wlr_cursor: handle layout changes

Add the layout `destroy` and `change` events.

When a layout is destroyed, detach is from the wlr_cursor.

When a layout is changed, warp the cursor to the closest layout boundary.

include/wlr/types/wlr_output_layout.h

@@ -9,6 +9,11 @@ struct wlr_output_layout_state;
 struct wlr_output_layout {
 	struct wl_list outputs;
 	struct wlr_output_layout_state *state;
+
+	struct {
+		struct wl_signal change;
+		struct wl_signal destroy;
+	} events;
 };
 
 struct wlr_output_layout_output_state;

types/wlr_cursor.c

@@ -34,11 +34,15 @@ struct wlr_cursor_device {
 };
 
 struct wlr_cursor_state {
+	struct wlr_cursor *cursor;
 	struct wl_list devices;
 	struct wlr_output_layout *layout;
 	struct wlr_xcursor *xcursor;
 	struct wlr_output *mapped_output;
 	struct wlr_box *mapped_box;
+
+	struct wl_listener layout_change;
+	struct wl_listener layout_destroy;
 };
 
 struct wlr_cursor *wlr_cursor_create() {
@@ -55,6 +59,7 @@ struct wlr_cursor *wlr_cursor_create() {
 		return NULL;
 	}
 
+	cur->state->cursor = cur;
 	cur->state->mapped_output = NULL;
 
 	wl_list_init(&cur->state->devices);
@@ -83,7 +88,20 @@ struct wlr_cursor *wlr_cursor_create() {
 	return cur;
 }
 
+static void wlr_cursor_detach_output_layout(struct wlr_cursor *cur) {
+	if (!cur->state->layout) {
+		return;
+	}
+
+	wl_list_remove(&cur->state->layout_destroy.link);
+	wl_list_remove(&cur->state->layout_change.link);
+
+	cur->state->layout = NULL;
+}
+
 void wlr_cursor_destroy(struct wlr_cursor *cur) {
+	wlr_cursor_detach_output_layout(cur);
+
 	struct wlr_cursor_device *device, *device_tmp = NULL;
 	wl_list_for_each_safe(device, device_tmp, &cur->state->devices, link) {
 		wl_list_remove(&device->link);
@@ -430,8 +448,42 @@ void wlr_cursor_detach_input_device(struct wlr_cursor *cur,
 	}
 }
 
+static void handle_layout_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_cursor_state *state =
+		wl_container_of(listener, state, layout_change);
+	wlr_cursor_detach_output_layout(state->cursor);
+}
+
+static void handle_layout_change(struct wl_listener *listener, void *data) {
+	struct wlr_cursor_state *state =
+		wl_container_of(listener, state, layout_change);
+	struct wlr_output_layout *layout = data;
+	if (!wlr_output_layout_contains_point(layout, NULL, state->cursor->x,
+			state->cursor->y)) {
+		// the output we were on has gone away so go to the closest boundary
+		// point
+		double x, y;
+		wlr_output_layout_closest_point(layout, NULL, state->cursor->x,
+			state->cursor->y, &x, &y);
+
+		wlr_cursor_warp_unchecked(state->cursor, x, y);
+	}
+}
+
 void wlr_cursor_attach_output_layout(struct wlr_cursor *cur,
 		struct wlr_output_layout *l) {
+	wlr_cursor_detach_output_layout(cur);
+
+	if (l == NULL) {
+		return;
+	}
+
+	wl_signal_add(&l->events.change, &cur->state->layout_change);
+	cur->state->layout_change.notify = handle_layout_change;
+
+	wl_signal_add(&l->events.destroy, &cur->state->layout_destroy);
+	cur->state->layout_destroy.notify = handle_layout_destroy;
+
 	cur->state->layout = l;
 }
 

types/wlr_output_layout.c

@@ -28,6 +28,10 @@ struct wlr_output_layout *wlr_output_layout_init() {
 	layout->state = calloc(1, sizeof(struct wlr_output_layout_state));
 	layout->state->_box = calloc(1, sizeof(struct wlr_box));
 	wl_list_init(&layout->outputs);
+
+	wl_signal_init(&layout->events.change);
+	wl_signal_init(&layout->events.destroy);
+
 	return layout;
 }
 
@@ -46,6 +50,8 @@ void wlr_output_layout_destroy(struct wlr_output_layout *layout) {
 		return;
 	}
 
+	wl_signal_emit(&layout->events.destroy, layout);
+
 	struct wlr_output_layout_output *_output, *temp = NULL;
 	wl_list_for_each_safe(_output, temp, &layout->outputs, link) {
 		wlr_output_layout_output_destroy(_output);
@@ -69,7 +75,7 @@ static struct wlr_box *wlr_output_layout_output_get_box(
 
 /**
  * This must be called whenever the layout changes to reconfigure the auto
- * configured outputs.
+ * configured outputs and emit the `changed` event.
  *
  * Auto configured outputs are placed to the right of the north east corner of
  * the rightmost output in the layout in a horizontal line.
@@ -108,6 +114,8 @@ static void wlr_output_layout_reconfigure(struct wlr_output_layout *layout) {
 		l_output->y = max_x_y;
 		max_x += box->width;
 	}
+
+	wl_signal_emit(&layout->events.change, layout);
 }
 
 static void handle_output_resolution(struct wl_listener *listener, void *data) {