[Mesa-dev] [PATCH] st/mesa: fail to draw instead of asserting in transform feedback

[Marek Olšák]

It's not a failure, so it can't _fail_ to draw. It should be
interpreted such that the drawing succeeds with the vertex count given
by the transform feedback object, which is 0.

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Thu, Jul 30, 2015 at 12:46 PM, Dave Airlie <airlied at gmail.com> wrote:
> if we get a request to take the count from feedback, but there
> is no buffer to take it from, just draw nothing instead of asserting.
>
> This fixes this assert killing the ogl conform, and a piglit
> test I've sent.
>
> Signed-off-by: Dave Airlie <airlied at redhat.com>
> ---
>  src/mesa/state_tracker/st_cb_xformfb.c | 6 ++++--
>  src/mesa/state_tracker/st_cb_xformfb.h | 2 +-
>  src/mesa/state_tracker/st_draw.c       | 3 ++-
>  3 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/src/mesa/state_tracker/st_cb_xformfb.c b/src/mesa/state_tracker/st_cb_xformfb.c
> index 07c118e..0708e68 100644
> --- a/src/mesa/state_tracker/st_cb_xformfb.c
> +++ b/src/mesa/state_tracker/st_cb_xformfb.c
> @@ -191,7 +191,6 @@ st_transform_feedback_get_draw_target(struct gl_transform_feedback_object *obj)
>        }
>     }
>
> -   assert(0);
>     return NULL;
>  }
>
> @@ -211,14 +210,17 @@ st_end_transform_feedback(struct gl_context *ctx,
>  }
>
>
> -void
> +bool
>  st_transform_feedback_draw_init(struct gl_transform_feedback_object *obj,
>                                  struct pipe_draw_info *out)
>  {
>     struct st_transform_feedback_object *sobj =
>           st_transform_feedback_object(obj);
>
> +   if (sobj->draw_count == NULL)
> +      return false;
>     out->count_from_stream_output = sobj->draw_count;
> +   return true;
>  }
>
>
> diff --git a/src/mesa/state_tracker/st_cb_xformfb.h b/src/mesa/state_tracker/st_cb_xformfb.h
> index 998c418..fb50ded 100644
> --- a/src/mesa/state_tracker/st_cb_xformfb.h
> +++ b/src/mesa/state_tracker/st_cb_xformfb.h
> @@ -38,7 +38,7 @@ struct pipe_draw_info;
>  extern void
>  st_init_xformfb_functions(struct dd_function_table *functions);
>
> -extern void
> +extern bool
>  st_transform_feedback_draw_init(struct gl_transform_feedback_object *obj,
>                                  struct pipe_draw_info *out);
>
> diff --git a/src/mesa/state_tracker/st_draw.c b/src/mesa/state_tracker/st_draw.c
> index 66b2f83..bae8096 100644
> --- a/src/mesa/state_tracker/st_draw.c
> +++ b/src/mesa/state_tracker/st_draw.c
> @@ -242,7 +242,8 @@ st_draw_vbo(struct gl_context *ctx,
>        /* Transform feedback drawing is always non-indexed. */
>        /* Set info.count_from_stream_output. */
>        if (tfb_vertcount) {
> -         st_transform_feedback_draw_init(tfb_vertcount, &info);
> +         if (st_transform_feedback_draw_init(tfb_vertcount, &info) == false)
> +            return;
>        }
>     }
>
> --
> 2.4.3
>
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