Module glib::subclass

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Expand description

Module containing infrastructure for subclassing GObjects and registering boxed types.

Example for registering a glib::Object subclass

The following code implements a subclass of glib::Object with a string-typed “name” property.

use glib::prelude::*;
use glib::subclass;
use glib::subclass::prelude::*;
use glib::{Variant, VariantType};

use std::cell::{Cell, RefCell};

#[derive(Debug, Eq, PartialEq, Clone, Copy, glib::Enum)]
#[repr(u32)]
// type_name: GType name of the enum (mandatory)
#[enum_type(name = "SimpleObjectAnimal")]
enum Animal {
    Goat = 0,
    #[enum_value(name = "The Dog")]
    Dog = 1,
    // name: the name of the GEnumValue (optional), default to the enum name in CamelCase
    // nick: the nick of the GEnumValue (optional), default to the enum name in kebab-case
    #[enum_value(name = "The Cat", nick = "chat")]
    Cat = 2,
}

impl Default for Animal {
    fn default() -> Self {
        Animal::Goat
    }
}

#[glib::flags(name = "MyFlags")]
enum MyFlags {
    #[flags_value(name = "Flag A", nick = "nick-a")]
    A = 0b00000001,
    #[flags_value(name = "Flag B")]
    B = 0b00000010,
    #[flags_value(skip)]
    AB = Self::A.bits() | Self::B.bits(),
    C = 0b00000100,
}

impl Default for MyFlags {
    fn default() -> Self {
        MyFlags::A
    }
}

mod imp {
    use super::*;

    // This is the struct containing all state carried with
    // the new type. Generally this has to make use of
    // interior mutability.
    // If it implements the `Default` trait, then `Self::default()`
    // will be called every time a new instance is created.
    #[derive(Default)]
    pub struct SimpleObject {
        name: RefCell<Option<String>>,
        animal: Cell<Animal>,
        flags: Cell<MyFlags>,
        variant: RefCell<Option<Variant>>,
    }

    // ObjectSubclass is the trait that defines the new type and
    // contains all information needed by the GObject type system,
    // including the new type's name, parent type, etc.
    // If you do not want to implement `Default`, you can provide
    // a `new()` method.
    #[glib::object_subclass]
    impl ObjectSubclass for SimpleObject {
        // This type name must be unique per process.
        const NAME: &'static str = "SimpleObject";

        type Type = super::SimpleObject;

        // The parent type this one is inheriting from.
        // Optional, if not specified it defaults to `glib::Object`
        type ParentType = glib::Object;

        // Interfaces this type implements.
        // Optional, if not specified it defaults to `()`
        type Interfaces = ();
    }

    // Trait that is used to override virtual methods of glib::Object.
    impl ObjectImpl for SimpleObject {
        // Called once in the very beginning to list all properties of this class.
        fn properties() -> &'static [glib::ParamSpec] {
            use once_cell::sync::Lazy;
            static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
                vec![
                    glib::ParamSpecString::builder("name")
                        .build(),
                    glib::ParamSpecEnum::builder::<Animal>("animal", Animal::default())
                        .build(),
                    glib::ParamSpecFlags::builder::<MyFlags>("flags")
                        .default_value(MyFlags::default())
                        .build(),
                    glib::ParamSpecVariant::builder("variant", glib::VariantTy::ANY)
                        .build(),
                ]
            });

            PROPERTIES.as_ref()
        }

        // Called whenever a property is set on this instance. The id
        // is the same as the index of the property in the PROPERTIES array.
        fn set_property(&self, _id: usize, value: &glib::Value, pspec: &glib::ParamSpec) {
            match pspec.name() {
                "name" => {
                    let name = value
                        .get()
                        .expect("type conformity checked by `Object::set_property`");
                    self.name.replace(name);
                },
                "animal" => {
                    let animal = value
                        .get()
                        .expect("type conformity checked by `Object::set_property`");
                    self.animal.replace(animal);
                },
                "flags" => {
                    let flags = value
                        .get()
                        .expect("type conformity checked by `Object::set_property`");
                    self.flags.replace(flags);
                },
                "variant" => {
                    let variant = value
                        .get()
                        .expect("type conformity checked by `Object::set_property`");
                    self.variant.replace(variant);
                },
                _ => unimplemented!(),
            }
        }

        // Called whenever a property is retrieved from this instance. The id
        // is the same as the index of the property in the PROPERTIES array.
        fn property(&self, _id: usize, pspec: &glib::ParamSpec) -> glib::Value {
            match pspec.name() {
                "name" => self.name.borrow().to_value(),
                "animal" => self.animal.get().to_value(),
                "flags" => self.flags.get().to_value(),
                "variant" => self.variant.borrow().to_value(),
                _ => unimplemented!(),
            }
        }

        // Called right after construction of the instance.
        fn constructed(&self) {
            // Chain up to the parent type's implementation of this virtual
            // method.
            self.parent_constructed();

            // And here we could do our own initialization.
        }
    }
}

// Optionally, define a wrapper type to make it more ergonomic to use from Rust
glib::wrapper! {
    pub struct SimpleObject(ObjectSubclass<imp::SimpleObject>);
}

impl SimpleObject {
    // Create an object instance of the new type.
    pub fn new() -> Self {
        glib::Object::new(&[])
    }
}

pub fn main() {
    let obj = SimpleObject::new();

    // Get the name property and change its value.
    assert_eq!(obj.property::<Option<String>>("name"), None);
    obj.set_property("name", "test");
    assert_eq!(&obj.property::<String>("name"), "test");

    assert_eq!(obj.property::<Animal>("animal"), Animal::Goat);
    obj.set_property("animal", Animal::Cat);
    assert_eq!(obj.property::<Animal>("animal"), Animal::Cat);

    assert_eq!(obj.property::<MyFlags>("flags"), MyFlags::A);
    obj.set_property("flags", MyFlags::B);
    assert_eq!(obj.property::<MyFlags>("flags"), MyFlags::B);
}

Example for registering a boxed type for a Rust struct

The following code boxed type for a tuple struct around String and uses it in combination with glib::Value.

use glib::prelude::*;
use glib::subclass;
use glib::subclass::prelude::*;

#[derive(Clone, Debug, PartialEq, Eq, glib::Boxed)]
#[boxed_type(name = "MyBoxed")]
struct MyBoxed(String);

pub fn main() {
    assert!(MyBoxed::static_type().is_valid());

    let b = MyBoxed(String::from("abc"));
    let v = b.to_value();
    let b2 = v.get::<&MyBoxed>().unwrap();
    assert_eq!(&b, b2);
}

Re-exports

Modules

  • basic
    This module contains basic instance and class structs to be used for GObject subclasses that don’t require any additional data in these structs and don’t provide any new virtual methods.
  • boxed
    Module for registering boxed types for Rust types.
  • interface
  • object
    Module that contains all types needed for creating a direct subclass of GObject or implementing virtual methods of it.
  • prelude
    Prelude that re-exports all important traits from this crate.
  • shared
    Module for registering shared types for Rust types.
  • signal
  • types
    Module that contains the basic infrastructure for subclassing GObject.

Structs