[Mesa-dev] [PATCH V3 05/13] mesa: Add validation helpers for new indirect draws

[Chris Forbes]

Ken,

I don't have access to another implementation at the moment -- can you test?

-- Chris

On Wed, Nov 13, 2013 at 9:57 AM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> On 11/12/2013 12:35 PM, Paul Berry wrote:
>> On 12 November 2013 12:13, Kenneth Graunke <kenneth at whitecape.org
>> <mailto:kenneth at whitecape.org>> wrote:
>>
>>     It would be great to put a citation for this:
>>
>>     /* From the ARB_multi_draw_indirect specification:
>>      * "INVALID_VALUE is generated by MultiDrawArraysIndirect or
>>      *  MultiDrawElementsIndirect if <primcount> is negative."
>>      *
>>      * "<primcount> must be positive, otherwise an INVALID_VALUE error will
>>      *  be generated."
>>      */
>>
>>     These beg the question of whether 0 is allowed.  Usually I interpret
>>     "negative" as < 0, "positive" as >= 0, and "strictly positive" as > 0.
>>     So I think zero should be allowed, and I don't see a contradiction.
>>
>>     The only text I can find in 4.3 and 4.4 just reiterate that it needs to
>>     positive, and I don't see any text defining "positive."
>>
>>
>> In the absence of text defining "positive", shouldn't we go with the
>> definition used by mathematicians?  According to
>> http://en.wikipedia.org/wiki/Sign_%28mathematics%29#Terminology_for_signs,
>> "positive" means strictly greater than zero.
>
> Mathematicians are inconsistent in their use of terminology.  Positive
> can mean either > 0 or >= 0 depending who you talk to and in what
> context.  And the GL specification authors are notoriously non-precise.
>
>> If anyone is aware of a competing implementation that accepts a
>> primcount of 0, then I'd be open to following the behaviour of the
>> competing implementation (and filing a spec bug).  But otherwise I think
>> we should prohibit zero.
>
> Then I suppose I have to go test AMD or nVidia.
>
>> (Note: I brought this up last time the patch was reviewed:
>> http://lists.freedesktop.org/archives/mesa-dev/2013-November/047962.html)