feat: on frame listener

include/window.h

@@ -3,6 +3,7 @@
 #define H_WINDOW_
 
 #include <cstddef>
+#include <functional>
 
 #include <EGL/egl.h>
 #include <EGL/eglext.h>
@@ -10,6 +11,8 @@
 
 #define UNUSED(x) (void)(x)
 
+typedef std::function<void()> IFrameListener;
+
 class WindowImpl {
 public:
 	WindowImpl() = default;
@@ -19,6 +22,7 @@ public:
 	WindowImpl(WindowImpl&&) = delete;
 protected:
 	virtual bool Dispatch() = 0;
+	virtual void OnFrame(IFrameListener fn) = 0;
 
 	virtual size_t GetWidth() const = 0;
 	virtual size_t GetHeight() const = 0;
@@ -39,6 +43,10 @@ public:
 	size_t GetWidth() const;
 	size_t GetHeight() const;
 
+public:
+  void Run();
+	void OnFrame(IFrameListener fn);
+
 private:
 	WindowImpl* m_impl;