(In reply to Roland Scheidegger from comment #94)
> Created attachment 120734 [details] [review] [review]
> apitrace patch for honoring range in DrawRangeElementsX commands
> 
> So you'd want something like this (totally untested) patch for apitrace?
> Makes sense I guess that the specified range not only means the supplied
> indices have to be inside that range, but it also works the other way round
> (driver can rely on the specified range being accessible) - otherwise the
> driver would still need to scan the actual index buffer. (Albeit since for
> this app the ranges seem to be pretty bogus who knows if the memory inside
> the specified range but not used in the actual indices is really always
> accessible.)

Yes, this does indeed make sense.

For VBOs, the start/end range is a hint (the OpenGL shouldn't crash if the
start/end range goes beyond the VBO size), but for user memory arrays, there's
no reliable way to know where user memory is supposed to stop -- the start/end
range is it.

> I am actually wondering if it would be legal if the memory isn't accessible
> below the start value (apitrace surely couldn't handle that)...

I don't think it's worth worrying about that.