fix: handle X server disconnection gracefully

shell/CMakeLists.txt

@@ -4,6 +4,7 @@
 
 find_package(Dtk${DTK_VERSION_MAJOR} COMPONENTS Widget REQUIRED)
 find_package(Qt${QT_VERSION_MAJOR} ${REQUIRED_QT_VERSION} REQUIRED COMPONENTS Widgets Gui WaylandClient)
+pkg_check_modules(X11 REQUIRED IMPORTED_TARGET x11)
 find_package(TreelandProtocols REQUIRED)
 pkg_check_modules(WaylandClient REQUIRED IMPORTED_TARGET wayland-client)
 
@@ -46,6 +47,7 @@ target_link_libraries(dde-shell PRIVATE
     Dtk${DTK_VERSION_MAJOR}::Widget
     Qt${QT_VERSION_MAJOR}::DBus
     PkgConfig::WaylandClient
+    PkgConfig::X11
 )
 
 configure_file(${CMAKE_SOURCE_DIR}/misc/dde-shell-plugin@.service.in

shell/main.cpp

@@ -13,12 +13,14 @@
 #include <QQuickWindow>
 #include <QWindow>
 
 #include <csignal>
 #include <iostream>
 
+#include <X11/Xlib.h>
+
 #include "applet.h"
 #include "containment.h"
 #include "pluginloader.h"
 #include "appletloader.h"
 #include "qmlengine.h"
 #include "shell.h"
@@ -46,6 +48,28 @@
     QLoggingCategory::setFilterRules("*.debug=false");
 }
 
+// Handle X server disconnection gracefully.
+// When X server is killed (e.g. init 3), libX11's _XDefaultIOError calls exit(),
+// bypassing Qt's normal shutdown. This causes plugins to be destroyed during global
+// destructors when objects are already partially destroyed, leading to SIGSEGV.
+//
+// By installing a custom X I/O error handler, we prevent exit() from being called
+// and instead trigger a clean Qt shutdown via quit(), which fires aboutToQuit
+// and allows plugins to be properly destroyed.
+static int xio_error_handler(Display * /*dpy*/)
+{
+    qCCritical(dsLog) << "X I/O error detected, shutting down gracefully.";
+    QCoreApplication::quit();
+    return 0;
+}
+
+static void sigpipe_handler(int /*sig*/)
+{
+    // 信号处理函数中禁止调用非异步信号安全函数（如 qCCritical），
+    // 否则在持有相关锁时触发信号会导致死锁。
+    QCoreApplication::quit();
+}
+
 class AppletManager
 {
 public:
@@ -218,5 +242,19 @@
         manager.quit();
     });
 
+    // Install X11-specific error handlers to prevent exit() from being called
+    // when X server is killed (e.g. during init 3 → init 5 switch).
+    // On Wayland, these are not needed as the error path is different.
+    if (QGuiApplication::platformName().startsWith(QStringLiteral("xcb"))) {
+        XSetIOErrorHandler(xio_error_handler);
+
+        struct sigaction sa;
+        memset(&sa, 0, sizeof(sa));
+        sa.sa_handler = sigpipe_handler;
+        sigemptyset(&sa.sa_mask);
+        sa.sa_flags = 0;
+        sigaction(SIGPIPE, &sa, nullptr);
+    }
+
     return a.exec();
 }