touch-calibration: Clean-up if touch calibrator has been enabled

Seems that we're still missing layer clean-ups, with the touch
calibrator being one of them. Call the appropriate function when
shutting down the compositor instance.

Fixes: #603

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

libweston/compositor.c

@@ -7852,6 +7852,9 @@ weston_compositor_shutdown(struct weston_compositor *ec)
 	wl_event_source_remove(ec->idle_source);
 	wl_event_source_remove(ec->repaint_timer);
 
+	if (ec->touch_calibration)
+		weston_compositor_destroy_touch_calibrator(ec);
+
 	/* Destroy all outputs associated with this compositor */
 	wl_list_for_each_safe(output, next, &ec->output_list, link)
 		output->destroy(output);

libweston/libweston-internal.h

@@ -389,6 +389,8 @@ const uint64_t *
 weston_drm_format_get_modifiers(const struct weston_drm_format *format,
 				unsigned int *count_out);
 
+void
+weston_compositor_destroy_touch_calibrator(struct weston_compositor *compositor);
 /**
  * paint node
  *

libweston/touch-calibration.c

@@ -674,6 +674,16 @@ bind_touch_calibration(struct wl_client *client,
 	}
 }
 
+void
+weston_compositor_destroy_touch_calibrator(struct weston_compositor *ec)
+{
+	/* TODO: handle weston_compositor::touch_calibrator destruction
+	 * see
+	 * https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/819#note_1345191
+	 */
+	weston_layer_fini(&ec->calibrator_layer);
+}
+
 /** Advertise touch_calibration support
  *
  * \param compositor The compositor to init for.