[Mesa-dev] [PATCH 00/12] Computing GL versions without gl_context

[Emil Velikov]

On 03/08/14 18:26, Marek Olšák wrote:
> On Sun, Aug 3, 2014 at 6:44 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>> On 03/08/14 16:18, Marek Olšák wrote:
>>> Hi everyone,
>>>
>>> GLX_MESA_query_renderer can return supported GL versions before any context is created, but Gallium drivers and st/dri have not way to know which versions are supported, because the version computations take place in st/mesa at context creation.
>>>
>>> This patch series adjusts mesa/main, st/mesa, and st/dri to make computing all GL versions without a context possible. With this series, all supported GL versions (core, compatibility, ES1, ES2) are computed at DRIscreen (and pipe_screen) creation, which brings us closer to adding support for GLX_MESA_query_renderer.
>>>
>>> Please review.
>>>
>> Great work Marek,
>>
>> A ages ago when I initially looked at this I was thinking of extending (some
>> of) the extension/limits to be a API_OPENGL_LAST+1 sized array(s). This way we
>> don't need to do the {mesa,st}_init_{constants,extensions} dance four times.
>> The idea was to avoid making our glMakeCurrent even slower than it actually
>> is. Perhaps you shuffled things around and this is no longer relevant ?
> 
> I don't think so. I don't remember how MakeCurrent works, but I don't
> think this series has anything to do with it.
> 
Indeed. Seems like got the wrong function here.

>>
>> While there I was planning on deflating the size of gl_context (~150K) my
>> moving gl_constants (~1K) and gl_extensions (~0.2K) to DRIScreen, and storing
>> just a pointers in gl_context. This way we can avoid having yet another copy
>> of the constants (another ~0.2K) into glsl :) Yet I feel that all that is
>> slightly orthogonal to the original topic.
> 
> Actually, this series does make moving gl_extensions and gl_constants
> into DRIscreen a lot easier, assuming you would add separate copies of
> those structures for Core, Compat, ES1, and ES2. Then, we wouldn't
> have to do any feature checking at context creation.
> 
Indeed it does, yet my idea was bit different - keep the data in DRIscreen and
avoid copying it around. Just expand the specific limits/extensions (iirc only
10-20 of them need it) to store a value for each gl_api.

Ex. from st_init_extensions()

// Note the missing if (api == API_OPENGL_CORE)
consts->MaxViewports[API_OPENGL_CORE] =
      screen->get_param(screen, PIPE_CAP_MAX_VIEWPORTS);
if (consts->MaxViewports[API_OPENGL_CORE] >= 16) {
   consts->ViewportBounds[API_OPENGL_CORE].Min = -16384.0;
   consts->ViewportBounds[API_OPENGL_CORE.Max = 16384.0;
   extensions->ARB_viewport_array[API_OPENGL_CORE = GL_TRUE;
   extensions->ARB_fragment_layer_viewport[API_OPENGL_CORE] = GL_TRUE;
   if (extensions->AMD_vertex_shader_layer)
      extensions->AMD_vertex_shader_viewport_index[API_OPENGL_CORE] = GL_TRUE;
   }

As such one will need to call st_init_extensions() only once :) Yet I fear it
may look a bit messy.

Anywho, all that can be done as a follow-up if anyone is interested.

Thanks again,
Emil

> Marek
>