Add Tree::wakeUpSignal() getter

include/behaviortree_cpp/bt_factory.h

@@ -137,6 +137,14 @@ class Tree
    */
   void emitWakeUpSignal();
 
+  /**
+   * @brief Returns the shared WakeUpSignal used by this tree.
+   * This can be used to check for preemption externally, e.g. when
+   * implementing custom sleep logic with a different clock source.
+   * Returns nullptr if the tree has not been initialized yet.
+   */
+  [[nodiscard]] std::shared_ptr<WakeUpSignal> wakeUpSignal() const;
+
   ~Tree();
 
   /// Tick the root of the tree once, even if a node invoked

src/bt_factory.cpp

@@ -664,6 +664,11 @@ void Tree::emitWakeUpSignal()
   wake_up_->emitSignal();
 }
 
+std::shared_ptr<WakeUpSignal> Tree::wakeUpSignal() const
+{
+  return wake_up_;
+}
+
 Tree::~Tree()
 {
   haltTree();