core: 添加窗口所属层级判定

src/core/policy.c

@@ -0,0 +1,10 @@
+#include "core/policy.h"
+
+#include "base/macros.h"
+#include "core/state.h"
+
+layer_type_t policy_adjust_window_layer_from_transient(
+  const state_t *state, window_id_t transient_for, layer_type_t base_layer) {
+  const window_t *window = state_window_get(state, transient_for);
+  return MAX(window->layer, base_layer);
+}