On 01/20/2012 04:12 AM, Christoph Bumiller wrote:
On 20.01.2012 12:45, Henri Verbeet wrote:
On 20 January 2012 03:24, Eric Anholt<e...@anholt.net> wrote:
So is it also allowed to blit from S8Z24 to Z24S8 ? Could we also allow
to blit from RGBA8 to BGRA8 then, please ?
That's already allowed.
Yeah, but not for multisampled framebuffers, unless RGBA8 and BGRA8
are considered identical (ARB_fbo):
If SAMPLE_BUFFERS for either the read framebuffer or
draw framebuffer is greater than zero, no copy is performed and an
INVALID_OPERATION error is generated if the dimensions of the source
and destination rectangles provided to BlitFramebuffer are not
identical, or if the formats of the read and draw framebuffers are
not identical.
Yes, sorry, I didn't realize this only applied to multisample buffers.
I just tested again and the blob conveniently ignores the matching
formats condition altogether.
The point is that I'd really like to support GL_RGBA8 as red-first,
regardless of the window format.
There might even be window systems that force either the one or the
other, and then we could never be compatible with both and support the
established behaviour of NOT doing 2 blits (first to temporary
framebuffer where we can be sure the format matches and then to the
window) when resolving.
I discussed this with some people in Khronos, and I've been convinced
that we're slightly misinterpreting the spec on this topic. The
behavior mentioned in the spec is concerned with the internalFormat (and
the GL-selected internalFormat) supplied to glRenderbufferStorage and
friends. In this case, BGRA is *not* an internalFormat that an
application can request. A driver can choose to use that ordering, but
it should be transparent to the application.
All of the possible formats are in table 3.16 and table 4.11 in the
OpenGL 3.0 spec.
Based on that, I think we should treat all of the permutations of RGBAn
as equivalent. That is, MESA_FORMAT_ARGB8888 can blit to
MESA_FORMAT_ARGB8888_REV can blit to
MESA_FORMAT_RGBA8888 because the all map to RGBA8 in table 3.16. If we
had a function that could map a MESA_FORMAT_ back to a GL
internalFormat, we could just compare those.
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