From 0b90ffd534ff592b71190f4a6f779e32be4b534e Mon Sep 17 00:00:00 2001
From: Gurchetan Singh <gurchetansingh@chromium.org>
Date: Fri, 22 Apr 2016 10:29:56 -0700
Subject: [PATCH] CHROMIUM: mesa: Remove code that returns a desktop GL enum

When the draw_buffer_enum_to_bitmask function
is called while Mesa is in it's meta state,
the wrong GLbitfield is returned sometimes for
OpenGL ES contexts.  This is because the
_mesa_meta_begin function makes the ctx->API always
equal to desktop GL during the meta state.

In the case of GL_BACK, the _mesa_is_gles(ctx)
function is checked when returning the enum.
This check evaluates to false during the meta state,
even on mobile devices.

BUG=b/27656575
TEST=Ran dEQP-GLES2.functional.clipping.line.line_attrib_clip
with the pbuffer option with on Cyan.  Verified it
fails without the patch.

Signed-off-by: Tomasz Figa <tfiga@chromium.org>
---
 src/mesa/main/buffers.c | 39 ++++++++++++++++++---------------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/src/mesa/main/buffers.c b/src/mesa/main/buffers.c
index a28c583..36dbc8c 100644
--- a/src/mesa/main/buffers.c
+++ b/src/mesa/main/buffers.c
@@ -97,27 +97,24 @@ draw_buffer_enum_to_bitmask(const struct gl_context *ctx, GLenum buffer)
       case GL_FRONT:
          return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_FRONT_RIGHT;
       case GL_BACK:
-         if (_mesa_is_gles(ctx)) {
-            /* Page 181 (page 192 of the PDF) in section 4.2.1 of the OpenGL
-             * ES 3.0.1 specification says:
-             *
-             *     "When draw buffer zero is BACK, color values are written
-             *     into the sole buffer for single-buffered contexts, or into
-             *     the back buffer for double-buffered contexts."
-             *
-             * Since there is no stereo rendering in ES 3.0, only return the
-             * LEFT bits.  This also satisfies the "n must be 1" requirement.
-             *
-             * We also do this for GLES 1 and 2 because those APIs have no
-             * concept of selecting the front and back buffer anyway and it's
-             * convenient to be able to maintain the magic behaviour of
-             * GL_BACK in that case.
-             */
-            if (ctx->DrawBuffer->Visual.doubleBufferMode)
-               return BUFFER_BIT_BACK_LEFT;
-            return BUFFER_BIT_FRONT_LEFT;
-         }
-         return BUFFER_BIT_BACK_LEFT | BUFFER_BIT_BACK_RIGHT;
+         /* Page 181 (page 192 of the PDF) in section 4.2.1 of the OpenGL
+          * ES 3.0.1 specification says:
+          *
+          *     "When draw buffer zero is BACK, color values are written
+          *     into the sole buffer for single-buffered contexts, or into
+          *     the back buffer for double-buffered contexts."
+          *
+          * Since there is no stereo rendering in ES 3.0, only return the
+          * LEFT bits.  This also satisfies the "n must be 1" requirement.
+          *
+          * We also do this for GLES 1 and 2 because those APIs have no
+          * concept of selecting the front and back buffer anyway and it's
+          * convenient to be able to maintain the magic behaviour of
+          * GL_BACK in that case.
+          */
+         if (ctx->DrawBuffer->Visual.doubleBufferMode)
+            return BUFFER_BIT_BACK_LEFT;
+         return BUFFER_BIT_FRONT_LEFT;
       case GL_RIGHT:
          return BUFFER_BIT_FRONT_RIGHT | BUFFER_BIT_BACK_RIGHT;
       case GL_FRONT_RIGHT:
-- 
2.1.2