i965: glClearBuffer() should only clear a single buffer.

glClearBuffer() is currently clearing all active draw color buffers (all
buffers that have not been set to GL_NONE when calling glDrawBuffers) instead
of only clearing the one it receives as parameter. Altough brw_clear()
receives a bit mask indicating the color buffers that should be cleared,
this mask is ignored when calling brw_blorp_clear_color().

This was breaking the 'fbo-drawbuffers-none glClearBuffer' piglit test.

The patch provides the bit mask to brw_blorp_clear_color() so it can limit
clearing to the color buffers present in the mask.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76832
Reviewed-by: Eric Anholt <eric@anholt.net>

3 files changed, 7 insertions, 3 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_blorp.h b/src/mesa/drivers/dri/i965/brw_blorp.h
index db41497732e..15a7a0b552b 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp.h
+++ b/src/mesa/drivers/dri/i965/brw_blorp.h
@@ -48,7 +48,7 @@ brw_blorp_blit_miptrees(struct brw_context *brw,
 
 bool
 brw_blorp_clear_color(struct brw_context *brw, struct gl_framebuffer *fb,
-                      bool partial_clear);
+                      GLbitfield mask, bool partial_clear);
 
 void
 brw_blorp_resolve_color(struct brw_context *brw,
diff --git a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
index 851af8cadb8..0b13bf1331b 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
+++ b/src/mesa/drivers/dri/i965/brw_blorp_clear.cpp
@@ -567,12 +567,16 @@ do_single_blorp_clear(struct brw_context *brw, struct gl_framebuffer *fb,
 extern "C" {
 bool
 brw_blorp_clear_color(struct brw_context *brw, struct gl_framebuffer *fb,
-                      bool partial_clear)
+                      GLbitfield mask, bool partial_clear)
 {
    for (unsigned buf = 0; buf < fb->_NumColorDrawBuffers; buf++) {
       struct gl_renderbuffer *rb = fb->_ColorDrawBuffers[buf];
       struct intel_renderbuffer *irb = intel_renderbuffer(rb);
 
+      /* Only clear the buffers present in the provided mask */
+      if (((1 << fb->_ColorDrawBufferIndexes[buf]) & mask) == 0)
+         continue;
+
       /* If this is an ES2 context or GL_ARB_ES2_compatibility is supported,
        * the framebuffer can be complete with some attachments missing.  In
        * this case the _ColorDrawBuffers pointer will be NULL.
diff --git a/src/mesa/drivers/dri/i965/brw_clear.c b/src/mesa/drivers/dri/i965/brw_clear.c
index a487a71838f..ee8f54fec54 100644
--- a/src/mesa/drivers/dri/i965/brw_clear.c
+++ b/src/mesa/drivers/dri/i965/brw_clear.c
@@ -245,7 +245,7 @@ brw_clear(struct gl_context *ctx, GLbitfield mask)
    /* BLORP is currently only supported on Gen6+. */
    if (brw->gen >= 6 && brw->gen < 8) {
       if (mask & BUFFER_BITS_COLOR) {
-         if (brw_blorp_clear_color(brw, fb, partial_clear)) {
+         if (brw_blorp_clear_color(brw, fb, mask, partial_clear)) {
             debug_mask("blorp color", mask & BUFFER_BITS_COLOR);
             mask &= ~BUFFER_BITS_COLOR;
          }