pixman-renderer, gl-renderer: Destroy surface state with the renderer

Previously the renderers destroy function assumed they are only called
when the compositor is shutting down and that the compositor had
already destroyed all the surfaces. However, if a runtime renderer
switch would be done, the surface state would be leaked.

This patch adds a destroy_signal to the pixman and gl renderers. The
surface state objects will listen for that signal and destroy
themselves if needed.

This is a step towards runtime switchable renderers.
diff --git a/src/pixman-renderer.c b/src/pixman-renderer.c
index 98a910c..79c1d5b 100644
--- a/src/pixman-renderer.c
+++ b/src/pixman-renderer.c
@@ -43,6 +43,7 @@
 	struct weston_buffer_reference buffer_ref;
 
 	struct wl_listener surface_destroy_listener;
+	struct wl_listener renderer_destroy_listener;
 };
 
 struct pixman_renderer {
@@ -51,6 +52,8 @@
 	int repaint_debug;
 	pixman_image_t *debug_color;
 	struct weston_binding *debug_binding;
+
+	struct wl_signal destroy_signal;
 };
 
 static inline struct pixman_output_state *
@@ -593,12 +596,11 @@
 }
 
 static void
-surface_state_handle_surface_destroy(struct wl_listener *listener, void *data)
+pixman_renderer_surface_state_destroy(struct pixman_surface_state *ps)
 {
-	struct pixman_surface_state *ps;
+	wl_list_remove(&ps->surface_destroy_listener.link);
+	wl_list_remove(&ps->renderer_destroy_listener.link);
 
-	ps = container_of(listener, struct pixman_surface_state,
-			  surface_destroy_listener);
 
 	ps->surface->renderer_state = NULL;
 
@@ -610,10 +612,33 @@
 	free(ps);
 }
 
+static void
+surface_state_handle_surface_destroy(struct wl_listener *listener, void *data)
+{
+	struct pixman_surface_state *ps;
+
+	ps = container_of(listener, struct pixman_surface_state,
+			  surface_destroy_listener);
+
+	pixman_renderer_surface_state_destroy(ps);
+}
+
+static void
+surface_state_handle_renderer_destroy(struct wl_listener *listener, void *data)
+{
+	struct pixman_surface_state *ps;
+
+	ps = container_of(listener, struct pixman_surface_state,
+			  renderer_destroy_listener);
+
+	pixman_renderer_surface_state_destroy(ps);
+}
+
 static int
 pixman_renderer_create_surface(struct weston_surface *surface)
 {
 	struct pixman_surface_state *ps;
+	struct pixman_renderer *pr = get_renderer(surface->compositor);
 
 	ps = calloc(1, sizeof *ps);
 	if (!ps)
@@ -628,6 +653,11 @@
 	wl_signal_add(&surface->destroy_signal,
 		      &ps->surface_destroy_listener);
 
+	ps->renderer_destroy_listener.notify =
+		surface_state_handle_renderer_destroy;
+	wl_signal_add(&pr->destroy_signal,
+		      &ps->renderer_destroy_listener);
+
 	return 0;
 }
 
@@ -656,6 +686,7 @@
 {
 	struct pixman_renderer *pr = get_renderer(ec);
 
+	wl_signal_emit(&pr->destroy_signal, pr);
 	weston_binding_destroy(pr->debug_binding);
 	free(pr);
 
@@ -710,6 +741,8 @@
 
 	wl_display_add_shm_format(ec->wl_display, WL_SHM_FORMAT_RGB565);
 
+	wl_signal_init(&renderer->destroy_signal);
+
 	return 0;
 }