On 03/27/2012 10:31 AM, Ian Romanick wrote:
On 03/26/2012 01:35 PM, Eric Anholt wrote:
I've got a question for GLSL 1.40 that could use some interpretation:
Section 1.2.5 in the spec says:
"The following features, previously deprecated, are removed:
...
Fixed functionality for a programmable stage. Supply shaders for
all stages currently being used."
What exactly does this mean? Undefined results? Link error? Draw
time error? I couldn't find anything explicit in the 3.1 core spec
(since it doesn't have fixed function, so it doesn't really explain
interaction with it) or the compat spec (since it has
ARB_compatibility, so that deprecated functionality is re-allowed).
At the bottom of that list is also the line:
"Removed features were recast under the ARB_compatibility
extension, within this specification."
I believe this implies the same link error as in ES 2.0. The wording is
weird. I thought we ended up saying something more clear than this, but
it was a long time ago.
I think my resolution would be: Don't expose GLSL 1.40 outside of a GL
3.1+ core context, thus dodging the question of how to interact between
the FF and GLSL 1.40 without GL_ARB_compatibility exposed.
I think that's reasonable. Though, this may lead to people wanting
EXT_gpu_shader4 to get UBOs in some apps. I guess we can cross that
bridge when we come to it.
There is also a requirement that shaders from different stage must have
the same version. We could just enable the same all-stages linker check
if any stage is 1.40 that we already have for ES shaders.
It's not a huge deal to me either way.
Yeah, I think the linker needs to mandate all stages be present, like
ES. That said, I'm still unclear what happens if you do a draw call
without a UseProgram. Undefined results? GL error?
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