gallium: allow choosing which colorbuffers to clear

Required for glClearBuffer, which only clears one colorbuffer attachment.

Example:
   If the first colorbuffer is float and the second one is int:
      pipe->clear(pipe, PIPE_CLEAR_COLOR0, float_clear_color, ...);
      pipe->clear(pipe, PIPE_CLEAR_COLOR1, int_clear_color, ...);

This doesn't need any driver changes yet, because all drivers just use:
  if (flags & PIPE_CLEAR_COLOR) ..

The drivers which support GL 3.0 will have to implement it properly though.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/gallium/auxiliary/util/u_clear.h b/src/gallium/auxiliary/util/u_clear.h
index e9fd874b1fc..75047c16b93 100644
--- a/src/gallium/auxiliary/util/u_clear.h
+++ b/src/gallium/auxiliary/util/u_clear.h
@@ -42,9 +42,10 @@ util_clear(struct pipe_context *pipe,
            struct pipe_framebuffer_state *framebuffer, unsigned buffers,
            const union pipe_color_union *color, double depth, unsigned stencil)
 {
-   if (buffers & PIPE_CLEAR_COLOR) {
-      unsigned i;
-      for (i = 0; i < framebuffer->nr_cbufs; i++) {
+   unsigned i;
+
+   for (i = 0; i < framebuffer->nr_cbufs; i++) {
+      if (buffers & (PIPE_CLEAR_COLOR0 << i)) {
          struct pipe_surface *ps = framebuffer->cbufs[i];
          pipe->clear_render_target(pipe, ps, color, 0, 0, ps->width, ps->height);
       }