Philipp Klaus Krause wrote:
Stephane Marchesin schrieb:
What is the point of advertising GL_MESA_pack_invert if it's not
implemented ?
Stephane
According to extensions specification this extension's main purpose
seems to be making application developers life a little bit easier, just
like GL_MESA_window_pos/GL_ARB_window_pos does, not exposing hardware
features. So I thought it might be useful to advertize this one.
The i915 driver does the same.
The intel driver actually uses it however - if you set that PACK_INVERT
parameter the driver will do optimized pixel reads (i.e. direct blits).
I don't see much point in advertizing vendor-speficic extensions if the
hardware doesn't support it natively (that's not to say the r128
wouldn't support GL_MESA_pack_invert in hardware, but you'd need to
implement optimized pixel readback functions to take advantage of it).
In that sense, I'd consider NV_vertex_program as bloat just as well.
Applications really always can deal with not available non-standard
extensions very well.
There's some point for adding the ARB (and EXT) extensions, though
actually ARB_vertex_program doesn't come for free. Vertex programs are
slow currently, so if an app would use a fixed-function fallback it
would likely be faster. Though of course not everything possible with
ARB_vertex_program can be done with fixed function... (and in theory
vertex programs could be just as fast as fixed function when done in
software, it's just currently not the case with mesa).
Roland
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