Do not crash when a monitor is removed

include/modules/hyprland/backend.hpp

@@ -1,5 +1,5 @@
 #pragma once
-#include <deque>
+#include <list>
 #include <functional>
 #include <memory>
 #include <mutex>
@@ -7,11 +7,19 @@
 #include <thread>
 
 namespace waybar::modules::hyprland {
+
+class EventHandler {
+public:
+  virtual void onEvent(const std::string& ev) = 0;
+  virtual ~EventHandler() = default;
+};
+
 class IPC {
  public:
   IPC() { startIPC(); }
 
-  void registerForIPC(const std::string&, std::function<void(const std::string&)>);
+  void registerForIPC(const std::string&, EventHandler*);
+  void unregisterForIPC(EventHandler*);
 
   std::string getSocket1Reply(const std::string& rq);
 
@@ -20,7 +28,7 @@ class IPC {
   void parseIPC(const std::string&);
 
   std::mutex callbackMutex;
-  std::deque<std::pair<std::string, std::function<void(const std::string&)>>> callbacks;
+  std::list<std::pair<std::string, EventHandler*>> callbacks;
 };
 
 inline std::unique_ptr<IPC> gIPC;

include/modules/hyprland/language.hpp

@@ -7,10 +7,11 @@
 
 namespace waybar::modules::hyprland {
 
-class Language : public waybar::AButton {
+class Language : public waybar::AButton,
+public EventHandler {
  public:
   Language(const std::string&, const waybar::Bar&, const Json::Value&);
-  ~Language() = default;
+  ~Language();
 
   auto update() -> void;
 

include/modules/hyprland/window.hpp

@@ -9,10 +9,11 @@
 
 namespace waybar::modules::hyprland {
 
-class Window : public waybar::ALabel {
+class Window : public waybar::ALabel,
+ public EventHandler {
  public:
   Window(const std::string&, const waybar::Bar&, const Json::Value&);
-  ~Window() = default;
+  ~Window();
 
   auto update() -> void;
 

src/modules/hyprland/backend.cpp

@@ -95,15 +95,37 @@ void IPC::parseIPC(const std::string& ev) {
 
   for (auto& [eventname, handler] : callbacks) {
     if (eventname == request) {
-      handler(ev);
+      handler->onEvent(ev);
     }
   }
 }
 
-void IPC::registerForIPC(const std::string& ev, std::function<void(const std::string&)> fn) {
+void IPC::registerForIPC(const std::string& ev, EventHandler* ev_handler) {
+  if (!ev_handler) {
+    return;
+  }
   callbackMutex.lock();
 
-  callbacks.emplace_back(std::make_pair(ev, fn));
+  callbacks.emplace_back(std::make_pair(ev, ev_handler));
+
+  callbackMutex.unlock();
+}
+
+void IPC::unregisterForIPC(EventHandler* ev_handler) {
+    if (!ev_handler) {
+    return;
+  }
+
+  callbackMutex.lock();
+
+  for(auto it = callbacks.begin(); it != callbacks.end(); ) {
+    auto it_current = it;
+    it++;
+    auto& [eventname, handler] = *it_current;
+    if (handler == ev_handler) {
+      callbacks.erase(it_current);
+    }
+  }
 
   callbackMutex.unlock();
 }

src/modules/hyprland/language.cpp

@@ -25,7 +25,13 @@ Language::Language(const std::string& id, const Bar& bar, const Json::Value& con
   AButton::update();
 
   // register for hyprland ipc
-  gIPC->registerForIPC("activelayout", [&](const std::string& ev) { this->onEvent(ev); });
+  gIPC->registerForIPC("activelayout", this);
+}
+
+Language::~Language() {
+  gIPC->unregisterForIPC(this);
+  // wait for possible event handler to finish
+  std::lock_guard<std::mutex> lg(mutex_);
 }
 
 auto Language::update() -> void {

src/modules/hyprland/window.cpp

@@ -25,7 +25,13 @@ Window::Window(const std::string& id, const Bar& bar, const Json::Value& config)
   ALabel::update();
 
   // register for hyprland ipc
-  gIPC->registerForIPC("activewindow", [&](const std::string& ev) { this->onEvent(ev); });
+  gIPC->registerForIPC("activewindow", this);
+}
+
+Window::~Window() {
+  gIPC->unregisterForIPC(this);
+  // wait for possible event handler to finish
+  std::lock_guard<std::mutex> lg(mutex_);
 }
 
 auto Window::update() -> void {
@@ -50,7 +56,9 @@ uint Window::getActiveWorkspaceID(std::string monitorName) {
   assert(json.isArray());
   auto monitor = std::find_if(json.begin(), json.end(),
                               [&](Json::Value monitor) { return monitor["name"] == monitorName; });
-  assert(monitor != std::end(json));
+  if(monitor == std::end(json)) {
+    return 0;
+  }
   return (*monitor)["activeWorkspace"]["id"].as<uint>();
 }