Handle display connection loss gracefully instead of crashing

_codeql_detected_source_root

@@ -0,0 +1 @@
+.

include/client.hpp

@@ -20,6 +20,7 @@ class Client {
   static Client* inst();
   int main(int argc, char* argv[]);
   void reset();
+  ~Client();
 
   Glib::RefPtr<Gtk::Application> gtk_app;
   Glib::RefPtr<Gdk::Display> gdk_display;
@@ -58,6 +59,9 @@ class Client {
   std::string m_cssFile;
   sigc::connection monitor_added_connection_;
   sigc::connection monitor_removed_connection_;
+  guint gdk_log_handler_id_ = 0;
+  guint gtk_log_handler_id_ = 0;
+  guint default_log_handler_id_ = 0;
 };
 
 }  // namespace waybar

src/client.cpp

@@ -3,6 +3,7 @@
 #include <gtk-layer-shell.h>
 #include <spdlog/spdlog.h>
 
+#include <cstdlib>
 #include <iostream>
 #include <utility>
 
@@ -11,11 +12,68 @@
 #include "util/clara.hpp"
 #include "util/format.hpp"
 
+namespace {
+// Handler for GDK/GTK log messages to catch display connection errors
+void gdkLogHandler(const gchar* log_domain, GLogLevelFlags log_level, const gchar* message,
+                   gpointer user_data) {
+  // Check for display connection errors
+  // These error messages come from GDK's X11/Wayland backend when the display connection breaks
+  // Note: Error message format is consistent across GTK3 versions but may change in GTK4
+  if (message && (strstr(message, "Error reading events from display") != nullptr ||
+                  strstr(message, "Broken pipe") != nullptr)) {
+    spdlog::error("Display connection lost: {}. Exiting gracefully.", message);
+    // Request application shutdown
+    auto* client = waybar::Client::inst();
+    if (client && client->gtk_app) {
+      client->gtk_app->quit();
+    } else {
+      // Fallback if GTK app is not initialized yet
+      std::exit(1);
+    }
+    return;
+  }
+
+  // Forward other messages to spdlog with appropriate level
+  switch (log_level & G_LOG_LEVEL_MASK) {
+    case G_LOG_LEVEL_ERROR:
+    case G_LOG_LEVEL_CRITICAL:
+      if (message) spdlog::error("[{}] {}", log_domain ? log_domain : "GLib", message);
+      break;
+    case G_LOG_LEVEL_WARNING:
+      if (message) spdlog::warn("[{}] {}", log_domain ? log_domain : "GLib", message);
+      break;
+    case G_LOG_LEVEL_MESSAGE:
+    case G_LOG_LEVEL_INFO:
+      if (message) spdlog::info("[{}] {}", log_domain ? log_domain : "GLib", message);
+      break;
+    case G_LOG_LEVEL_DEBUG:
+      if (message) spdlog::debug("[{}] {}", log_domain ? log_domain : "GLib", message);
+      break;
+    default:
+      if (message) spdlog::trace("[{}] {}", log_domain ? log_domain : "GLib", message);
+      break;
+  }
+}
+}  // namespace
+
 waybar::Client* waybar::Client::inst() {
   static auto* c = new Client();
   return c;
 }
 
+waybar::Client::~Client() {
+  // Clean up log handlers
+  if (gdk_log_handler_id_ != 0) {
+    g_log_remove_handler("Gdk", gdk_log_handler_id_);
+  }
+  if (gtk_log_handler_id_ != 0) {
+    g_log_remove_handler("Gtk", gtk_log_handler_id_);
+  }
+  if (default_log_handler_id_ != 0) {
+    g_log_remove_handler(nullptr, default_log_handler_id_);
+  }
+}
+
 void waybar::Client::handleGlobal(void* data, struct wl_registry* registry, uint32_t name,
                                   const char* interface, uint32_t version) {
   auto* client = static_cast<Client*>(data);
@@ -268,9 +326,19 @@ int waybar::Client::main(int argc, char* argv[]) {
   if (!log_level.empty()) {
     spdlog::set_level(spdlog::level::from_str(log_level));
   }
+
   gtk_app = Gtk::Application::create(argc, argv, "fr.arouillard.waybar",
                                      Gio::APPLICATION_HANDLES_COMMAND_LINE);
 
+  // Install log handler to catch display connection errors
+  // This must be done after gtk_app is created so the handler can call gtk_app->quit()
+  gdk_log_handler_id_ = g_log_set_handler("Gdk", G_LOG_LEVEL_MASK, gdkLogHandler, nullptr);
+  gtk_log_handler_id_ = g_log_set_handler("Gtk", G_LOG_LEVEL_MASK, gdkLogHandler, nullptr);
+  // Only handle critical errors from other domains to avoid interfering with library error handling
+  default_log_handler_id_ = g_log_set_handler(nullptr, 
+      static_cast<GLogLevelFlags>(G_LOG_LEVEL_ERROR | G_LOG_LEVEL_CRITICAL), 
+      gdkLogHandler, nullptr);
+
   // Initialize Waybars GTK resources with our custom icons
   auto theme = Gtk::IconTheme::get_default();
   theme->add_resource_path("/fr/arouillard/waybar/icons");