mirror of
https://github.com/servo/servo.git
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266 lines
7.8 KiB
Rust
266 lines
7.8 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#![deny(missing_docs)]
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//! Utilities for tracing JS-managed values.
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//!
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//! The lifetime of DOM objects is managed by the SpiderMonkey Garbage
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//! Collector. A rooted DOM object implementing the interface `Foo` is traced
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//! as follows:
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//!
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//! 1. The GC calls `_trace` defined in `FooBinding` during the marking
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//! phase. (This happens through `JSClass.trace` for non-proxy bindings, and
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//! through `ProxyTraps.trace` otherwise.)
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//! 2. `_trace` calls `Foo::trace()` (an implementation of `JSTraceable`).
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//! This is typically derived via a #[jstraceable] annotation
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//! 3. For all fields, `Foo::trace()`
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//! calls `trace()` on the field.
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//! For example, for fields of type `JS<T>`, `JS<T>::trace()` calls
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//! `trace_reflector()`.
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//! 4. `trace_reflector()` calls `trace_object()` with the `JSObject` for the
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//! reflector.
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//! 5. `trace_object()` calls `JS_CallTracer()` to notify the GC, which will
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//! add the object to the graph, and will trace that object as well.
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//!
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//! The no_jsmanaged_fields!() macro adds an empty implementation of JSTraceable to
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//! a datatype.
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use dom::bindings::js::JS;
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use dom::bindings::refcounted::Trusted;
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use dom::bindings::utils::{Reflectable, Reflector, WindowProxyHandler};
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use dom::node::{Node, TrustedNodeAddress};
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use script_task::ScriptChan;
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use collections::hash::{Hash, Hasher};
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use cssparser::RGBA;
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use geom::rect::Rect;
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use html5ever::tree_builder::QuirksMode;
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use hyper::header::Headers;
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use hyper::method::Method;
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use js::jsapi::{JSObject, JSTracer, JS_CallTracer, JSGCTraceKind};
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use js::jsval::JSVal;
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use js::rust::Cx;
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use layout_interface::{LayoutRPC, LayoutChan};
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use libc;
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use msg::constellation_msg::{PipelineId, SubpageId, WindowSizeData};
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use net::image_cache_task::ImageCacheTask;
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use script_traits::ScriptControlChan;
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use script_traits::UntrustedNodeAddress;
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use servo_msg::compositor_msg::ScriptListener;
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use servo_msg::constellation_msg::ConstellationChan;
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use servo_util::smallvec::{SmallVec1, SmallVec};
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use servo_util::str::{LengthOrPercentageOrAuto};
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use std::cell::{Cell, RefCell};
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use std::collections::HashMap;
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use std::comm::{Receiver, Sender};
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use std::io::timer::Timer;
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use std::rc::Rc;
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use string_cache::{Atom, Namespace};
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use style::PropertyDeclarationBlock;
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use url::Url;
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/// A trait to allow tracing (only) DOM objects.
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pub trait JSTraceable {
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/// Trace `self`.
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fn trace(&self, trc: *mut JSTracer);
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}
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impl<T: Reflectable> JSTraceable for JS<T> {
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fn trace(&self, trc: *mut JSTracer) {
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trace_reflector(trc, "", self.reflector());
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}
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}
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no_jsmanaged_fields!(Reflector)
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/// Trace a `JSVal`.
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pub fn trace_jsval(tracer: *mut JSTracer, description: &str, val: JSVal) {
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if !val.is_markable() {
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return;
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}
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unsafe {
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let name = description.to_c_str();
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(*tracer).debugPrinter = None;
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(*tracer).debugPrintIndex = -1;
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(*tracer).debugPrintArg = name.as_ptr() as *const libc::c_void;
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debug!("tracing value {}", description);
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JS_CallTracer(tracer, val.to_gcthing(), val.trace_kind());
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}
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}
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/// Trace the `JSObject` held by `reflector`.
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#[allow(unrooted_must_root)]
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pub fn trace_reflector(tracer: *mut JSTracer, description: &str, reflector: &Reflector) {
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trace_object(tracer, description, reflector.get_jsobject())
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}
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/// Trace a `JSObject`.
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pub fn trace_object(tracer: *mut JSTracer, description: &str, obj: *mut JSObject) {
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unsafe {
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let name = description.to_c_str();
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(*tracer).debugPrinter = None;
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(*tracer).debugPrintIndex = -1;
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(*tracer).debugPrintArg = name.as_ptr() as *const libc::c_void;
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debug!("tracing {}", description);
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JS_CallTracer(tracer, obj as *mut libc::c_void, JSGCTraceKind::JSTRACE_OBJECT);
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}
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}
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impl<T: JSTraceable> JSTraceable for RefCell<T> {
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fn trace(&self, trc: *mut JSTracer) {
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self.borrow().trace(trc)
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}
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}
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impl<T: JSTraceable> JSTraceable for Rc<T> {
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fn trace(&self, trc: *mut JSTracer) {
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(**self).trace(trc)
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}
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}
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impl<T: JSTraceable> JSTraceable for Box<T> {
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fn trace(&self, trc: *mut JSTracer) {
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(**self).trace(trc)
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}
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}
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impl<T: JSTraceable+Copy> JSTraceable for Cell<T> {
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fn trace(&self, trc: *mut JSTracer) {
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self.get().trace(trc)
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}
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}
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impl JSTraceable for *mut JSObject {
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fn trace(&self, trc: *mut JSTracer) {
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trace_object(trc, "object", *self);
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}
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}
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impl JSTraceable for JSVal {
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fn trace(&self, trc: *mut JSTracer) {
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trace_jsval(trc, "val", *self);
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}
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}
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// XXXManishearth Check if the following three are optimized to no-ops
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// if e.trace() is a no-op (e.g it is an no_jsmanaged_fields type)
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impl<T: JSTraceable> JSTraceable for Vec<T> {
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#[inline]
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fn trace(&self, trc: *mut JSTracer) {
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for e in self.iter() {
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e.trace(trc);
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}
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}
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}
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// XXXManishearth Check if the following three are optimized to no-ops
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// if e.trace() is a no-op (e.g it is an no_jsmanaged_fields type)
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impl<T: JSTraceable + 'static> JSTraceable for SmallVec1<T> {
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#[inline]
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fn trace(&self, trc: *mut JSTracer) {
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for e in self.iter() {
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e.trace(trc);
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}
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}
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}
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impl<T: JSTraceable> JSTraceable for Option<T> {
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#[inline]
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fn trace(&self, trc: *mut JSTracer) {
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self.as_ref().map(|e| e.trace(trc));
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}
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}
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impl<K,V,S,H> JSTraceable for HashMap<K, V, H> where K: Eq + Hash<S> + JSTraceable,
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V: JSTraceable,
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H: Hasher<S> {
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#[inline]
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fn trace(&self, trc: *mut JSTracer) {
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for e in self.iter() {
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e.val0().trace(trc);
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e.val1().trace(trc);
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}
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}
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}
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impl<A: JSTraceable, B: JSTraceable> JSTraceable for (A, B) {
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#[inline]
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fn trace(&self, trc: *mut JSTracer) {
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let (ref a, ref b) = *self;
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a.trace(trc);
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b.trace(trc);
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}
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}
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no_jsmanaged_fields!(bool, f32, f64, String, Url)
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no_jsmanaged_fields!(uint, u8, u16, u32, u64)
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no_jsmanaged_fields!(int, i8, i16, i32, i64)
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no_jsmanaged_fields!(Sender<T>)
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no_jsmanaged_fields!(Receiver<T>)
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no_jsmanaged_fields!(Rect<T>)
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no_jsmanaged_fields!(ImageCacheTask, ScriptControlChan)
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no_jsmanaged_fields!(Atom, Namespace, Timer)
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no_jsmanaged_fields!(Trusted<T>)
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no_jsmanaged_fields!(PropertyDeclarationBlock)
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// These three are interdependent, if you plan to put jsmanaged data
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// in one of these make sure it is propagated properly to containing structs
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no_jsmanaged_fields!(SubpageId, WindowSizeData, PipelineId)
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no_jsmanaged_fields!(QuirksMode)
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no_jsmanaged_fields!(Cx)
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no_jsmanaged_fields!(Headers, Method)
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no_jsmanaged_fields!(ConstellationChan)
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no_jsmanaged_fields!(LayoutChan)
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no_jsmanaged_fields!(WindowProxyHandler)
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no_jsmanaged_fields!(UntrustedNodeAddress)
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no_jsmanaged_fields!(LengthOrPercentageOrAuto)
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no_jsmanaged_fields!(RGBA)
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impl JSTraceable for Box<ScriptChan+Send> {
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#[inline]
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fn trace(&self, _trc: *mut JSTracer) {
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// Do nothing
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}
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}
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impl<'a> JSTraceable for &'a str {
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#[inline]
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fn trace(&self, _: *mut JSTracer) {
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// Do nothing
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}
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}
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impl<A,B> JSTraceable for fn(A) -> B {
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#[inline]
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fn trace(&self, _: *mut JSTracer) {
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// Do nothing
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}
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}
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impl JSTraceable for Box<ScriptListener+'static> {
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#[inline]
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fn trace(&self, _: *mut JSTracer) {
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// Do nothing
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}
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}
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impl JSTraceable for Box<LayoutRPC+'static> {
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#[inline]
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fn trace(&self, _: *mut JSTracer) {
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// Do nothing
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}
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}
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impl JSTraceable for TrustedNodeAddress {
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fn trace(&self, s: *mut JSTracer) {
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let TrustedNodeAddress(addr) = *self;
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let node = addr as *const Node;
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unsafe {
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JS::from_raw(node).trace(s)
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}
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}
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}
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