[PATCH v18 1/4] compositor-drm: Disallow overlapping overlay planes

[Pekka Paalanen]

On Tue, 10 Jul 2018 14:56:15 +0100
Daniel Stone <daniels at collabora.com> wrote:

> The scanout plane strictly stacks under all overlay planes, and the
> cursor plane above. However, the stacking of overlay planes with respect
> to each other is undefined.
> 
> We can control the stacking order of overlay planes with the zpos
> property, though this significantly complicates plane assignment. In the
> meantime, simply disallow assigning a view to an overlay, when it
> overlaps another view which is already on an overlay. This ensures
> stacking order is irrelevant, since the planes never intersect each
> other.
> 
> Signed-off-by: Daniel Stone <daniels at collabora.com>
> Reported-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> ---
>  libweston/compositor-drm.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/libweston/compositor-drm.c b/libweston/compositor-drm.c
> index 51b2482d9..2305f708f 100644
> --- a/libweston/compositor-drm.c
> +++ b/libweston/compositor-drm.c
> @@ -3324,6 +3324,16 @@ drm_output_propose_state(struct weston_output *output_base,
>  					  &clipped_view);
>  		if (pixman_region32_not_empty(&surface_overlap))
>  			next_plane = primary;
> +
> +		/* We do not control the stacking order of overlay planes;
> +		 * the scanout plane is strictly stacked bottom and the cursor
> +		 * plane top, but the ordering of overlay planes with respect
> +		 * to each other is undefined. Make sure we do not have two
> +		 * planes overlapping each other. */
> +		pixman_region32_intersect(&surface_overlap, &occluded_region,
> +					  &clipped_view);
> +		if (pixman_region32_not_empty(&surface_overlap))
> +			next_plane = primary;
>  		pixman_region32_fini(&surface_overlap);
>  
>  		if (next_plane == NULL)

Reviewed-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>


Thanks,
pq
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