diff --git a/config/config.py b/config/config.py
index e944484..e60cbdc 100644
--- a/config/config.py
+++ b/config/config.py
@@ -654,6 +654,7 @@ def OnKeyRelease(self, keyId):
 			self.shiftFocus = None;
 
 	def OnTimer(self):
+		#NOTE: OnTimer() calls currently disabled.
 		battery = psutil.sensors_battery();
 		try:
 			if not battery.power_plugged:
@@ -677,7 +678,9 @@ def OnTimer(self):
 			self.batteryAlarmLevel = 0;
 
 class Compositor(chamfer.Compositor):
-	pass
+	def OnRedirectExternal(self, title, className):
+		#Used only in standalone compositor mode. Return False to filter out incompatible WM/UI components.
+		return True;
 
 backend = Backend();
 chamfer.BindBackend(backend);
diff --git a/src/backend.cpp b/src/backend.cpp
index ad0a725..5335a6d 100644
--- a/src/backend.cpp
+++ b/src/backend.cpp
@@ -1359,7 +1359,13 @@ sint Default::HandleEvent(bool forcePoll){
 				if(!standaloneComp){
 					const WManager::Container *proot = pclient->pcontainer->GetRoot();
 					StackClients(proot);
-				}else{
+
+					netClientList.clear();
+					for(auto &p : clients)
+						netClientList.push_back(p.first->window);
+					xcb_change_property(pcon,XCB_PROP_MODE_REPLACE,pscr->root,ewmh._NET_CLIENT_LIST,XCB_ATOM_WINDOW,32,netClientList.size(),netClientList.data());
+				}else
+				if(ApproveExternal(&wmName,&wmClass)){
 					//clientStack won't get cleared in standalone compositor mode
 					if(std::get<2>(*mrect) != 0){ //!= XCB_NONE
 						auto m = std::find_if(clientStack.begin(),clientStack.end(),[&](auto &p)->bool{
@@ -1367,11 +1373,6 @@ sint Default::HandleEvent(bool forcePoll){
 						});
 						clientStack.insert(m+1,pclient);
 					}else clientStack.push_front(pclient);
-
-					netClientList.clear();
-					for(auto &p : clients)
-						netClientList.push_back(p.first->window);
-					xcb_change_property(pcon,XCB_PROP_MODE_REPLACE,pscr->root,ewmh._NET_CLIENT_LIST,XCB_ATOM_WINDOW,32,netClientList.size(),netClientList.data());
 				}
 			}
 
diff --git a/src/backend.h b/src/backend.h
index 2136d63..dc67083 100644
--- a/src/backend.h
+++ b/src/backend.h
@@ -178,6 +178,7 @@ friend class Compositor::TexturePixmap;
 	};
 	virtual X11Client * FindClient(xcb_window_t, MODE) const = 0;
 	virtual void TimerEvent() = 0;
+	virtual bool ApproveExternal(const BackendStringProperty *, const BackendStringProperty *) = 0;
 	//void * GetProperty(xcb_atom_t, xcb_atom_t) const;
 	//void FreeProperty(...) const;
 protected:
diff --git a/src/config.cpp b/src/config.cpp
index e8cbca6..6da4221 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -707,6 +707,10 @@ CompositorInterface::~CompositorInterface(){
 	//
 }
 
+bool CompositorInterface::OnRedirectExternal(std::string title, std::string className){
+	return true;
+}
+
 void CompositorInterface::Bind(boost::python::object obj){
 	CompositorInterface &compositorInt = boost::python::extract<CompositorInterface&>(obj)();
 	pcompositorInt = &compositorInt;
@@ -724,6 +728,21 @@ CompositorProxy::~CompositorProxy(){
 	//
 }
 
+bool CompositorProxy::OnRedirectExternal(std::string title, std::string className){
+	boost::python::override ovr = this->get_override("OnRedirectExternal");
+	if(ovr){
+		try{
+			return ovr(title,className);
+		}catch(boost::python::error_already_set &){
+			PyErr_Print();
+			//
+			boost::python::handle_exception();
+			PyErr_Clear();
+		}
+	}
+	return CompositorInterface::OnRedirectExternal(title,className);
+}
+
 CompositorConfig::CompositorConfig(CompositorInterface *_pcompositorInt) : pcompositorInt(_pcompositorInt){
 	pcompositorInt->pcompositor = this;
 }
@@ -1126,6 +1145,7 @@ BOOST_PYTHON_MODULE(chamfer){
 		.value("USER_BIT",Compositor::ClientFrame::SHADER_FLAG_USER_BIT);
 	
 	boost::python::class_<CompositorProxy,boost::noncopyable>("Compositor")
+		.def("OnRedirectExternal",&CompositorInterface::OnRedirectExternal)
 		.def_readwrite("deviceIndex",&CompositorInterface::deviceIndex)
 		.def_readwrite("debugLayers",&CompositorInterface::debugLayers)
 		.def_readwrite("scissoring",&CompositorInterface::scissoring)
diff --git a/src/config.h b/src/config.h
index 438e185..0a2a3e7 100644
--- a/src/config.h
+++ b/src/config.h
@@ -179,7 +179,8 @@ class BackendConfig{
 class CompositorInterface{
 public:
 	CompositorInterface();
-	~CompositorInterface();
+	virtual ~CompositorInterface();
+	virtual bool OnRedirectExternal(std::string, std::string);
 
 	sint deviceIndex;
 	bool debugLayers;
@@ -204,6 +205,7 @@ class CompositorProxy : public CompositorInterface, public boost::python::wrappe
 public:
 	CompositorProxy();
 	~CompositorProxy();
+	bool OnRedirectExternal(std::string, std::string);
 };
 
 class CompositorConfig{
diff --git a/src/main.cpp b/src/main.cpp
index 99ab3d8..295a85b 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -665,6 +665,10 @@ class DefaultBackend : public Backend::Default, public RunBackend{
 		//
 		Config::BackendInterface::pbackendInt->OnTimer();
 	}
+
+	bool ApproveExternal(const Backend::BackendStringProperty *pwmName, const Backend::BackendStringProperty *pwmClass){
+		return Config::CompositorInterface::pcompositorInt->OnRedirectExternal(pwmName->pstr,pwmClass->pstr);
+	}
 };
 
 //TODO: some of these functions can be templated and shared with the DefaultBackend
@@ -785,6 +789,10 @@ class DebugBackend : public Backend::Debug, public RunBackend{
 	void TimerEvent(){
 		//
 	}
+
+	bool ApproveExternal(const Backend::BackendStringProperty *pwmName, const Backend::BackendStringProperty *pwmClass){
+		return true;
+	}
 };
 
 class DefaultCompositor : public Compositor::X11Compositor, public RunCompositor{