Fix sway_session_lock_has_surface

Before this commit, if the cursor is at screen center, and the lock is
swaylock, the cursor would be at swaylock's subsurface(the indicator).

Since it's not the lock surface, `handle_rebase` would refuse to
rebase the cursor to there. Thereby the cursor enter event won't be
sent to swaylock.

This commit fix the issue.

sway/lock.c

@@ -1,6 +1,7 @@
 #include <assert.h>
 #include <wlr/types/wlr_scene.h>
 #include <wlr/types/wlr_session_lock_v1.h>
+#include <wlr/types/wlr_subcompositor.h>
 #include "log.h"
 #include "sway/input/cursor.h"
 #include "sway/input/keyboard.h"
@@ -331,11 +332,26 @@ void sway_session_lock_add_output(struct sway_session_lock *lock,
 	}
 }
 
+static bool wlr_surface_has_subsurface(struct wlr_surface *surface, struct wlr_surface *sub) {
+	struct wlr_subsurface *subsurface = wlr_subsurface_try_from_wlr_surface(sub);
+	if (!subsurface) {
+		return false;
+	}
+	if (!subsurface->parent) {
+		return false;
+	}
+	if (subsurface->parent == surface) {
+		return true;
+	}
+	return wlr_surface_has_subsurface(subsurface->parent, surface);
+}
+
 bool sway_session_lock_has_surface(struct sway_session_lock *lock,
 		struct wlr_surface *surface) {
 	struct sway_session_lock_output *lock_output;
 	wl_list_for_each(lock_output, &lock->outputs, link) {
-		if (lock_output->surface && lock_output->surface->surface == surface) {
+		if (lock_output->surface && (lock_output->surface->surface == surface
+					     || wlr_surface_has_subsurface(lock_output->surface->surface, surface))) {
 			return true;
 		}
 	}