[Mesa-dev] Gallium: Removal of set_index_buffer (discussion)

[Marek Olšák]

Hi,

I'd like to remove pipe_context::set_index_buffer. It's not useful to
most drivers and the interface is inconvenient for Mesa/OpenGL,
because it's a draw state that is set with a separate driver callback,
which is an unnecessary driver roundtrip taking some CPU cycles. I'd
prefer to pass the index buffer via pipe_draw_info.

I'm aware that the interface was inherited from DX10, but I don't
think that makes any difference here. DX10 state trackers can pass the
index buffer via pipe_draw_info too.

This is my proposal:

iff --git a/src/gallium/include/pipe/p_state.h
b/src/gallium/include/pipe/p_state.h
index ce19b92..cffbb33 100644
--- a/src/gallium/include/pipe/p_state.h
+++ b/src/gallium/include/pipe/p_state.h
@@ -635,7 +635,7 @@ struct pipe_index_buffer
  */
 struct pipe_draw_info
 {
-   boolean indexed;  /**< use index buffer */
+   ubyte index_size;  /**< 0 = non-indexed */
    enum pipe_prim_type mode;  /**< the mode of the primitive */
    boolean primitive_restart;
    ubyte vertices_per_patch; /**< the number of vertices per patch */
@@ -666,12 +666,18 @@ struct pipe_draw_info

    unsigned indirect_params_offset; /**< must be 4 byte aligned */

+   /**
+    * Index buffer. Only one can be non-NULL.
+    */
+   struct pipe_resource *index_buffer; /* "start" is the offset */
+   void *user_indices;
+
    /* Pointers must be at the end for an optimal structure layout on 64-bit. */


Comments welcome,

Marek