[Mesa-dev] [PATCH] mesa: Loosen glBlitFramebuffer restrictions on depthstencil buffers (v2)

Chad Versace chad.versace at linux.intel.com
Wed Jan 18 12:31:59 PST 2012

--- snip

Supporting Z32 -> Z32_FLOAT is a bad idea. So I've amended the patch
to avoid that.

--- end snip

This loosens the format validation in glBlitFramebuffer. When blitting
depth bits, don't require an exact match between the depth formats; only
require that the two formats have the same number of depth bits and the
same depth datatype (float vs uint). Ditto for stencil.

Between S8_Z24 buffers, the EXT_framebuffer_blit spec allows
glBlitFramebuffer to blit the depth and stencil bits separately. So I see
no reason to prevent blitting the depth bits between X8_Z24 and S8_Z24 or
the stencil bits between S8 and S8_Z24. However, we of course don't want
to allow blitting from Z32 to Z32_FLOAT.


Fixes Piglit fbo/fbo-blit-d24s8 on Intel drivers with separate stencil

The problem was that, on Intel drivers with separate stencil, the default
framebuffer has separate depth and stencil buffers with formats X8_Z24 and
S8. The test attempts to blit the depth bits from a S8_Z24 buffer into the
default framebuffer.

v2: Check that depth datatypes match in order prevent Z32 -> Z32_FLOAT.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44665
Note: This is a candidate for the 8.0 branch.
CC: Brian Paul <brianp at vmware.com>
CC: Kenneth Graunke <kenneth at whitecape.org>
CC: Iam Romanick <idr at freedesktop.org>
Reported-by: Xunx Fang <xunx.fang at intel.com>
Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
 src/mesa/main/fbobject.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/mesa/main/fbobject.c b/src/mesa/main/fbobject.c
index 0524959..2b3ac2e 100644
--- a/src/mesa/main/fbobject.c
+++ b/src/mesa/main/fbobject.c
@@ -2709,9 +2709,13 @@ _mesa_BlitFramebufferEXT(GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
       if ((readRb == NULL) || (drawRb == NULL)) {
-      else if (readRb->Format != drawRb->Format) {
+      else if (_mesa_get_format_bits(readRb->Format, GL_STENCIL_BITS) !=
+	       _mesa_get_format_bits(drawRb->Format, GL_STENCIL_BITS)) {
+	 /* There is no need to check the stencil datatype here, because
+	  * there is only one: GL_UNSIGNED_INT.
+	  */
          _mesa_error(ctx, GL_INVALID_OPERATION,
-                     "glBlitFramebufferEXT(stencil buffer format mismatch)");
+                     "glBlitFramebufferEXT(stencil buffer size mismatch)");
@@ -2731,7 +2735,10 @@ _mesa_BlitFramebufferEXT(GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
       if ((readRb == NULL) || (drawRb == NULL)) {
 	 mask &= ~GL_DEPTH_BUFFER_BIT;
-      else if (readRb->Format != drawRb->Format) {
+      else if ((_mesa_get_format_bits(readRb->Format, GL_DEPTH_BITS) !=
+	        _mesa_get_format_bits(drawRb->Format, GL_DEPTH_BITS)) ||
+	       (_mesa_get_format_datatype(readRb->Format) !=
+		_mesa_get_format_datatype(drawRb->Format))) {
          _mesa_error(ctx, GL_INVALID_OPERATION,
                      "glBlitFramebufferEXT(depth buffer format mismatch)");

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