mirror of
https://github.com/servo/servo.git
synced 2025-06-06 16:45:39 +00:00
43 lines
1.4 KiB
Rust
43 lines
1.4 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
//! The `Castable` trait.
|
|
|
|
pub use dom::bindings::codegen::InheritTypes::*;
|
|
|
|
use dom::bindings::conversions::get_dom_class;
|
|
use dom::bindings::conversions::{DerivedFrom, IDLInterface};
|
|
use dom::bindings::reflector::Reflectable;
|
|
use std::mem;
|
|
|
|
/// A trait to hold the cast functions of IDL interfaces that either derive
|
|
/// or are derived from other interfaces.
|
|
pub trait Castable: IDLInterface + Reflectable + Sized {
|
|
/// Check whether a DOM object implements one of its deriving interfaces.
|
|
fn is<T>(&self) -> bool
|
|
where T: DerivedFrom<Self>
|
|
{
|
|
let class = unsafe { get_dom_class(self.reflector().get_jsobject().get()).unwrap() };
|
|
T::derives(class)
|
|
}
|
|
|
|
/// Cast a DOM object upwards to one of the interfaces it derives from.
|
|
fn upcast<T>(&self) -> &T
|
|
where T: Castable,
|
|
Self: DerivedFrom<T>
|
|
{
|
|
unsafe { mem::transmute(self) }
|
|
}
|
|
|
|
/// Cast a DOM object downwards to one of the interfaces it might implement.
|
|
fn downcast<T>(&self) -> Option<&T>
|
|
where T: DerivedFrom<Self>
|
|
{
|
|
if self.is::<T>() {
|
|
Some(unsafe { mem::transmute(self) })
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
}
|