[PATCH weston] compositor: add a layer clipping mechanism

[Giulio Camuffo]

this adds a mechanism to clip the surfaces belonging to a layer
to an arbitrary rect
---

I'm using this functionality in my shell plugin 
(https://github.com/giucam/orbital/tree/workspaces) to implement workspaces.
See http://www.youtube.com/watch?v=_o-sKdyUPO8 for a screencast.
As you see there i need to be able to show all the windows of all the
workspaces, but clipped to their workspace, so they don't stick out over
neighbour ones. So simply showing/hiding layers does not work.

 src/compositor.c | 15 +++++++++++++++
 src/compositor.h |  8 ++++++++
 2 files changed, 23 insertions(+)

diff --git a/src/compositor.c b/src/compositor.c
index 3645b04..a748894 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -1159,6 +1159,7 @@ surface_accumulate_damage(struct weston_surface *surface,
 	pixman_region32_union(&surface->plane->damage,
 			      &surface->plane->damage, &surface->damage);
 	empty_region(&surface->damage);
+	pixman_region32_subtract(opaque, &surface->transform.boundingbox, &surface->layer->clip);
 	pixman_region32_copy(&surface->clip, opaque);
 	pixman_region32_union(opaque, opaque, &surface->transform.opaque);
 }
@@ -1223,6 +1224,7 @@ weston_output_repaint(struct weston_output *output, uint32_t msecs)
 	wl_list_for_each(layer, &ec->layer_list, link) {
 		wl_list_for_each(es, &layer->surface_list, layer_link) {
 			weston_surface_update_transform(es);
+			es->layer = layer;
 			wl_list_insert(ec->surface_list.prev, &es->link);
 			if (es->output == output) {
 				wl_list_insert_list(&frame_callback_list,
@@ -1319,11 +1321,24 @@ WL_EXPORT void
 weston_layer_init(struct weston_layer *layer, struct wl_list *below)
 {
 	wl_list_init(&layer->surface_list);
+	region_init_infinite(&layer->clip);
 	if (below != NULL)
 		wl_list_insert(below, &layer->link);
 }
 
 WL_EXPORT void
+weston_layer_clip(struct weston_layer *layer, int x, int y, int width, int height)
+{
+	pixman_region32_init_rect(&layer->clip, x, y, width, height);
+}
+
+WL_EXPORT void
+weston_layer_clip_infinite(struct weston_layer *layer)
+{
+    region_init_infinite(&layer->clip);
+}
+
+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 1e999a6..b3038bd 100644
--- a/src/compositor.h
+++ b/src/compositor.h
@@ -271,6 +271,7 @@ enum {
 struct weston_layer {
 	struct wl_list surface_list;
 	struct wl_list link;
+	pixman_region32_t clip;
 };
 
 struct weston_plane {
@@ -413,6 +414,7 @@ struct weston_surface {
 	struct wl_list layer_link;
 	float alpha;                     /* part of geometry, see below */
 	struct weston_plane *plane;
+	struct weston_layer *layer;
 
 	void *renderer_state;
 
@@ -598,6 +600,12 @@ void
 weston_layer_init(struct weston_layer *layer, struct wl_list *below);
 
 void
+weston_layer_clip(struct weston_layer *layer, int x, int y, int width, int height);
+
+void
+weston_layer_clip_infinite(struct weston_layer *layer);
+
+void
 weston_plane_init(struct weston_plane *plane, int32_t x, int32_t y);
 void
 weston_plane_release(struct weston_plane *plane);
-- 
1.8.2