Make XojMsgBox::showErrorAndQuit() gtk4-compatible

src/util/XojMsgBox.cpp

@@ -102,23 +102,22 @@ void XojMsgBox::askQuestionWithMarkup(GtkWindow* win, std::string_view maintext,
 }
 
 void XojMsgBox::showErrorAndQuit(std::string& msg, int exitCode) {
-    /*
-     * This should be used for fatal errors, typically in early GUI startup (missing UI main file or so).
-     *
-     * Todo(gtk4): Figure out how to use a non-blocking dialog that would survive past the `exit` call.
-     * Putting the `exit()` in a callback is no good, as normal execution would continue in the background, most likely
-     * leading to a SegFault: that would again kill the dialog.
-     */
     GtkWidget* dialog = gtk_message_dialog_new_with_markup(defaultWindow, GTK_DIALOG_MODAL, GTK_MESSAGE_ERROR,
                                                            GTK_BUTTONS_OK, nullptr);
 
-    auto formattedMsg = xoj::util::OwnedCString::assumeOwnership(g_markup_escape_text(msg.c_str(), -1));
-    gtk_message_dialog_set_markup(GTK_MESSAGE_DIALOG(dialog), formattedMsg.get());
-    if (defaultWindow != nullptr) {
-        gtk_window_set_transient_for(GTK_WINDOW(dialog), defaultWindow);
+    gtk_message_dialog_set_markup(GTK_MESSAGE_DIALOG(dialog), msg.c_str());
+
+    // We use a hack to ensure the app does not exit until the user has read the error message and closed the popup
+    bool done = false;
+
+    xoj::popup::PopupWindowWrapper<XojMsgBox> popup(GTK_DIALOG(dialog), [&done](int) { done = true; });
+
+    popup.show(defaultWindow);
+
+    while (!done) {
+        // Let the main loop run so the popup pops up and can be interacted with
+        g_main_context_iteration(g_main_context_default(), true);
     }
-    gtk_dialog_run(GTK_DIALOG(dialog));
-    gtk_widget_destroy(dialog);
 
     exit(exitCode);
 }

src/util/include/util/XojMsgBox.h

@@ -64,7 +64,10 @@ class XojMsgBox final {
     static void showMessageToUser(GtkWindow* win, const std::string& title, const std::string& msg,
                                   GtkMessageType type);
     static void showErrorToUser(GtkWindow* win, const std::string& msg);
-    static void showErrorAndQuit(std::string& msg, int exitCode);
+
+    /// @brief This should be used for fatal errors, typically in early GUI startup (missing UI main file or so).
+    [[noreturn]] static void showErrorAndQuit(std::string& msg, int exitCode);
+
     static void showPluginMessage(const std::string& pluginName, const std::string& msg, bool error = false);
     [[deprecated("Will be removed when porting to gtk4")]] static int askPluginQuestion(
             const std::string& pluginName, const std::string& msg, const std::vector<Button>& buttons,