2 files changed, 48 insertions, 3 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_cc.c b/src/mesa/drivers/dri/i965/brw_cc.c
index d4ccd28c9e8..ab301b9a3a0 100644
--- a/src/mesa/drivers/dri/i965/brw_cc.c
+++ b/src/mesa/drivers/dri/i965/brw_cc.c
@@ -34,6 +34,7 @@
 #include "brw_state.h"
 #include "brw_defines.h"
 #include "brw_util.h"
+#include "intel_fbo.h"
 #include "main/macros.h"
 #include "main/enums.h"
 
@@ -89,6 +90,28 @@ struct brw_cc_unit_key {
    GLenum depth_func;
 };
 
+/**
+ * Modify blend function to force destination alpha to 1.0
+ *
+ * If \c function specifies a blend function that uses destination alpha,
+ * replace it with a function that hard-wires destination alpha to 1.0.  This
+ * is used when rendering to xRGB targets.
+ */
+static GLenum
+fix_xRGB_alpha(GLenum function)
+{
+   switch (function) {
+   case GL_DST_ALPHA:
+      return GL_ONE;
+
+   case GL_ONE_MINUS_DST_ALPHA:
+   case GL_SRC_ALPHA_SATURATE:
+      return GL_ZERO;
+   }
+
+   return function;
+}
+
 static void
 cc_unit_populate_key(struct brw_context *brw, struct brw_cc_unit_key *key)
 {
@@ -132,6 +155,17 @@ cc_unit_populate_key(struct brw_context *brw, struct brw_cc_unit_key *key)
       key->blend_dst_rgb = ctx->Color.BlendDstRGB;
       key->blend_src_a = ctx->Color.BlendSrcA;
       key->blend_dst_a = ctx->Color.BlendDstA;
+
+      /* If the renderbuffer is XRGB, we have to frob the blend function to
+       * force the destination alpha to 1.0.  This means replacing GL_DST_ALPHA
+       * with GL_ONE and GL_ONE_MINUS_DST_ALPAH with GL_ZERO.
+       */
+      if (ctx->Visual.alphaBits == 0) {
+	 key->blend_src_rgb = fix_xRGB_alpha(key->blend_src_rgb);
+	 key->blend_src_a   = fix_xRGB_alpha(key->blend_src_a);
+	 key->blend_dst_rgb = fix_xRGB_alpha(key->blend_dst_rgb);
+	 key->blend_dst_a   = fix_xRGB_alpha(key->blend_dst_a);
+      }
    }
 
    key->alpha_enabled = ctx->Color.AlphaEnabled;
diff --git a/src/mesa/drivers/dri/i965/brw_wm_surface_state.c b/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
index b7b6eaec2bb..74cf66f9f8b 100644
--- a/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
+++ b/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
@@ -538,11 +538,15 @@ brw_update_renderbuffer_surface(struct brw_context *brw,
 
       key.surface_type = BRW_SURFACE_2D;
       switch (irb->Base.Format) {
+      /* XRGB and ARGB are treated the same here because the chips in this
+       * family cannot render to XRGB targets.  This means that we have to
+       * mask writes to alpha (ala glColorMask) and reconfigure the alpha
+       * blending hardware to use GL_ONE (or GL_ZERO) for cases where
+       * GL_DST_ALPHA (or GL_ONE_MINUS_DST_ALPHA) is used.
+       */
       case MESA_FORMAT_ARGB8888:
-	 key.surface_format = BRW_SURFACEFORMAT_B8G8R8A8_UNORM;
-	 break;
       case MESA_FORMAT_XRGB8888:
-	 key.surface_format = BRW_SURFACEFORMAT_B8G8R8X8_UNORM;
+	 key.surface_format = BRW_SURFACEFORMAT_B8G8R8A8_UNORM;
 	 break;
       case MESA_FORMAT_RGB565:
 	 key.surface_format = BRW_SURFACEFORMAT_B5G6R5_UNORM;
@@ -579,6 +583,13 @@ brw_update_renderbuffer_surface(struct brw_context *brw,
    /* _NEW_COLOR */
    memcpy(key.color_mask, ctx->Color.ColorMask,
 	  sizeof(key.color_mask));
+
+   /* As mentioned above, disable writes to the alpha component when the
+    * renderbuffer is XRGB.
+    */
+   if (ctx->Visual.alphaBits == 0)
+     key.color_mask[3] = GL_FALSE;
+
    key.color_blend = (!ctx->Color._LogicOpEnabled &&
 		      ctx->Color.BlendEnabled);