It might be lack of sleep, but I can’t figure this out.

I have a Label, and I want its text to be red when it represents an error, and I want it be green when it represent “good to go”.

I found search result for C and maybe a solution for Python, but nothing for Rust.

I tried manually setting the css-classes property and running queue_draw(); it didn’t work.

I can have a gtk::Box or a Frame that I place where the Label should go, then declare two Labels, and use set_child() to switch between them, but that seems like an ugly solution.

Do you have a solution?

  • d_k_bo@feddit.org
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    7 hours ago

    Just use label.add_css_class(), label.remove_css_class() or label.set_css_classes() and make sure to properly load your CSS style sheets, this is usually done by including them as a resource alongside .ui files and icons. If you are using libadwaita, you can also use its predefined style classes.

    full example (requires nightly toolchain)
    #!/usr/bin/env -S cargo +nightly -Zscript
    ---
    [dependencies]
    gtk = { package = "gtk4", version = "0.9.3", features = ["v4_12"] }
    ---
    
    use gtk::{glib, prelude::*};
    
    const STYLESHEET: &str = r#"
    .green {
        color: green;
    }
    .red {
        color: red;
    }
    "#;
    
    fn main() -> glib::ExitCode {
        let app = gtk::Application::builder()
            .application_id("org.example.HelloWorld")
            .build();
    
        app.connect_activate(|app| {
            let window = gtk::ApplicationWindow::builder()
                .application(app)
                .title("Hello, World!")
                .build();
    
            // Stylesheets are usually bundled with application resources
            // and automatically loaded
            let css_provider = gtk::CssProvider::new();
            css_provider.load_from_string(STYLESHEET);
            gtk::style_context_add_provider_for_display(
                &RootExt::display(&window),
                &css_provider,
                0
            );
    
            let box_ = gtk::Box::new(gtk::Orientation::Vertical, 6);
    
            let label = gtk::Label::builder()
                .label("Hello, World")
                .css_classes(["green"].as_slice())
                .build();
            box_.append(&label);
    
    
            let button = gtk::Button::builder()
                .label("Toggle Color")
                .build();
            box_.append(&button);
    
            button.connect_clicked(glib::clone!(#[weak] label, move |_| {
                if label.has_css_class("red") {
                    label.add_css_class("green");
                    label.remove_css_class("red");
                } else {
                    label.add_css_class("red");
                    label.remove_css_class("green");
                }
            }));
    
            window.set_child(Some(&box_));
            window.present();
        });
    
        app.run()
    }
    
    • Doods@infosec.pubOP
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      18 minutes ago

      This is embarrassing, but when was it not?

      I have to add a “.” before the name of a css class, I must learn my tools.