Re: [Mesa3d-dev] OSMesa16 UseSoftwareAlphaBuffers init problem

[Brian P. <br...@va...>]

"J.P. Delport" wrote:
> 
> Hello,
> 
> I tried some polygon anti-aliasing with OSMesa16 (RGBA buffer like
> osdemo16) and all seemed OK with
> glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA), but with
> glBlendFunc(GL_SRC_ALPHA_SATURATE,GL_ONE) the blending went berzerk. I
> found that mesa was reading back the wrong frame buffer alpha values
> with _mesa_read_rgba_span in swrast/s_span.c
> 
> inside _mesa_read_rgba_span: (*swrast->Driver.ReadRGBASpan) reads the
> correct r,g,b,a values, but then
> "if (buffer->UseSoftwareAlphaBuffers)" evaluates true and
> _mesa_read_alpha_span buggers the alpha values.
> 
> I saw in osmesa.c inside OSMesaCreateContextExt that there is a value
> "swalpha" set to GL_FALSE for RGBA buffers, but this value fails to make
> its way into osmesa->gl_buffer->UseSoftwareAlphaBuffers during the rest
> of the initialization. If during the init I manually set
> UseSoftwareAlphaBuffers to false, the blending looks OK and I think that
> the software uses a faster read function for the RGBA buffer in memory
> (havn't confirmed this yet).

I've just checked in a change to src/OSmesa/osmesa.c which should fix
this.  Please update your CVS tree and test.

Thanks for the bug report.

-Brian