
 
diff --git a/cogl/cogl-display.c b/cogl/cogl-display.c
index 4818bda..9ac1b68 100644
--- a/cogl/cogl-display.c
+++ b/cogl/cogl-display.c
@@ -91,13 +91,7 @@ cogl_display_new (CoglRenderer *renderer,
     display->renderer = cogl_renderer_new ();
 
   if (!cogl_renderer_connect (display->renderer, &error))
-    {
-      g_warning ("Failed to connect renderer: %s\n", error->message);
-      g_error_free (error);
-      g_object_unref (display->renderer);
-      g_slice_free (CoglDisplay, display);
-      return NULL;
-    }
+    g_error ("Failed to connect to renderer: %s\n", error->message);
 
   display->onscreen_template = onscreen_template;
   if (onscreen_template)