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

[Giulio Camuffo]

this adds a mechanism to mask the views belonging to a layer
to an arbitrary rect, in the global space. The parts that don't fit
in that rect will be clipped away.
---

As per the discussion on IRC, masking layers is preferred to masking views,
so this replaces
http://lists.freedesktop.org/archives/wayland-devel/2013-December/012422.html

 src/compositor.c | 37 ++++++++++++++++++++++++++++++++++++-
 src/compositor.h |  9 +++++++++
 2 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/src/compositor.c b/src/compositor.c
index 8f4bdef..6beea9c 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -1193,10 +1193,14 @@ 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 (ix >= view->layer->mask.x1 && iy >= view->layer->mask.y1 &&
+		    ix <= view->layer->mask.x2 && iy <= view->layer->mask.y2 &&
+		    pixman_region32_contains_point(&view->surface->input,
 						   wl_fixed_to_int(*vx),
 						   wl_fixed_to_int(*vy),
 						   NULL))
@@ -1489,6 +1493,18 @@ view_accumulate_damage(struct weston_view *view,
 	pixman_region32_union(&view->plane->damage,
 			      &view->plane->damage, &damage);
 	pixman_region32_fini(&damage);
+
+	/* set view->clip with the part of view->transform.boundingbox
+	 * that doesn't fit into view->layer->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 be
+	 * in a different layer with a different mask.
+	 */
+	pixman_region32_t mask;
+	pixman_region32_init_with_extents(&mask, &view->layer->mask);
+	pixman_region32_subtract(&view->clip, &view->transform.boundingbox, &mask);
+	pixman_region32_fini(&mask);
+
 	pixman_region32_copy(&view->clip, opaque);
 	pixman_region32_union(opaque, opaque, &view->transform.opaque);
 }
@@ -1652,6 +1668,7 @@ weston_compositor_build_view_list(struct weston_compositor *compositor)
 	wl_list_init(&compositor->view_list);
 	wl_list_for_each(layer, &compositor->layer_list, link) {
 		wl_list_for_each(view, &layer->view_list, layer_link) {
+			view->layer = layer;
 			view_list_add(compositor, view);
 		}
 	}
@@ -1776,11 +1793,29 @@ WL_EXPORT void
 weston_layer_init(struct weston_layer *layer, struct wl_list *below)
 {
 	wl_list_init(&layer->view_list);
+	weston_layer_set_mask_infinite(layer);
 	if (below != NULL)
 		wl_list_insert(below, &layer->link);
 }
 
 WL_EXPORT void
+weston_layer_set_mask(struct weston_layer *layer,
+		      int x, int y, int width, int height)
+{
+	layer->mask.x1 = x;
+	layer->mask.x2 = x + width;
+	layer->mask.y1 = y;
+	layer->mask.y2 = y + height;
+}
+
+WL_EXPORT void
+weston_layer_set_mask_infinite(struct weston_layer *layer)
+{
+	weston_layer_set_mask(layer, INT32_MIN, INT32_MIN,
+				     UINT32_MAX, UINT32_MAX);
+}
+
+WL_EXPORT void
 weston_output_schedule_repaint(struct weston_output *output)
 {
 	struct weston_compositor *compositor = output->compositor;
diff --git a/src/compositor.h b/src/compositor.h
index a161345..ab3de19 100644
--- a/src/compositor.h
+++ b/src/compositor.h
@@ -523,6 +523,7 @@ enum {
 struct weston_layer {
 	struct wl_list view_list;
 	struct wl_list link;
+	pixman_box32_t mask;
 };
 
 struct weston_plane {
@@ -753,6 +754,8 @@ struct weston_view {
 	struct wl_list link;
 	struct wl_list layer_link;
 	struct weston_plane *plane;
+	/* layer is set when building the views list, it's not always valid! */
+	struct weston_layer *layer;
 
 	pixman_region32_t clip;
 	float alpha;                     /* part of geometry, see below */
@@ -980,6 +983,12 @@ void
 weston_layer_init(struct weston_layer *layer, struct wl_list *below);
 
 void
+weston_layer_set_mask(struct weston_layer *layer, int x, int y, int width, int height);
+
+void
+weston_layer_set_mask_infinite(struct weston_layer *layer);
+
+void
 weston_plane_init(struct weston_plane *plane,
 			struct weston_compositor *ec,
 			int32_t x, int32_t y);
-- 
1.8.5.1