draw: keep record of number of active vertex buffers

src/gallium/auxiliary/draw/draw_context.c

@@ -249,6 +249,7 @@ draw_set_vertex_buffers(struct draw_context *draw,
    draw_do_flush( draw, DRAW_FLUSH_VERTEX_CACHE/*STATE_CHANGE*/ );
 
    memcpy(draw->vertex_buffer, buffers, count * sizeof(buffers[0]));
+   draw->nr_vertex_buffers = count;
 }
 
 

src/gallium/auxiliary/draw/draw_private.h

@@ -245,7 +245,10 @@ struct draw_context
    /* pipe state that we need: */
    const struct pipe_rasterizer_state *rasterizer;
    struct pipe_viewport_state viewport;
+
    struct pipe_vertex_buffer vertex_buffer[PIPE_MAX_ATTRIBS];
+   unsigned nr_vertex_buffers;
+
    struct pipe_vertex_element vertex_element[PIPE_MAX_ATTRIBS];
    struct draw_vertex_shader *vertex_shader;