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

[Eduardo Lima Mitev]

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