[Mesa-dev] [PATCH 3/4] meta: Add flag MESA_META_SELECT_FEEDBACK

[Chad Versace]

On 10/07/2011 04:45 PM, Chad Versace wrote:
> On 10/07/2011 04:23 PM, Brian Paul wrote:
>> On 10/07/2011 04:55 PM, Chad Versace wrote:
>>> If this flag is set, then _mesa_meta_begin will save/restore the state of
>>> GL_SELECT and GL_FEEDBACK render modes.
>>>
>>> Intel's futue resolve meta-ops will require this, since buffer resolves
>>> may occur when the GL_RENDER_MODE is GL_SELECT.
>>>
>>> Signed-off-by: Chad Versace<chad at chad-versace.us>
>>> ---
>>>   src/mesa/drivers/common/meta.c |   26 ++++++++++++++++++++++++++
>>>   src/mesa/drivers/common/meta.h |    1 +
>>>   2 files changed, 27 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
>>> index 5b73dcd..fc25f92 100644
>>> --- a/src/mesa/drivers/common/meta.c
>>> +++ b/src/mesa/drivers/common/meta.c
>>> @@ -172,6 +172,11 @@ struct save_state
>>>      struct gl_query_object *CondRenderQuery;
>>>      GLenum CondRenderMode;
>>>
>>> +   /** MESA_META_SELECT_FEEDBACK */
>>> +   GLenum RenderMode;
>>> +   struct gl_selection Select;
>>> +   struct gl_feedback Feedback;
>>> +
>>>      /** Miscellaneous (always disabled) */
>>>      GLboolean Lighting;
>>>   };
>>> @@ -608,6 +613,17 @@ _mesa_meta_begin(struct gl_context *ctx, GLbitfield state)
>>>        _mesa_EndConditionalRender();
>>>      }
>>>
>>> +   if (state&  MESA_META_SELECT_FEEDBACK) {
>>> +      save->RenderMode = ctx->RenderMode;
>>> +      if (ctx->RenderMode == GL_SELECT) {
>>> +     save->Select = ctx->Select; /* struct copy */
>>> +     _mesa_RenderMode(GL_RENDER);
>>> +      } else if (ctx->RenderMode == GL_FEEDBACK) {
>>> +     save->Feedback = ctx->Feedback; /* struct copy */
>>> +     _mesa_RenderMode(GL_RENDER);
>>> +      }
>>> +   }
>>> +
>>>      /* misc */
>>>      {
>>>         save->Lighting = ctx->Light.Enabled;
>>> @@ -893,6 +909,16 @@ _mesa_meta_end(struct gl_context *ctx)
>>>                         save->CondRenderMode);
>>>      }
>>>
>>> +   if (state&  MESA_META_SELECT_FEEDBACK) {
>>> +      if (save->RenderMode == GL_SELECT) {
>>> +     ctx->Select = save->Select;
>>> +     _mesa_RenderMode(GL_SELECT);
>>> +      } else if (save->RenderMode == GL_FEEDBACK) {
>>> +     ctx->Feedback = save->Feedback;
>>> +     _mesa_RenderMode(GL_FEEDBACK);
>>> +      }
>>> +   }
>>
>> You might need to switch the order of calling _mesa_RenderMode() and assigning the ctx->Feedback/Select state.  That is:
>>
>>      _mesa_RenderMode(GL_FEEDBACK);
>>      ctx->Feedback = save->Feedback;
> 
> My intuition also thought this was the correct order. But a Piglit test proved my intuition wrong.
>>
>> I presume that after _mesa_meta_end() is called, we want the selection/feedback state to be just as it was before _mesa_meta_begin() was called, right?
> 
> Right.
>  
>> When _mesa_RenderMode() is called it mucks with various ctx->Select or ctx->Feedback fields.  So we need to assign/restore the old ctx->Select/Feedback state _after_ that if we want to restore things just as they were.
>>
>> What do you think?
>>
>> -Brian
> 
> _mesa_RenderMode clobbers and checks the state like this:
>     current mode    new mode      clobbers                asserts
>     --------------------------------------------------------------
>     RENDER          *             nothing 
>     SELECT          *             ctx.Select
>     FEEDBACK        *             ctx.Feedback.Count
>     *               RENDER                                nothing
>     *               SELECT                                ctx.Select.BufferSize > 0
>     *               FEEDBACK                              ctx.Feedback.BufferSize > 0
>  
> So in meta_begin, we need to save the state before calling glRenderMode in order to prevent the state from getting clobbered. And in meta_end, we need to restore the state before calling glRenderMode in order to prevent the assertions from failing.


Silly me. My brain was tied in a knot. I see your point now. The second hunk should be changed to this:

@@ -893,6 +909,16 @@ _mesa_meta_end(struct gl_context *ctx)
                        save->CondRenderMode);
     }

+   if (state&  MESA_META_SELECT_FEEDBACK) {
+      if (save->RenderMode == GL_SELECT) {
+         _mesa_RenderMode(GL_SELECT);
+         ctx->Select = save->Select;
+      } else if (save->RenderMode == GL_FEEDBACK) {
+         _mesa_RenderMode(GL_FEEDBACK);
+         ctx->Feedback = save->Feedback;
+      }
+   }

-- 
Chad Versace
chad at chad-versace.us