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mesa: fix pbuffers because internally they are front buffers

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This fixes the egl_ext_device_base piglit test, which uses EGL pbuffers.

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
This commit is contained in:
Marek Olšák 2019-04-26 20:53:52 -04:00
parent f753f913f5
commit 35294f2eca
1 changed files with 36 additions and 20 deletions
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56
src/mesa/main/buffers.c
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@ -93,32 +93,48 @@ supported_buffer_bitmask(const struct gl_context *ctx,
static GLbitfield
draw_buffer_enum_to_bitmask(const struct gl_context *ctx, GLenum buffer)
{
/* If the front buffer is the only buffer, GL_BACK and all other flags
* that include BACK select the front buffer for drawing. There are
* several reasons we want to do this.
*
* 1) OpenGL ES 3.0 requires it:
*
* 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."
*
* 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.
*
* 2) Pbuffers are back buffers from the application point of view,
* but they are front buffers from the Mesa point of view,
* because they are always single buffered.
*/
if (!ctx->DrawBuffer->Visual.doubleBufferMode) {
switch (buffer) {
case GL_BACK:
buffer = GL_FRONT;
break;
case GL_BACK_RIGHT:
buffer = GL_FRONT_RIGHT;
break;
case GL_BACK_LEFT:
buffer = GL_FRONT_LEFT;
break;
}
}
switch (buffer) {
case GL_NONE:
return 0;
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;
case GL_RIGHT:
return BUFFER_BIT_FRONT_RIGHT | BUFFER_BIT_BACK_RIGHT;