Mesa (master): mesa: Allow glReadBuffer(GL_NONE) for winsys framebuffers.

[Paul Berry]

Module: Mesa
Branch: master
Commit: cf5632094ba0c19d570ea47025cf6da75ef8457a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=cf5632094ba0c19d570ea47025cf6da75ef8457a

Author: Paul Berry <stereotype441 at gmail.com>
Date:   Wed Dec 19 10:08:58 2012 -0800

mesa: Allow glReadBuffer(GL_NONE) for winsys framebuffers.

Previously, Mesa code assumed that glReadBuffer(GL_NONE) was only
valid for user-created framebuffer objects.  However, the spec is
quite clear that is should also be valid for the default framebuffer.
>From section 18.2.1 ("Obtaining Pixels from the Framebuffer") of the
GL 4.3 spec:

    "When READ_FRAMEBUFFER_BINDING is zero, i.e. the default
    framebuffer, src must be one of the values listed in table 17.4,
    including NONE."

Similar language exists in the GLES 3.0 spec, and in desktop GL all
the way back to ARB_framebuffer_object.

Partially fixes GLES3 conformance test "CoverageES30.test".

NOTE: This is a candidate for stable branches.

Reviewed-by: Eric Anholt <eric at anholt.net>
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

---

 src/mesa/main/buffers.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/mesa/main/buffers.c b/src/mesa/main/buffers.c
index 76f0d46..d10a573 100644
--- a/src/mesa/main/buffers.c
+++ b/src/mesa/main/buffers.c
@@ -532,8 +532,8 @@ _mesa_ReadBuffer(GLenum buffer)
    if (MESA_VERBOSE & VERBOSE_API)
       _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
 
-   if (_mesa_is_user_fbo(fb) && buffer == GL_NONE) {
-      /* This is legal for user-created framebuffer objects */
+   if (buffer == GL_NONE) {
+      /* This is legal--it means that no buffer should be bound for reading. */
       srcBuffer = -1;
    }
    else {