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

[Christoph Bumiller]

On 19.01.2012 19:53, Ian Romanick wrote:
> On 01/18/2012 12:31 PM, Chad Versace wrote:
>> --- 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.
>>

So is it also allowed to blit from S8Z24 to Z24S8 ? Could we also allow
to blit from RGBA8 to BGRA8 then, please ?

That would fix my multisampling fail - all applications that use
framebuffer_multisample try to blit resolve directly from an MS
renderbuffer to the window system back buffer and that means I have to
know somehow which ordering the window system chooses, which is rather
inconvenient and made me hack-disable RGBA8 in the gallium driver, i.e.
lie about what formats it supports.

If I recall correctly, the NV blob does allow resolving between BGRA and
RGBA.

>> --------
>>
>> Fixes Piglit fbo/fbo-blit-d24s8 on Intel drivers with separate stencil
>> enabled.
>>
>> 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>
>
> Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
>
>> 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)) {
>>        mask&= ~GL_STENCIL_BUFFER_BIT;
>>         }
>> -      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)");
>>            return;
>>         }
>>      }
>> @@ -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)");
>>            return;
>
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