GtkMessageDialog convenient message window #GtkMessageDialog presents a dialog with an image representing the type of message (Error, Question, etc.) alongside some message text. It's simply a convenience widget; you could construct the equivalent of #GtkMessageDialog from #GtkDialog without too much effort, but #GtkMessageDialog saves typing. The easiest way to do a modal message dialog is to use gtk_dialog_run(), though you can also pass in the GTK_DIALOG_MODAL flag, gtk_dialog_run() automatically makes the dialog modal and waits for the user to respond to it. gtk_dialog_run() returns when any dialog button is clicked. dialog = gtk_message_dialog_new (main_application_window, GTK_DIALOG_DESTROY_WITH_PARENT, GTK_MESSAGE_ERROR, GTK_BUTTONS_CLOSE, "Error loading file '%s': %s", filename, g_strerror (errno)); gtk_dialog_run (GTK_DIALOG (dialog)); gtk_widget_destroy (dialog); You might do a non-modal #GtkMessageDialog as follows: dialog = gtk_message_dialog_new (main_application_window, GTK_DIALOG_DESTROY_WITH_PARENT, GTK_MESSAGE_ERROR, GTK_BUTTONS_CLOSE, "Error loading file '%s': %s", filename, g_strerror (errno)); /* Destroy the dialog when the user responds to it (e.g. clicks a button) */ gtk_signal_connect_object (GTK_OBJECT (dialog), "response", GTK_SIGNAL_FUNC (gtk_widget_destroy), GTK_OBJECT (dialog)); #GtkDialog The type of message being displayed in the dialog. @GTK_MESSAGE_INFO: Informational message @GTK_MESSAGE_WARNING: Nonfatal warning message @GTK_MESSAGE_QUESTION: Question requiring a choice @GTK_MESSAGE_ERROR: Fatal error message Prebuilt sets of buttons for the dialog. If none of these choices are appropriate, simply use GTK_BUTTONS_NONE then call gtk_dialog_add_buttons(). @GTK_BUTTONS_NONE: no buttons at all @GTK_BUTTONS_OK: an OK button @GTK_BUTTONS_CLOSE: a Close button @GTK_BUTTONS_CANCEL: a Cancel button @GTK_BUTTONS_YES_NO: Yes and No buttons @GTK_BUTTONS_OK_CANCEL: OK and Cancel buttons @parent: @flags: @type: @buttons: @message_format: @Varargs: @Returns: