[PATCH v16 05/23] compositor-drm: Fully account for buffer transformation

[Pekka Paalanen]

On Thu,  5 Jul 2018 18:16:32 +0100
Daniel Stone <daniels at collabora.com> wrote:

> In our new and improved helper to determine the src/dest values for a
> buffer on a given plane, make sure we account for all buffer
> transformations, including viewport clipping.
> 
> Rather than badly open-coding it ourselves, just use the helper which
> does exactly this.
> 
> Signed-off-by: Daniel Stone <daniels at collabora.com>
> Reported-by: Tiago Gomes <tiago.gomes at codethink.co.uk>
> Tested-by: Emre Ucan <eucan at de.adit-jv.com>
> ---
>  libweston/compositor-drm.c | 60 +++++++++++++-------------------------
>  1 file changed, 20 insertions(+), 40 deletions(-)
> 
> diff --git a/libweston/compositor-drm.c b/libweston/compositor-drm.c
> index 03ff031d9..59e5e4ec6 100644
> --- a/libweston/compositor-drm.c
> +++ b/libweston/compositor-drm.c
> @@ -1181,10 +1181,10 @@ drm_plane_state_coords_for_view(struct drm_plane_state *state,
>  				struct weston_view *ev)
>  {
>  	struct drm_output *output = state->output;
> -	struct weston_buffer_viewport *viewport = &ev->surface->buffer_viewport;
> +	struct weston_buffer *buffer = ev->surface->buffer_ref.buffer;
>  	pixman_region32_t dest_rect, src_rect;
>  	pixman_box32_t *box, tbox;
> -	wl_fixed_t sx1, sy1, sx2, sy2;
> +	float sxf1, syf1, sxf2, syf2;
>  
>  	/* Update the base weston_plane co-ordinates. */
>  	box = pixman_region32_extents(&ev->transform.boundingbox);
> @@ -1216,51 +1216,31 @@ drm_plane_state_coords_for_view(struct drm_plane_state *state,
>  	pixman_region32_intersect(&src_rect, &ev->transform.boundingbox,
>  				  &output->base.region);
>  	box = pixman_region32_extents(&src_rect);
> +	weston_view_from_global_float(ev, box->x1, box->y1, &sxf1, &syf1);
> +	weston_surface_to_buffer_float(ev->surface, sxf1, syf1, &sxf1, &syf1);
> +	weston_view_from_global_float(ev, box->x2, box->y2, &sxf2, &syf2);
> +	weston_surface_to_buffer_float(ev->surface, sxf2, syf2, &sxf2, &syf2);
> +	pixman_region32_fini(&src_rect);


You forgot the checks that weston_transformed_rect() does to ensure
the resulting rectangle is legal (x1 <= x2, y1 <= y2).

Therefore I believe this may break if buffer transform is not identity.

>  
> -	/* Accounting for any transformations made to this particular surface
> -	 * view, find the source rectangle to use. */
> -	weston_view_from_global_fixed(ev,
> -				      wl_fixed_from_int(box->x1),
> -				      wl_fixed_from_int(box->y1),
> -				      &sx1, &sy1);
> -	weston_view_from_global_fixed(ev,
> -				      wl_fixed_from_int(box->x2),
> -				      wl_fixed_from_int(box->y2),
> -				      &sx2, &sy2);
> +	/* Shift from S23.8 wl_fixed to U16.16 KMS fixed-point encoding. */

src_x, srx_y are signed, src_w, src_h are unsigned

> +	state->src_x = wl_fixed_from_double(sxf1) << 8;
> +	state->src_y = wl_fixed_from_double(syf1) << 8;
> +	state->src_w = wl_fixed_from_double(sxf2 - sxf1) << 8;
> +	state->src_h = wl_fixed_from_double(syf2 - syf1) << 8;

The above may cause the subtraction here to become negative.

Is using wl_fixed_from_double() easier to read than

	state->src_x = round(sxf1 * 65536.0);

Not sure we'd even need round().

Otherwise looks good to me.


Thanks,
pq

>  
>  	/* Clamp our source co-ordinates to surface bounds; it's possible
>  	 * for intermediate translations to give us slightly incorrect
>  	 * co-ordinates if we have, for example, multiple zooming
>  	 * transformations. View bounding boxes are also explicitly rounded
>  	 * greedily. */
> -	if (sx1 < 0)
> -		sx1 = 0;
> -	if (sy1 < 0)
> -		sy1 = 0;
> -	if (sx2 > wl_fixed_from_int(ev->surface->width))
> -		sx2 = wl_fixed_from_int(ev->surface->width);
> -	if (sy2 > wl_fixed_from_int(ev->surface->height))
> -		sy2 = wl_fixed_from_int(ev->surface->height);
> -
> -	tbox.x1 = sx1;
> -	tbox.y1 = sy1;
> -	tbox.x2 = sx2;
> -	tbox.y2 = sy2;
> -	pixman_region32_fini(&src_rect);
> -
> -	/* Apply viewport transforms in reverse, to get the source co-ordinates
> -	 * in buffer space. */
> -	tbox = weston_transformed_rect(wl_fixed_from_int(ev->surface->width),
> -				       wl_fixed_from_int(ev->surface->height),
> -				       viewport->buffer.transform,
> -				       viewport->buffer.scale,
> -				       tbox);
> -
> -	/* Shift from S23.8 wl_fixed to U16.16 KMS fixed-point encoding. */
> -	state->src_x = tbox.x1 << 8;
> -	state->src_y = tbox.y1 << 8;
> -	state->src_w = (tbox.x2 - tbox.x1) << 8;
> -	state->src_h = (tbox.y2 - tbox.y1) << 8;
> +	if (state->src_x < 0)
> +		state->src_x = 0;
> +	if (state->src_y < 0)
> +		state->src_y = 0;
> +	if (state->src_w > (uint32_t) ((buffer->width << 16) - state->src_x))
> +		state->src_w = (buffer->width << 16) - state->src_x;
> +	if (state->src_h > (uint32_t) ((buffer->height << 16) - state->src_y))
> +		state->src_h = (buffer->height << 16) - state->src_y;
>  }
>  
>  /**

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