GtkGesture in a Rust app not working

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Hi,
I am trying to monitor a gesture in a gtk-rs app and running into an issue getting any of the callbacks to run. Does anyone have an example where a GtkGesure is used in a Rust app? Below is the code that is not working. I am attempting to monitor both mouse and touch drags over a generic area. Am I missing something with how the GtkGesure classes are supposed to operate?

fn main() {
    let application = Application::new(Some("org.epic.overlay.dragtest"), Default::default())
        .expect("failed to initialize GTK application");
    application.connect_activate(|app| {
        let glade_src = include_str!("gest_test_layout.glade"); // glade set up
        let builder = gtk::Builder::from_string(glade_src); // builder set up
        let window: gtk::ApplicationWindow = builder.get_object("main_window").unwrap(); // main window upwrap from glade
        let area: gtk::DrawingArea = builder.get_object("drawing_area").unwrap();
        let area_drag_ges: gtk::GestureDrag = gtk::GestureDrag::new(&area);

        //back_image_long_p.set_propagation_phase(gtk::PropagationPhase::Bubble);
        //area_drag_ges.set_touch_only(false);

        area_drag_ges.connect_drag_begin(move |gest, x, y| {
            println!("X Begin {:?}", x);
            println!("Y Begin {:?}", y);
        });
        area_drag_ges.connect_drag_update(move |gest, x, y| {
            println!("X up {:?}", x);
            println!("Y up {:?}", y);
        });
        area_drag_ges.connect_drag_end(move |gest, x, y| {
            println!("X End {:?}", x);
            println!("Y End {:?}", y);
        });
        window.set_application(Some(app));
        window.show_all();
    });
    application.run(&args().collect::<Vec<_>>());
}
1 Like
2

You need to keep a reference to the gtk::GestureDrag—typically in the widget that uses it—otherwise they’ll just be dropped when the scope ends.

2 Likes
3

I am a little confused about how to accomplish this in Rust. I would think there is a cleaner option than going directly to the external function.

4

Create a struct that holds the window and the gesture instances, and then keep it around? I mean: how to structure a Rust code base is entirely up to you.

All you need to do is to ensure that objects exist outside of the inner scope of your callback.

That’s a very bad idea; that function is really just for C convenience, and should never be used by anything else.

5

Store the gesture somewhere in your application state next to other things you have to keep around.

6

Thank you for the help. As a quick fix I was able to just run the “gtk::main()” loop at the end of the closure to keep everything in scope.

7

No, please, that’s a terrible solution. You’re literally running a main loop inside another main loop. Don’t ever do that.

1 Like
8

I should have referred to it as a temporary dirty quick fix. I have always just used the glade builder object within the scope of the connect_activate callback. Would I want to declare the builder, window and widgets on the same level as the application and then just attach the window and show it within the callback?

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