glib/subclass/

interface.rs

// Take a look at the license at the top of the repository in the LICENSE file.

use std::{marker, mem};

use super::{InitializingType, Signal, types::InterfaceStruct};
use crate::{
    Object, ParamSpec, Type, TypeFlags, TypeInfo, ffi, gobject_ffi, prelude::*, translate::*,
};

// rustdoc-stripper-ignore-next
/// Trait for a type list of prerequisite object types.
pub trait PrerequisiteList {
    // rustdoc-stripper-ignore-next
    /// Returns the list of types for this list.
    fn types() -> Vec<Type>;
}

impl PrerequisiteList for () {
    fn types() -> Vec<Type> {
        vec![]
    }
}

impl<T: ObjectType> PrerequisiteList for (T,) {
    fn types() -> Vec<Type> {
        vec![T::static_type()]
    }
}

// Generates all the PrerequisiteList impls for prerequisite_lists of arbitrary sizes based on a list of type
// parameters like A B C. It would generate the impl then for (A, B) and (A, B, C).
macro_rules! prerequisite_list_trait(
    ($name1:ident, $name2: ident, $($name:ident),*) => (
        prerequisite_list_trait!(__impl $name1, $name2; $($name),*);
    );
    (__impl $($name:ident),+; $name1:ident, $($name2:ident),*) => (
        prerequisite_list_trait_impl!($($name),+);
        prerequisite_list_trait!(__impl $($name),+ , $name1; $($name2),*);
    );
    (__impl $($name:ident),+; $name1:ident) => (
        prerequisite_list_trait_impl!($($name),+);
        prerequisite_list_trait_impl!($($name),+, $name1);
    );
);

// Generates the impl block for PrerequisiteList on prerequisite_lists or arbitrary sizes based on its
// arguments. Takes a list of type parameters as parameters, e.g. A B C
// and then implements the trait on (A, B, C).
macro_rules! prerequisite_list_trait_impl(
    ($($name:ident),+) => (
        impl<$($name: ObjectType),+> PrerequisiteList for ( $($name),+ ) {
            fn types() -> Vec<Type> {
                vec![$($name::static_type()),+]
            }
        }
    );
);

prerequisite_list_trait!(A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S);

/// Type methods required for an [`ObjectInterface`] implementation.
///
/// This is usually generated by the [`#[object_interface]`](crate::object_interface) attribute macro.
pub unsafe trait ObjectInterfaceType {
    /// Returns the `glib::Type` ID of the interface.
    ///
    /// This will register the type with the type system on the first call.
    #[doc(alias = "get_type")]
    fn type_() -> Type;
}

/// The central trait for defining a `GObject` interface.
///
/// Links together the type name, the empty instance and class structs for type
/// registration and allows hooking into various steps of the type registration
/// and initialization.
///
/// See [`register_interface`] for registering an implementation of this trait
/// with the type system.
///
/// [`register_interface`]: fn.register_interface.html
pub trait ObjectInterface: ObjectInterfaceType + Sized + 'static {
    /// `GObject` type name.
    ///
    /// This must be unique in the whole process.
    const NAME: &'static str;

    // rustdoc-stripper-ignore-next
    /// Allow name conflicts for this class.
    ///
    /// By default, trying to register a type with a name that was registered before will panic. If
    /// this is set to `true` then a new name will be selected by appending a counter.
    ///
    /// This is useful for defining new types in Rust library crates that might be linked multiple
    /// times in the same process.
    ///
    /// A consequence of setting this to `true` is that it's not guaranteed that
    /// `glib::Type::from_name(Self::NAME).unwrap() == Self::type_()`.
    ///
    /// Note that this is not allowed for dynamic types. If a dynamic type is registered and a type
    /// with that name exists already, it is assumed that they're the same.
    ///
    /// Optional.
    const ALLOW_NAME_CONFLICT: bool = false;

    /// Prerequisites for this interface.
    ///
    /// Any implementer of the interface must be a subclass of the prerequisites or implement them
    /// in case of interfaces.
    type Prerequisites: PrerequisiteList;

    // rustdoc-stripper-ignore-next
    /// The C instance struct. This is usually either `std::ffi::c_void` or a newtype wrapper
    /// around it.
    ///
    /// Optional
    type Instance;

    // rustdoc-stripper-ignore-next
    /// The C class struct.
    type Interface: InterfaceStruct<Type = Self>;

    /// Additional type initialization.
    ///
    /// This is called right after the type was registered and allows
    /// interfaces to do additional type-specific initialization.
    ///
    /// Optional
    fn type_init(_type_: &mut InitializingType<Self>) {}

    /// Interface initialization.
    ///
    /// This is called after `type_init` and before the first implementor
    /// of the interface is created. Interfaces can use this to do interface-
    /// specific initialization, e.g. for installing signals on the interface,
    /// and for setting default implementations of interface functions.
    ///
    /// Optional
    fn interface_init(_klass: &mut Self::Interface) {}

    /// Properties installed for this interface.
    ///
    /// All implementors of the interface must provide these properties.
    fn properties() -> &'static [ParamSpec] {
        &[]
    }

    /// Signals installed for this interface.
    fn signals() -> &'static [Signal] {
        &[]
    }
}

pub trait ObjectInterfaceExt: ObjectInterface {
    /// Get interface from an instance.
    ///
    /// This will panic if `obj` does not implement the interface.
    #[inline]
    fn from_obj<T: IsA<Object>>(obj: &T) -> &Self {
        assert!(obj.as_ref().type_().is_a(Self::type_()));

        unsafe {
            let klass = (*(obj.as_ptr() as *const gobject_ffi::GTypeInstance)).g_class;
            let interface =
                gobject_ffi::g_type_interface_peek(klass as *mut _, Self::type_().into_glib());
            debug_assert!(!interface.is_null());
            &*(interface as *const Self)
        }
    }
}

impl<T: ObjectInterface> ObjectInterfaceExt for T {}

unsafe extern "C" fn interface_init<T: ObjectInterface>(
    klass: ffi::gpointer,
    _klass_data: ffi::gpointer,
) {
    unsafe {
        let iface = &mut *(klass as *mut T::Interface);

        let pspecs = <T as ObjectInterface>::properties();
        for pspec in pspecs {
            gobject_ffi::g_object_interface_install_property(
                iface as *mut T::Interface as *mut _,
                pspec.to_glib_none().0,
            );
        }

        let type_ = T::type_();
        let signals = <T as ObjectInterface>::signals();
        for signal in signals {
            signal.register(type_);
        }

        T::interface_init(iface);
    }
}

/// Register a `glib::Type` ID for `T::Class`.
///
/// This must be called only once and will panic on a second call.
///
/// The [`object_interface!`] macro will create a `type_()` function around this, which will
/// ensure that it's only ever called once.
///
/// [`object_interface!`]: ../../macro.object_interface.html
pub fn register_interface<T: ObjectInterface>() -> Type {
    assert_eq!(mem::size_of::<T>(), 0);

    unsafe {
        use std::ffi::CString;

        let type_name = if T::ALLOW_NAME_CONFLICT {
            let mut i = 0;
            loop {
                let type_name = CString::new(if i == 0 {
                    T::NAME.to_string()
                } else {
                    format!("{}-{}", T::NAME, i)
                })
                .unwrap();
                if gobject_ffi::g_type_from_name(type_name.as_ptr()) == gobject_ffi::G_TYPE_INVALID
                {
                    break type_name;
                }
                i += 1;
            }
        } else {
            let type_name = CString::new(T::NAME).unwrap();
            assert_eq!(
                gobject_ffi::g_type_from_name(type_name.as_ptr()),
                gobject_ffi::G_TYPE_INVALID,
                "Type {} has already been registered",
                type_name.to_str().unwrap()
            );

            type_name
        };

        let type_ = gobject_ffi::g_type_register_static_simple(
            Type::INTERFACE.into_glib(),
            type_name.as_ptr(),
            mem::size_of::<T::Interface>() as u32,
            Some(interface_init::<T>),
            0,
            None,
            0,
        );

        let prerequisites = T::Prerequisites::types();
        for prerequisite in prerequisites {
            gobject_ffi::g_type_interface_add_prerequisite(type_, prerequisite.into_glib());
        }

        let type_ = Type::from_glib(type_);
        assert!(type_.is_valid());

        T::type_init(&mut InitializingType::<T>(type_, marker::PhantomData));

        type_
    }
}

/// Registers a `glib::Type` ID for `T::Class` as a dynamic type.
///
/// An object interface must be explicitly registered as a dynamic type when
/// the system loads the implementation by calling [`TypePluginImpl::use_`] or
/// more specifically [`TypeModuleImpl::load`]. Therefore, unlike for object
/// interfaces registered as static types, object interfaces registered as
/// dynamic types can be registered several times.
///
/// The [`object_interface_dynamic!`] macro helper attribute will create
/// `register_interface()` and `on_implementation_load()` functions around this,
/// which will ensure that the function is called when necessary.
///
/// [`object_interface_dynamic!`]: ../../../glib_macros/attr.object_interface.html
/// [`TypePluginImpl::use_`]: ../type_plugin/trait.TypePluginImpl.html#method.use_
/// [`TypeModuleImpl::load`]: ../type_module/trait.TypeModuleImpl.html#method.load
pub fn register_dynamic_interface<P: DynamicObjectRegisterExt, T: ObjectInterface>(
    type_plugin: &P,
) -> Type {
    assert_eq!(mem::size_of::<T>(), 0);

    unsafe {
        use std::ffi::CString;

        let type_name = CString::new(T::NAME).unwrap();

        let already_registered =
            gobject_ffi::g_type_from_name(type_name.as_ptr()) != gobject_ffi::G_TYPE_INVALID;

        let type_info = TypeInfo(gobject_ffi::GTypeInfo {
            class_size: mem::size_of::<T::Interface>() as u16,
            class_init: Some(interface_init::<T>),
            ..TypeInfo::default().0
        });

        // registers the interface within the `type_plugin`
        let type_ = type_plugin.register_dynamic_type(
            Type::INTERFACE,
            type_name.to_str().unwrap(),
            &type_info,
            TypeFlags::ABSTRACT,
        );

        let prerequisites = T::Prerequisites::types();
        for prerequisite in prerequisites {
            // adding prerequisite interface can be done only once
            if !already_registered {
                gobject_ffi::g_type_interface_add_prerequisite(
                    type_.into_glib(),
                    prerequisite.into_glib(),
                );
            }
        }

        assert!(type_.is_valid());

        T::type_init(&mut InitializingType::<T>(type_, marker::PhantomData));

        type_
    }
}