Why can't I use clone!() in gtk4 for Rust?

Question

I've just installed gtk4 over gtk for Rust and wrote a hello world program to test if it works. I want to use the clone macro to pass a weak reference for my button but, its not recognising the clone in gtk4::glib and says I have to use gtk::glib and glib::clone but does not work because clone isn't in gtk4.

The error I get in my editor is:

   glib needs to be in scope, so unless it's one of the direct crate 
   dependencies, you need to import it because clone! is using it. 
   For example: use gtk::glib;

Here is my code:

use glib::clone;
use gtk::prelude::*;
use gtk::{glib, Application};
use gtk4 as gtk;

fn main() {
    let app = Application::builder().application_id("hello-workd").build();

    app.connect_activate(build_ui);
    app.run();
}

fn build_ui(app: &gtk4::Application) {
    let button = gtk::Button::with_label("Hello World!");

    //error here
    button.connect_clicked(clone!(@weak button => move |_| {
        button.set_label("Hello to you!")
    }));

    let window = gtk::ApplicationWindow::builder()
        .application(app)
        .title("Hello World App")
        .child(&button)
        .build();

    window.present();
}

The program compiles and runs but I get the following warnings in my terminal:

GLib-GIO-CRITICAL **: 
g_application_set_application_id: assertion 'application_id == 
NULL || g_application_id_is_valid (application_id)' failed

and

Gtk-WARNING **: Unknown key gtk-modules in 
/home/../.config/gtk-4.0/settings.ini

Is there a way I can use gtk4 instead of gtk?

Please add the full error message generated by `cargo build` as text into your question by [edit]ing it. — cafce25, Mar 26 '23 at 19:22
The macro `clone!` is in `glib`, not in `gtk4`, but while `glib` is available as a re-export in `gtk4::glib` maybe that will not work for a macro. Try adding `glib` as a dependency in your `Cargo.toml` file. — rodrigo, Mar 26 '23 at 19:27
I added glib = "0.17.5" as a dependency in my Cargo.toml file and doesn't change the error in my editor; the program runs but I get the warnings that I added to the question — Shane Gervais, Mar 26 '23 at 19:41

cafce25 · Accepted Answer · 2023-03-26T20:31:30.350

1

The in editor message is only a notice (which I also cannot reproduce), there is nothing to be done about that. The real error is that "hello-workd" isn't a valid application id:

Application identifiers are composed of 1 or more elements separated by a period (.) character. All elements must contain at least one character.

Each element must only contain the ASCII characters [A-Z][a-z][0-9]_-, with - discouraged in new application identifiers. Each element must not begin with a digit.

Application identifiers must contain at least one . (period) character (and thus at least two elements).

Application identifiers must not begin with a . (period) character.

Application identifiers must not exceed 255 characters.

Specifically it does not consist of two elements, try "hello.workd" instead.

edited Mar 26 '23 at 20:31

answered Mar 26 '23 at 20:24

cafce25

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Ah thank you so much! I'm using vs code and its highlight that line in red so I thought it was an error. I didn't now much about APP_ID's thanks! – Shane Gervais Mar 26 '23 at 21:04
What about the GTK warning I'm getting? – Shane Gervais Mar 26 '23 at 21:06
I suggest you read it, look at the files it mentions, it's unrelated to your code. – cafce25 Mar 27 '23 at 00:08

score -1 · Answer 2 · answered Mar 26 '23 at 20:17

The clone! macro is actually defined in the glib crate and not in gtk. Therefore, you need to import glib::clone instead of gtk::glib.

To use gtk4 instead of gtk, you need to update your imports and code to use the new API...

use gtk::prelude::*;
use gtk::{Application, Button};
use glib::clone;

fn main() {
    let app = Application::builder()
        .application_id("hello-workd")
        .build();

    app.connect_activate(build_ui);
    app.run();
}

fn build_ui(app: &Application) {
    let button = Button::with_label("Hello World!");

    button.connect_clicked(clone!(@weak button => move |_| {
        button.set_label("Hello to you!")
    }));

    let window = gtk::ApplicationWindow::builder()
        .application(app)
        .title("Hello World App")
        .child(&button)
        .build();

    window.show();
}

This doesn't solve anything since OP is already using the reexport `gtk4::glib` which would work if it weren't for the real error that their `application_id` is invalid. — cafce25, Mar 26 '23 at 20:27

Why can't I use clone!() in gtk4 for Rust?

2 Answers2