geometry shaders: make gs work with changable primitives and variable number of vertices

lots and lots of fixes for geometry shaders. in particular now we work when the gs
emits a different primitive than the one the pipeline was started with and also
we work when gs emits more vertices than would fit in the original buffer.

1 files changed, 15 insertions, 7 deletions

diff --git a/src/gallium/auxiliary/draw/draw_gs.h b/src/gallium/auxiliary/draw/draw_gs.h
index d8eb210343..6a9800c43f 100644
--- a/src/gallium/auxiliary/draw/draw_gs.h
+++ b/src/gallium/auxiliary/draw/draw_gs.h
@@ -54,18 +54,26 @@ struct draw_geometry_shader {
    unsigned input_primitive;
    unsigned output_primitive;
 
+   unsigned emitted_vertices;
+   unsigned emitted_primitives;
+
    /* Extracted from shader:
     */
    const float (*immediates)[4];
 };
 
-void draw_geometry_shader_run(struct draw_geometry_shader *shader,
-                              const float (*input)[4],
-                              float (*output)[4],
-                              const void *constants[PIPE_MAX_CONSTANT_BUFFERS],
-                              unsigned count,
-                              unsigned input_stride,
-                              unsigned output_stride);
+/*
+ * Returns the number of vertices emitted.
+ * The vertex shader can emit any number of vertices as long as it's
+ * smaller than the GS_MAX_OUTPUT_VERTICES shader property.
+ */
+int draw_geometry_shader_run(struct draw_geometry_shader *shader,
+                             const float (*input)[4],
+                             float (*output)[4],
+                             const void *constants[PIPE_MAX_CONSTANT_BUFFERS],
+                             unsigned count,
+                             unsigned input_stride,
+                             unsigned output_stride);
 
 void draw_geometry_shader_prepare(struct draw_geometry_shader *shader,
                                   struct draw_context *draw);