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mesa: Handle GL_BACK correctly for ES 3.0 in glDrawBuffers(). 

In ES 3.0, when calling glDrawBuffers() on the window system
framebuffer, the only valid targets are GL_NONE or GL_BACK.  Since there
is no stereo rendering in ES 3.0, this is a single buffer, unlike
desktop where it may be two (and thus isn't allowed).

For single-buffered configs, GL_BACK ironically means the front (and
only) buffer.  I'm not sure that it matters, however, as ES shouldn't
have front buffer rendering in the first place.

Fixes es3conform framebuffer_blit_coverage_default_draw_buffer_binding.

v2: Update GLES3 spec reference.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com> [v2]
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> [v1]
This commit is contained in:
Kenneth Graunke 2012-12-18 13:26:03 -08:00 committed by Ian Romanick
parent d786bf2c2a
commit fd3891cbbe
1 changed files with 19 additions and 4 deletions
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23
src/mesa/main/buffers.c
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@ -94,7 +94,7 @@ supported_buffer_bitmask(const struct gl_context *ctx,
* GL_FRONT_AND_BACK), return the corresponding bitmask of BUFFER_BIT_* flags.
*/
static GLbitfield
draw_buffer_enum_to_bitmask(GLenum buffer)
draw_buffer_enum_to_bitmask(const struct gl_context *ctx, GLenum buffer)
{
switch (buffer) {
case GL_NONE:
@ -102,6 +102,21 @@ draw_buffer_enum_to_bitmask(GLenum buffer)
case GL_FRONT:
return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_FRONT_RIGHT;
case GL_BACK:
if (_mesa_is_gles3(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.
*/
if (ctx->DrawBuffer->Visual.doubleBufferMode)
return BUFFER_BIT_BACK_LEFT;
return BUFFER_BIT_FRONT_LEFT;
}
return BUFFER_BIT_BACK_LEFT | BUFFER_BIT_BACK_RIGHT;
case GL_RIGHT:
return BUFFER_BIT_FRONT_RIGHT | BUFFER_BIT_BACK_RIGHT;
@ -241,7 +256,7 @@ _mesa_DrawBuffer(GLenum buffer)
else {
const GLbitfield supportedMask
= supported_buffer_bitmask(ctx, ctx->DrawBuffer);
destMask = draw_buffer_enum_to_bitmask(buffer);
destMask = draw_buffer_enum_to_bitmask(ctx, buffer);
if (destMask == BAD_MASK) {
/* totally bogus buffer */
_mesa_error(ctx, GL_INVALID_ENUM,
@ -321,7 +336,7 @@ _mesa_DrawBuffers(GLsizei n, const GLenum *buffers)
return;
}
destMask[output] = draw_buffer_enum_to_bitmask(buffers[output]);
destMask[output] = draw_buffer_enum_to_bitmask(ctx, buffers[output]);
/* From the OpenGL 3.0 specification, page 258:
* "Each buffer listed in bufs must be one of the values from tables
@ -451,7 +466,7 @@ _mesa_drawbuffers(struct gl_context *ctx, GLuint n, const GLenum *buffers,
const GLbitfield supportedMask = supported_buffer_bitmask(ctx, fb);
GLuint output;
for (output = 0; output < n; output++) {
mask[output] = draw_buffer_enum_to_bitmask(buffers[output]);
mask[output] = draw_buffer_enum_to_bitmask(ctx, buffers[output]);
ASSERT(mask[output] != BAD_MASK);
mask[output] &= supportedMask;
}