From 8247bdf4f9b940fe69165ae6556511fcc9ca3a5d Mon Sep 17 00:00:00 2001
From: Neil Roberts <neil@linux.intel.com>
Date: Tue, 12 Jan 2010 21:44:40 +0000
Subject: [PATCH] cogl-framebuffer: Return gboolean from try_creating_fbo
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When try_creating_fbo fails it returns 0 to report the error and if it
succeeds it returns ‘flags’. However cogl_offscreen_new_to_texture
also passes in 0 for the flags as the last fallback to create the fbo
with nothing but the color buffer. In that case it will return 0
regardless of whether it succeeded so the last fallback will always be
considered a failure.

To fix this it now just returns a gboolean to indicate whether it
succeeded and the flags used for each attempt is assigned when passing
the argument rather than from the return value of the function.

Also if the only configuration that succeeded was with flags==0 then
it would always try all combinations because last_working_flags would
also be zero. To avoid this it now uses a separate gboolean to mark
whether we found a successful set of flags.

http://bugzilla.openedhand.com/show_bug.cgi?id=1873
---
 clutter/cogl/cogl/cogl-framebuffer.c | 56 ++++++++++++++--------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/clutter/cogl/cogl/cogl-framebuffer.c b/clutter/cogl/cogl/cogl-framebuffer.c
index 64f586385..8124186d0 100644
--- a/clutter/cogl/cogl/cogl-framebuffer.c
+++ b/clutter/cogl/cogl/cogl-framebuffer.c
@@ -247,7 +247,7 @@ _cogl_framebuffer_get_projection_stack (CoglHandle handle)
   return framebuffer->projection_stack;
 }
 
-static TryFBOFlags
+static gboolean
 try_creating_fbo (CoglOffscreen *offscreen,
                   TryFBOFlags flags,
                   CoglHandle texture)
@@ -263,14 +263,14 @@ try_creating_fbo (CoglOffscreen *offscreen,
   _COGL_GET_CONTEXT (ctx, FALSE);
 
   if (!cogl_texture_get_gl_texture (texture, &tex_gl_handle, &tex_gl_target))
-    return 0;
+    return FALSE;
 
   if (tex_gl_target != GL_TEXTURE_2D
 #ifdef HAVE_COGL_GL
       && tex_gl_target != GL_TEXTURE_RECTANGLE_ARB
 #endif
       )
-    return 0;
+    return FALSE;
 
   /* We are about to generate and bind a new fbo, so when next flushing the
    * journal, we will need to rebind the current framebuffer... */
@@ -352,18 +352,18 @@ try_creating_fbo (CoglOffscreen *offscreen,
           GLuint renderbuffer = GPOINTER_TO_UINT (l->data);
           GE (glDeleteRenderbuffers (1, &renderbuffer));
         }
-      return 0;
+      return FALSE;
     }
 
-  return flags;
+  return TRUE;
 }
 
 CoglHandle
 cogl_offscreen_new_to_texture (CoglHandle texhandle)
 {
   CoglOffscreen      *offscreen;
-  TryFBOFlags         flags;
-  static TryFBOFlags  last_working_flags = 0;
+  static TryFBOFlags  flags;
+  static gboolean     have_working_flags = FALSE;
 
   _COGL_GET_CONTEXT (ctx, COGL_INVALID_HANDLE);
 
@@ -393,33 +393,33 @@ cogl_offscreen_new_to_texture (CoglHandle texhandle)
   offscreen = g_new0 (CoglOffscreen, 1);
   offscreen->texture = cogl_handle_ref (texhandle);
 
-  if (!(last_working_flags &&
-        (flags = try_creating_fbo (offscreen, last_working_flags,
-                                   texhandle))) &&
-      !(flags = try_creating_fbo (offscreen, _TRY_DEPTH_STENCIL,
-                                  texhandle)) &&
-      !(flags = try_creating_fbo (offscreen, _TRY_DEPTH | _TRY_STENCIL,
-                                  texhandle)) &&
-      !(flags = try_creating_fbo (offscreen, _TRY_STENCIL, texhandle)) &&
-      !(flags = try_creating_fbo (offscreen, _TRY_DEPTH, texhandle)) &&
-      !(flags = try_creating_fbo (offscreen, 0, texhandle)))
+  if ((have_working_flags &&
+       try_creating_fbo (offscreen, flags, texhandle)) ||
+      try_creating_fbo (offscreen, flags = _TRY_DEPTH_STENCIL, texhandle) ||
+      try_creating_fbo (offscreen, flags = _TRY_DEPTH | _TRY_STENCIL,
+                        texhandle) ||
+      try_creating_fbo (offscreen, flags = _TRY_STENCIL, texhandle) ||
+      try_creating_fbo (offscreen, flags = _TRY_DEPTH, texhandle) ||
+      try_creating_fbo (offscreen, flags = 0, texhandle))
+    {
+      /* Record that the last set of flags succeeded so that we can
+         try that set first next time */
+      have_working_flags = TRUE;
+
+      _cogl_framebuffer_init (COGL_FRAMEBUFFER (offscreen),
+                              COGL_FRAMEBUFFER_TYPE_OFFSCREEN,
+                              cogl_texture_get_width (texhandle),
+                              cogl_texture_get_height (texhandle));
+
+      return _cogl_offscreen_handle_new (offscreen);
+    }
+  else
     {
       g_free (offscreen);
-      last_working_flags = 0;
       /* XXX: This API should probably have been defined to take a GError */
       g_warning ("%s: Failed to create an OpenGL framebuffer", G_STRLOC);
       return COGL_INVALID_HANDLE;
     }
-  /* Save the final set of flags that worked so we can hopefully construct
-   * subsequent buffers faster. */
-  last_working_flags = flags;
-
-  _cogl_framebuffer_init (COGL_FRAMEBUFFER (offscreen),
-                          COGL_FRAMEBUFFER_TYPE_OFFSCREEN,
-                          cogl_texture_get_width (texhandle),
-                          cogl_texture_get_height (texhandle));
-
-  return _cogl_offscreen_handle_new (offscreen);
 }
 
 static void