[Mesa-dev] [PATCH 2/3] mesa: Skip clearing color buffers when color writes are disabled.

[Kenneth Graunke]

On 03/24/2014 08:07 AM, Brian Paul wrote:
> On 03/24/2014 02:52 AM, Kenneth Graunke wrote:
>> WebGL Aquarium in Chrome 24 actually hits this.
>>
>> v2: Move to core Mesa (wisely suggested by Ian); only consider
>>      components which actually exist.
>>
>> v3: Use _mesa_format_has_color_component to determine whether components
>>      actually exist, fixing alpha format handling.
>>
>> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
>> ---
>>   src/mesa/main/clear.c | 20 +++++++++++++++++++-
>>   1 file changed, 19 insertions(+), 1 deletion(-)
>>
>> Thanks for the review!  You're absolutely right about ALPHA formats.
>>
>> I think this version should actually work :)
>>
>> diff --git a/src/mesa/main/clear.c b/src/mesa/main/clear.c
>> index 077c5fc..e2566c0 100644
>> --- a/src/mesa/main/clear.c
>> +++ b/src/mesa/main/clear.c
>> @@ -106,6 +106,24 @@ _mesa_ClearColorIuiEXT(GLuint r, GLuint g, GLuint
>> b, GLuint a)
>>   }
>>
>>
>> +static bool
>> +color_buffer_writes_enabled(const struct gl_context *ctx, unsigned idx)
>> +{
>> +   struct gl_renderbuffer *rb = ctx->DrawBuffer->_ColorDrawBuffers[idx];
>> +   GLuint c;
>> +   GLubyte colorMask = 0;
>> +
>> +   if (rb) {
>> +      for (c = 0; c < 4; c++) {
>> +         if (_mesa_format_has_color_component(rb->Format, c))
>> +            colorMask |= ctx->Color.ColorMask[idx][c];
>> +      }
>> +   }
>> +
>> +   return colorMask != 0;
>> +}
>> +
>> +
>>   /**
>>    * Clear buffers.
>>    *
>> @@ -181,7 +199,7 @@ _mesa_Clear( GLbitfield mask )
>>            for (i = 0; i < ctx->DrawBuffer->_NumColorDrawBuffers; i++) {
>>               GLint buf = ctx->DrawBuffer->_ColorDrawBufferIndexes[i];
>>
>> -            if (buf >= 0) {
>> +            if (buf >= 0 && color_buffer_writes_enabled(ctx, i)) {
>>                  bufferMask |= 1 << buf;
>>               }
>>            }
>>
> 
> I still think a comment on the new function would be nice.  Looks good
> though.
> 
> Reviewed-by: Brian Paul <brianp at vmware.com>

Oops, sorry...I missed your request for a comment.  Added in v4 (with no
actual code changes), and pushed.  Thanks!

--Ken


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