[Mesa-dev] [PATCH 1/6] anv: Set viewport extents correctly when height is negative

[Iago Toral]

On Mon, 2017-01-23 at 14:12 -0800, Jason Ekstrand wrote:
> As per VK_KHR_maintenance1, setting a negative height in the viewport
> can be used to get flipped coordinates.  This is, aparently, very
> useful
> when porting D3D apps to Vulkan.  All we need to do to support this
> is
> to make sure we actually set the min and max correctly.
> ---
>  src/intel/vulkan/gen8_cmd_buffer.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/intel/vulkan/gen8_cmd_buffer.c
> b/src/intel/vulkan/gen8_cmd_buffer.c
> index f22037b..ab68872 100644
> --- a/src/intel/vulkan/gen8_cmd_buffer.c
> +++ b/src/intel/vulkan/gen8_cmd_buffer.c
> @@ -59,8 +59,8 @@ gen8_cmd_buffer_emit_viewport(struct anv_cmd_buffer
> *cmd_buffer)
>           .YMaxClipGuardband = 1.0f,
>           .XMinViewPort = vp->x,
>           .XMaxViewPort = vp->x + vp->width - 1,
> -         .YMinViewPort = vp->y,
> -         .YMaxViewPort = vp->y + vp->height - 1,
> +         .YMinViewPort = MIN2(vp->y, vp->y + vp->height),
> +         .YMaxViewPort = MAX2(vp->y, vp->y + vp->height) - 1,
>        };

If we have y = 0 and height = -100, shouldn't we use YMinVP = -99 and
YMaxVP = 0 instead of (-100, -1)?

>        GENX(SF_CLIP_VIEWPORT_pack)(NULL, sf_clip_state.map + i * 64,