On Wed, Sep 5, 2012 at 4:22 PM, Paul Berry <stereotype...@gmail.com> wrote:
> From the GL 4.3 spec, section 18.3.1 "Blitting Pixel Rectangles":
>
> If SAMPLE_BUFFERS for either the read framebuffer or draw
> framebuffer is greater than zero, no copy is performed and an
> INVALID_OPERATION error is generated if the dimensions of the
> source and destination rectangles provided to BlitFramebuffer are
> not identical, or if the formats of the read and draw framebuffers
> are not identical.
>
> It is not clear from the spec whether "dimensions" should mean both
> sign and magnitude, or just magnitude.
>
> Previously, Mesa interpreted "dimensions" as meaning both sign and
> magnitude, so any multisampled blit that attempted to flip the image
> in the X and/or Y direction would fail.
>
> However, Y flips are likely to be commonplace in OpenGL applications
> that have been ported from DirectX applications, as a result of the
> fact that DirectX and OpenGL differ in their orientation of the Y
> axis. Furthermore, at least one commercial driver (nVidia) permits Y
> filps, and L4D2 relies on them being permitted. So it seems prudent
> for Mesa to permit them.
>
> This patch changes Mesa to allow both X and Y flips, since there is no
> language in the spec to indicate that X and Y flips should be treated
> differently.
>
> NOTE: This is a candidate for stable release branches.
> ---
> src/mesa/main/fbobject.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/main/fbobject.c b/src/mesa/main/fbobject.c
> index 59a5ec3..abc9d83 100644
> --- a/src/mesa/main/fbobject.c
> +++ b/src/mesa/main/fbobject.c
> @@ -2979,8 +2979,8 @@ _mesa_BlitFramebufferEXT(GLint srcX0, GLint srcY0,
> GLint srcX1, GLint srcY1,
> /* extra checks for multisample copies... */
> if (readFb->Visual.samples > 0 || drawFb->Visual.samples > 0) {
> /* src and dest region sizes must be the same */
> - if (srcX1 - srcX0 != dstX1 - dstX0 ||
> - srcY1 - srcY0 != dstY1 - dstY0) {
> + if (abs(srcX1 - srcX0) != abs(dstX1 - dstX0) ||
> + abs(srcY1 - srcY0) != abs(dstY1 - dstY0)) {
> _mesa_error(ctx, GL_INVALID_OPERATION,
> "glBlitFramebufferEXT(bad src/dst multisample region
> sizes)");
> return;
> --
> 1.7.7.6
>
> _______________________________________________
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> mesa-dev@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
Reviewed-by: Anuj Phogat <anuj.pho...@gmail.com>
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