[PATCH weston] compositor: add a masking mechanism to weston_view

[Giulio Camuffo]

This adds a 'mask' pixman_region32 to weston_view and to weston_view::geometry.
A user, a shell probably, can set a view's mask to some region (e.g. the
workspace area) and the view, and all its transform children, will be
clipped to that region.
weston_view::geometry.mask is the intersection of the view's mask and
of the parent's geometry.mask.
---
 src/compositor.c | 25 +++++++++++++++++++++++--
 src/compositor.h |  2 ++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/compositor.c b/src/compositor.c
index 32e72b1..8316653 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -366,6 +366,8 @@ weston_view_create(struct weston_surface *surface)
 	view->plane = NULL;
 
 	pixman_region32_init(&view->clip);
+	region_init_infinite(&view->mask);
+	pixman_region32_init(&view->geometry.mask);
 
 	view->alpha = 1.0;
 	pixman_region32_init(&view->transform.opaque);
@@ -926,6 +928,11 @@ weston_view_update_transform(struct weston_view *view)
 
 	weston_view_damage_below(view);
 
+	if (parent)
+		pixman_region32_intersect(&view->geometry.mask, &view->mask, &parent->geometry.mask);
+	else
+		pixman_region32_copy(&view->geometry.mask, &view->mask);
+
 	pixman_region32_fini(&view->transform.boundingbox);
 	pixman_region32_fini(&view->transform.opaque);
 	pixman_region32_init(&view->transform.opaque);
@@ -1185,10 +1192,14 @@ weston_compositor_pick_view(struct weston_compositor *compositor,
 			    wl_fixed_t *vx, wl_fixed_t *vy)
 {
 	struct weston_view *view;
+	int ix = wl_fixed_to_int(x);
+	int iy = wl_fixed_to_int(y);
 
 	wl_list_for_each(view, &compositor->view_list, link) {
 		weston_view_from_global_fixed(view, x, y, vx, vy);
-		if (pixman_region32_contains_point(&view->surface->input,
+		if (pixman_region32_contains_point(&view->geometry.mask,
+						   ix, iy, NULL) &&
+		    pixman_region32_contains_point(&view->surface->input,
 						   wl_fixed_to_int(*vx),
 						   wl_fixed_to_int(*vy),
 						   NULL))
@@ -1274,8 +1285,10 @@ weston_view_destroy(struct weston_view *view)
 	wl_list_remove(&view->link);
 	wl_list_remove(&view->layer_link);
 
+	pixman_region32_fini(&view->mask);
 	pixman_region32_fini(&view->clip);
 	pixman_region32_fini(&view->transform.boundingbox);
+	pixman_region32_fini(&view->geometry.mask);
 
 	weston_view_set_transform_parent(view, NULL);
 
@@ -1481,7 +1494,15 @@ view_accumulate_damage(struct weston_view *view,
 	pixman_region32_union(&view->plane->damage,
 			      &view->plane->damage, &damage);
 	pixman_region32_fini(&damage);
-	pixman_region32_copy(&view->clip, opaque);
+
+	/* set view->clip with the part of view->transform.boundingbox
+	 * that doesn't fit into view->geometry.mask, then add the opaque region
+	 * to it. We don't do the opposite, adding view->clip to opaque,
+	 * because opaque is then passed to the next views, which may have
+	 * a different mask.
+	 */
+	pixman_region32_subtract(&view->clip, &view->transform.boundingbox, &view->geometry.mask);
+	pixman_region32_union(&view->clip, &view->clip, opaque);
 	pixman_region32_union(opaque, opaque, &view->transform.opaque);
 }
 
diff --git a/src/compositor.h b/src/compositor.h
index 3e878c8..e0b3895 100644
--- a/src/compositor.h
+++ b/src/compositor.h
@@ -750,6 +750,7 @@ struct weston_view {
 	struct wl_list layer_link;
 	struct weston_plane *plane;
 
+	pixman_region32_t mask;
 	pixman_region32_t clip;
 	float alpha;                     /* part of geometry, see below */
 
@@ -762,6 +763,7 @@ struct weston_view {
 	struct {
 		float x, y; /* surface translation on display */
 		int32_t width, height;
+		pixman_region32_t mask;
 
 		/* struct weston_transform */
 		struct wl_list transformation_list;
-- 
1.8.4.2