Derive Macro CompositeTemplate 

#[derive(CompositeTemplate)]
{
    // Attributes available to this derive:
    #[template]
    #[template_child]
}

Derive macro for using a composite template in a widget.

The template attribute specifies where the template should be loaded from; it can be a file, a resource, or a string.

The template_child attribute is used to mark all internal widgets we need to have programmatic access to. It can take two parameters:

• id which defaults to the item name if not defined
• internal whether the child should be accessible as an “internal-child”, defaults to false

Example

Specify that MyWidget is using a composite template and load the template file the composite_template.ui file.

Then, in the ObjectSubclass implementation you will need to call bind_template in the class_init function, and init_template in instance_init function.

use gtk::{glib, prelude::*, subclass::prelude::*};

mod imp {
    use super::*;

    #[derive(Debug, Default, gtk::CompositeTemplate)]
    #[template(file = "test/template.ui")]
    pub struct MyWidget {
        #[template_child]
        pub label: TemplateChild<gtk::Label>,
        #[template_child(id = "my_button_id")]
        pub button: TemplateChild<gtk::Button>,
    }

    #[glib::object_subclass]
    impl ObjectSubclass for MyWidget {
        const NAME: &'static str = "MyWidget";
        type Type = super::MyWidget;
        type ParentType = gtk::Box;

        fn class_init(klass: &mut Self::Class) {
            klass.bind_template();
        }

        fn instance_init(obj: &glib::subclass::InitializingObject<Self>) {
            obj.init_template();
        }
    }

    impl ObjectImpl for MyWidget {}
    impl WidgetImpl for MyWidget {}
    impl BoxImpl for MyWidget {}
}

glib::wrapper! {
    pub struct MyWidget(ObjectSubclass<imp::MyWidget>)
    @extends gtk::Widget, gtk::Box,
    @implements gtk::Accessible, gtk::Buildable, gtk::ConstraintTarget;
}

impl MyWidget {
    pub fn new() -> Self {
        glib::Object::new()
    }
}

The CompositeTemplate macro can also be used with Blueprint if the feature blueprint is enabled. you can use string or file relative to the project directory but not resource

use gtk::{glib, prelude::*, subclass::prelude::*};

mod imp {
    use super::*;

    #[derive(Debug, Default, gtk::CompositeTemplate)]
    #[template(string = "
    using Gtk 4.0;
    template $MyWidget : Widget {
        Label label {
            label: 'foobar';
        }

        Label my_label2 {
            label: 'foobaz';
        }
    }
    ")]
    pub struct MyWidget {
        #[template_child]
        pub label: TemplateChild<gtk::Label>,
        #[template_child(id = "my_label2")]
        pub label2: gtk::TemplateChild<gtk::Label>,
    }

    #[glib::object_subclass]
    impl ObjectSubclass for MyWidget {
        const NAME: &'static str = "MyWidget";
        type Type = super::MyWidget;
        type ParentType = gtk::Widget;
        fn class_init(klass: &mut Self::Class) {
            klass.bind_template();
        }
        fn instance_init(obj: &glib::subclass::InitializingObject<Self>) {
            obj.init_template();
        }
    }

    impl ObjectImpl for MyWidget {
        fn dispose(&self) {
            while let Some(child) = self.obj().first_child() {
                child.unparent();
            }
        }
    }
    impl WidgetImpl for MyWidget {}
}

glib::wrapper! {
    pub struct MyWidget(ObjectSubclass<imp::MyWidget>)
    @extends gtk::Widget,
    @implements gtk::Accessible, gtk::Buildable, gtk::ConstraintTarget;
}