Uniqueness of Gtk application without creating any window

Question

Is it possible to run only one copy of GTK application but without creating any windows? This example allows you to run several copies of the program, but I somehow need to enforce that only one be allowed to run.

#include <gtkmm.h>                                                                                                                                 

int                                                                                                                                                
main(int argc, char** argv)                                                                                                                        
{                                                                                                                                                  
    Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");
    app->hold();

    return app->run();                                                                                                                               
}

If I add a GTK window everything is working as I'd expect it to do. i.e. only one copy is running, the second one just exits. But my application lives in a system tray and doesn't create any windows at start.

#include <gtkmm.h>                                                                                                                                 

int                                                                                                                                                
main(int argc, char** argv)                                                                                                                        
{                                                                                                                                                  
    Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example");                                                  
    Gtk::Window window;                                                                                                                              

    return app->run(window);                                                                                                                         
}

Worron Worron · Accepted Answer · 2017-02-04T19:05:01

I'm not familiar with c++, but my suggestion is that you place hold method wrong. Only primary instance should be held. After second instance launched it raise 'activate' signal for primary instance. So place all you action in g_application_activate method seems like solution.

This is how it works with python, maybe this can help

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk

class Application(Gtk.Application):
    def __init__(self, *args, **kwargs):
        super().__init__(application_id="org.example.myapp")

    def do_activate(self):
        if not hasattr(self, "my_app_settings"):
            self.hold()
            self.my_app_settings = "Primary application instance."
            print(self.my_app_settings)
        else:
            print("Already running!")

app = Application()
app.run()

Uniqueness of Gtk application without creating any window

2 Answers