Running a Gtkmm Dialog fails

Question

I'm trying to pop up a dialog after setting up Gtkmm like so:

MainWindow::MainWindow() : public Gtk::Window { //etc etc

and in main()

Gtk::Main ginit(argc,argv);
MainWindow *mw = new MainWindow;  // delcared as extern in header as well for the dialog
ginit.run(*mw);

when the necessary event gets triggered, the following code should run, but fails. Which is strange since the example on http://library.gnome.org/devel/gtkmm-tutorial/2.21/sec-dialogs-filechooserdialog.html.en compiles and runs perfectly.

 Gtk::FileChooserDialog *dlg = new Gtk::FileChooserDialog(Glib::ustring("choose destination"), Gtk::FILE_CHOOSER_ACTION_SELECT_FOLDER);

  dlg->set_transient_for(*mw);

  dlg->add_button(Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);
  dlg->add_button(Glib::ustring("Select"), Gtk::RESPONSE_OK);
  dlg->show_all_children();

  int response =dlg->run();

According to GDB, it all fails on dlg->run(); And to make it more fun, it gives me one of two errors:

(PCollab:4583): GLib-GObject-CRITICAL **: g_object_ref: assertion `G_IS_OBJECT (object)' failed

(PCollab:4583): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `-g-type-private--GTypeFlags'

(PCollab:4583): GLib-GObject-CRITICAL **: g_signal_emit_valist: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(PCollab:4583): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed

(PCollab:4583): GLib-GObject-CRITICAL **: g_object_ref: assertion `G_IS_OBJECT (object)' failed

(PCollab:4583): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `(null)'

(PCollab:4583): GLib-GObject-CRITICAL **: g_signal_emit_valist: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(PCollab:4583): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed PCollab: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.0.

So i figured what the hell and ran

sudo xhost +

Which does some magic that allows the same program to connect twice to X11 (or so I read on the all-knowing internet) This has some effect, but not what I desire. Because now it gives me something far more cryptic:

../../src/xcb_io.c: process_responses: Assertion `(((long) (dpy->last_request_read) - (long)(dpy->request)) <= 0)' failed.

I'd assume that the first error means that mw doesn't point to a Gtk::Window as it isn't considered an object by gtk, but the fact remains that mw is shown on my screen perfectly without errors when i run Gtk::Main ginit(*mw); As I have not even the faintest idea what this means, I hope that some Gtk / X11 guru can point me in the right direction to fix my code.

Other details , i'm running Ubuntu Linux (amd64) with gcc 4.4.5 and gtkmm 2.4

Unless you're executing the program using another user than your X window system is running, xhost + doesn't has to do anything special or different for your application. What is the error shown in GDB in dlg->run()? — Diego Sevilla
@ptomato, The only thread in my program is the Gtk::Main loop which runs from my main() function, everything else is event-based and called through the gtk loop. — Michael
Could you simplify your program as much as you can and paste it in your question? You may even find the problem by doing these simplifications... — davidag

AzP AzP · Accepted Answer · 2011-10-06T14:30:52

MainWindow::MainWindow() : public Gtk::Window { //etc etc

This looks a bit strange, are you trying to inherit in the definition instead of the declaration? Or is it just a typo?

The example code in the (new) tutorial (for gtkmm 3) now looks like the following.

#include <gtkmm.h>

class ExampleWindow : public Gtk::Window
{
public:
  ExampleWindow();
  virtual ~ExampleWindow();

protected:
  //Signal handlers:
  void on_button_file_clicked();
  void on_button_folder_clicked();

  //Child widgets:
  Gtk::VButtonBox m_ButtonBox;
  Gtk::Button m_Button_File, m_Button_Folder;
};

Have you tried allocating the variables on the stack instead of on the heap? Like

  Gtk::FileChooserDialog dialog("Please choose a folder",
          Gtk::FILE_CHOOSER_ACTION_SELECT_FOLDER);
  dialog.set_transient_for(*this);

  //Add response buttons the the dialog:
  dialog.add_button(Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);
  dialog.add_button("Select", Gtk::RESPONSE_OK);

  int result = dialog.run();

instead of with new and pointers?

Running a Gtkmm Dialog fails

2 Answers