implement simple stroke undo based on actions history

engine/action.h

@@ -0,0 +1,24 @@
+#pragma once
+
+class Action
+{
+public:
+    virtual void run() = 0;
+    virtual void undo() = 0;
+};
+
+class ActionManager
+{
+public:
+    static ActionManager I;
+    std::stack<std::unique_ptr<Action>> m_actions;
+    static void add(Action* action)
+    {
+        I.m_actions.emplace(action);
+    }
+    static void undo()
+    {
+        I.m_actions.top()->undo();
+        I.m_actions.pop();
+    }
+};