[Mesa-dev] [PATCH v2] mesa: Initializes the stencil value masks to 0xFF instead of ~0u

[Olivier Galibert]

Note that ~0U is perfectly correct w.r.t the GLES3 spec.  It just
means that s=32, which happens to be greater or equal to 8.

Best,

  OG.


On Tue, Dec 16, 2014 at 8:58 AM, Eduardo Lima Mitev <elima at igalia.com> wrote:
> On 12/15/2014 08:30 PM, Ian Romanick wrote:
>> On 12/15/2014 08:04 AM, Eduardo Lima Mitev wrote:
>>>
>>> Since the maximum supported precision for stencil buffers is 8 bits, mask
>>> values should be initialized to 2^8 - 1 = 0xFF.
>>>
>>> Currently, these masks are initialized to max unsigned integer (~0u), which
>>> causes their values to overflow to -1 when converted to signed int by glGet* APIs.
>>
>> I did some research on this... before desktop OpenGL 3.1, the spec said
>> something quite different.  Please add the following to the commit message:
>>
>> "In OpenGL 3.0 and before, the an initial value of ~0u was specified:
>>
>>     In the initial state, stenciling is disabled, the front and back
>>     stencil reference value are both zero, the front and back stencil
>>     comparison functions are both ALWAYS, and the front and back
>>     stencil mask are both all ones."
>>
>
> Oh, interesting. I should have looked back into older specs to
> understand where the ~0u was coming from. Note taken.
>
>>
>> With that, this patch is
>>
>> Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
>>
>
> Great. If you feel like nitpicking, you can check the final commit log
> here:
> https://github.com/Igalia/mesa/commit/3784f7b2d5aa739c4abf9aa28874b85bbd1550e5
>
> Thanks a lot!
>
> Eduardo
>
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