[Cogl] [PATCH] tweak: Support retrieving depth textures from framebuffers

[Robert Bragg]

From: Robert Bragg <robert at linux.intel.com>

Ok I went with renaming the enable_ function to
set_depth_texture_enabled. Although I'm quite tempted by the idea of
using other verbs than 'set' and 'get' for some reason I was feeling
conservative since we have no precedent for that in Cogl currently.

That said it really is quite verbose now so maybe it would be worth
introducing _enable and _disable verbs.

This patch should hopefully address the points you raised, and
should be folded back into Damien's original patch.

kind regards,
- Robert

-- >8 --

Renames cogl_framebuffer_enable_depth_texture to
cogl_framebuffer_set_depth_texture_enabled, adds a corresponding
_get_depth_texture function, actually references the enabled argument
in _set_depth_texture_enabled, no longer assert that the api is only
used with offscreen framebuffers but rather report a suitable error
during allocation and frees any allocated depth_texture in
_cogl_offscreen_free().
---
 cogl/cogl-framebuffer.c |   28 ++++++++++++++++++++++------
 cogl/cogl-framebuffer.h |   23 +++++++++++++++++++----
 2 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/cogl/cogl-framebuffer.c b/cogl/cogl-framebuffer.c
index 984b3b8..4dd93cd 100644
--- a/cogl/cogl-framebuffer.c
+++ b/cogl/cogl-framebuffer.c
@@ -817,6 +817,9 @@ _cogl_offscreen_free (CoglOffscreen *offscreen)
   if (offscreen->texture != NULL)
     cogl_object_unref (offscreen->texture);
 
+  if (offscreen->depth_texture != NULL)
+    cogl_object_unref (offscreen->depth_texture);
+
   g_free (offscreen);
 }
 
@@ -1291,6 +1294,15 @@ cogl_framebuffer_allocate (CoglFramebuffer *framebuffer,
 
   if (framebuffer->type == COGL_FRAMEBUFFER_TYPE_ONSCREEN)
     {
+      if (framebuffer->config.depth_texture_enabled)
+        {
+          g_set_error (error, COGL_FRAMEBUFFER_ERROR,
+                       COGL_FRAMEBUFFER_ERROR_ALLOCATE,
+                       "Can't allocate onscreen framebuffer with a "
+                       "texture based depth buffer");
+          return FALSE;
+        }
+
       if (!winsys->onscreen_init (onscreen, error))
         return FALSE;
     }
@@ -2032,24 +2044,28 @@ cogl_framebuffer_get_color_format (CoglFramebuffer *framebuffer)
 }
 
 void
-cogl_framebuffer_enable_depth_texture (CoglFramebuffer *framebuffer,
-                                       CoglBool         enabled)
+cogl_framebuffer_set_depth_texture_enabled (CoglFramebuffer *framebuffer,
+                                            CoglBool enabled)
 {
   _COGL_RETURN_IF_FAIL (!framebuffer->allocated);
-  _COGL_RETURN_IF_FAIL (cogl_is_offscreen (framebuffer));
 
-  framebuffer->config.depth_texture_enabled = TRUE;
+  framebuffer->config.depth_texture_enabled = enabled;
+}
+
+CoglBool
+cogl_framebuffer_get_depth_texture_enabled (CoglFramebuffer *framebuffer)
+{
+  return framebuffer->config.depth_texture_enabled;
 }
 
 CoglTexture *
 cogl_framebuffer_get_depth_texture (CoglFramebuffer *framebuffer)
 {
-  _COGL_RETURN_VAL_IF_FAIL (cogl_is_offscreen (framebuffer), NULL);
-
   /* lazily allocate the framebuffer... */
   if (!cogl_framebuffer_allocate (framebuffer, NULL))
     return NULL;
 
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_offscreen (framebuffer), NULL);
   return COGL_OFFSCREEN(framebuffer)->depth_texture;
 }
 
diff --git a/cogl/cogl-framebuffer.h b/cogl/cogl-framebuffer.h
index 6b303eb..1046190 100644
--- a/cogl/cogl-framebuffer.h
+++ b/cogl/cogl-framebuffer.h
@@ -800,7 +800,7 @@ CoglPixelFormat
 cogl_framebuffer_get_color_format (CoglFramebuffer *framebuffer);
 
 /**
- * cogl_framebuffer_enable_depth_texture:
+ * cogl_framebuffer_set_depth_texture_enabled:
  * @framebuffer: A #CoglFramebuffer
  * @enabled: TRUE or FALSE
  *
@@ -809,7 +809,7 @@ cogl_framebuffer_get_color_format (CoglFramebuffer *framebuffer);
  * cogl_framebuffer_get_depth_texture().
  *
  * <note>It's possible that your GPU does not support depth textures. You
- * should check the COGL_FEATURE_ID_DEPTH_TEXTURE feature before using this
+ * should check the %COGL_FEATURE_ID_DEPTH_TEXTURE feature before using this
  * function.</note>
  * <note>It's not valid to call this function after the framebuffer has been
  * allocated as the creation of the depth texture is done at allocation time.
@@ -818,8 +818,23 @@ cogl_framebuffer_get_color_format (CoglFramebuffer *framebuffer);
  * Since: 2.0
  */
 void
-cogl_framebuffer_enable_depth_texture (CoglFramebuffer *framebuffer,
-                                       gboolean         enabled);
+cogl_framebuffer_set_depth_texture_enabled (CoglFramebuffer *framebuffer,
+                                            CoglBool enabled);
+
+/**
+ * cogl_framebuffer_get_depth_texture_enabled:
+ * @framebuffer: A #CoglFramebuffer
+ *
+ * Queries whether texture based depth buffer has been enabled via
+ * cogl_framebuffer_set_depth_texture_enabled().
+ *
+ * Return value: %TRUE if a depth texture has been enabled, else
+ *               %FALSE.
+ *
+ * Since: 2.0
+ */
+CoglBool
+cogl_framebuffer_get_depth_texture_enabled (CoglFramebuffer *framebuffer);
 
 /**
  * cogl_framebuffer_get_depth_texture:
-- 
1.7.7.6