Re: [Mesa-dev] [PATCH] st/mesa: DrawTFB should use the vertex count from the last call of EndTFB

[Brian Paul]

On 12/17/2011 06:41 AM, Marek Olšák wrote:
 From ARB_transform_feedback2:
     ... the vertex count used for the rendering operation is
     set by the previous EndTransformFeedback command.
---
  src/mesa/state_tracker/st_cb_xformfb.c |   53 +++++++++++++++++++++++++------
  1 files changed, 42 insertions(+), 11 deletions(-)
diff --git a/src/mesa/state_tracker/st_cb_xformfb.c 
b/src/mesa/state_tracker/st_cb_xformfb.c
index 2fc28dc..e699fb6 100644
--- a/src/mesa/state_tracker/st_cb_xformfb.c
+++ b/src/mesa/state_tracker/st_cb_xformfb.c
@@ -55,6 +55,11 @@ struct st_transform_feedback_object {

     unsigned num_targets;
     struct pipe_stream_output_target *targets[PIPE_MAX_SO_BUFFERS];
+
+   /* This encapsulates the count that can be used as a source for draw_vbo.
+    * It contains a stream output target from the last call of
+    * EndTransformFeedback. */
+   struct pipe_stream_output_target *draw_count;
  };


@@ -81,6 +86,8 @@ st_delete_transform_feedback(struct gl_context *ctx,
           (struct st_transform_feedback_object*)obj;
     unsigned i;

+   pipe_so_target_reference(&sobj->draw_count, NULL);
+
     /* Unreference targets. */
     for (i = 0; i<  sobj->num_targets; i++) {
        pipe_so_target_reference(&sobj->targets[i], NULL);
@@ -115,6 +122,7 @@ st_begin_transform_feedback(struct gl_context *ctx, GLenum 
mode,
        if (bo) {
           /* Check whether we need to recreate the target. */
           if (!sobj->targets[i] ||
+             sobj->targets[i] == sobj->draw_count ||
               sobj->targets[i]->buffer != bo->buffer ||
               sobj->targets[i]->buffer_offset != sobj->base.Offset[i] ||
               sobj->targets[i]->buffer_size != sobj->base.Size[i]) {
@@ -141,7 +149,7 @@ st_begin_transform_feedback(struct gl_context *ctx, GLenum 
mode,


  static void
-st_stop_transform_feedback(struct gl_context *ctx,
+st_pause_transform_feedback(struct gl_context *ctx,
                             struct gl_transform_feedback_object *obj)
  {
     struct st_context *st = st_context(ctx);
@@ -161,11 +169,9 @@ st_resume_transform_feedback(struct gl_context *ctx,
                            ~0);
  }

-/* Set count_from_stream_output to any stream output target
- * from the transform feedback object. */
-void
-st_transform_feedback_draw_init(struct gl_transform_feedback_object *obj,
-                                struct pipe_draw_info *out)
+
+static struct pipe_stream_output_target *
+st_transform_feedback_get_draw_target(struct gl_transform_feedback_object *obj)
  {
     struct st_transform_feedback_object *sobj =
           (struct st_transform_feedback_object*)obj;
@@ -173,13 +179,38 @@ st_transform_feedback_draw_init(struct 
gl_transform_feedback_object *obj,

     for (i = 0; i<  Elements(sobj->targets); i++) {
        if (sobj->targets[i]) {
-         out->count_from_stream_output = sobj->targets[i];
-         return;
+         return sobj->targets[i];
        }
     }

     assert(0);
-   out->count_from_stream_output = NULL;
+   return NULL;
+}
+
+
+static void
+st_end_transform_feedback(struct gl_context *ctx,
+                          struct gl_transform_feedback_object *obj)
+{
+   struct st_context *st = st_context(ctx);
+   struct st_transform_feedback_object *sobj =
+         (struct st_transform_feedback_object*)obj;
+
+   cso_set_stream_outputs(st->cso_context, 0, NULL, 0);
+
+   pipe_so_target_reference(&sobj->draw_count,
+                            st_transform_feedback_get_draw_target(obj));
+}
+
+
+void
+st_transform_feedback_draw_init(struct gl_transform_feedback_object *obj,
+                                struct pipe_draw_info *out)
+{
+   struct st_transform_feedback_object *sobj =
+         (struct st_transform_feedback_object*)obj;
+
+   out->count_from_stream_output = sobj->draw_count;
  }

Minor nit: instead of using casts for st_transform_feedback_object, 
define a cast wrapper as we do for other types:

static INLINE struct st_transform_feedback_object *
st_transform_feedback_object(struct gl_transform_feedback_object *obj)
{
   return (struct st_transform_feedback_object *) obj;
}


Looks good otherwise.



@@ -189,8 +220,8 @@ st_init_xformfb_functions(struct dd_function_table 
*functions)
     functions->NewTransformFeedback = st_new_transform_feedback;
     functions->DeleteTransformFeedback = st_delete_transform_feedback;
     functions->BeginTransformFeedback = st_begin_transform_feedback;
-   functions->EndTransformFeedback = st_stop_transform_feedback;
-   functions->PauseTransformFeedback = st_stop_transform_feedback;
+   functions->EndTransformFeedback = st_end_transform_feedback;
+   functions->PauseTransformFeedback = st_pause_transform_feedback;
     functions->ResumeTransformFeedback = st_resume_transform_feedback;
  }


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