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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* 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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#ifndef mozilla_dom_IDTracker_h_
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#define mozilla_dom_IDTracker_h_
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#include "mozilla/Attributes.h"
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#include "mozilla/dom/Element.h"
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#include "nsAtom.h"
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#include "nsIDocument.h"
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#include "nsThreadUtils.h"
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class nsIURI;
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namespace mozilla {
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namespace dom {
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/**
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* Class to track what element is referenced by a given ID.
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*
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* To use it, call Reset() to set it up to watch a given URI. Call get()
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* anytime to determine the referenced element (which may be null if
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* the element isn't found). When the element changes, ElementChanged
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* will be called, so subclass this class if you want to receive that
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* notification. ElementChanged runs at safe-for-script time, i.e. outside
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* of the content update. Call Unlink() if you want to stop watching
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* for changes (get() will then return null).
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*
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* By default this is a single-shot tracker --- i.e., when ElementChanged
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* fires, we will automatically stop tracking. get() will continue to return
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* the changed-to element.
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* Override IsPersistent to return true if you want to keep tracking after
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* the first change.
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*/
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class IDTracker {
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public:
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typedef mozilla::dom::Element Element;
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IDTracker() : mReferencingImage(false) {}
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~IDTracker() { Unlink(); }
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/**
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* Find which element, if any, is referenced.
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*/
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Element* get() { return mElement; }
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/**
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* Set up the reference. This can be called multiple times to
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* change which reference is being tracked, but these changes
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* do not trigger ElementChanged.
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* @param aFrom the source element for context
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* @param aURI the URI containing a hash-reference to the element
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* @param aWatch if false, then we do not set up the notifications to track
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* changes, so ElementChanged won't fire and get() will always return the same
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* value, the current element for the ID.
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* @param aReferenceImage whether the ID references image elements which are
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* subject to the document's mozSetImageElement overriding mechanism.
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*/
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void Reset(nsIContent* aFrom, nsIURI* aURI, bool aWatch = true,
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bool aReferenceImage = false);
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/**
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* A variation on Reset() to set up a reference that consists of the ID of
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* an element in the same document as aFrom.
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* @param aFrom the source element for context
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* @param aID the ID of the element
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* @param aWatch if false, then we do not set up the notifications to track
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* changes, so ElementChanged won't fire and get() will always return the same
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* value, the current element for the ID.
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*/
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void ResetWithID(nsIContent* aFrom, const nsString& aID, bool aWatch = true);
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/**
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* Clears the reference. ElementChanged is not triggered. get() will return
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* null.
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*/
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void Unlink();
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void Traverse(nsCycleCollectionTraversalCallback* aCB);
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protected:
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/**
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* Override this to be notified of element changes. Don't forget
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* to call this superclass method to change mElement. This is called
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* at script-runnable time.
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*/
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virtual void ElementChanged(Element* aFrom, Element* aTo) { mElement = aTo; }
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/**
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* Override this to convert from a single-shot notification to
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* a persistent notification.
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*/
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virtual bool IsPersistent() { return false; }
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/**
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* Set ourselves up with our new document. Note that aDocument might be
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* null. Either aWatch must be false or aRef must be empty.
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*/
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void HaveNewDocument(nsIDocument* aDocument, bool aWatch,
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const nsString& aRef);
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private:
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static bool Observe(Element* aOldElement, Element* aNewElement, void* aData);
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class Notification : public nsISupports {
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public:
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virtual void SetTo(Element* aTo) = 0;
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virtual void Clear() { mTarget = nullptr; }
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virtual ~Notification() {}
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protected:
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explicit Notification(IDTracker* aTarget) : mTarget(aTarget) {
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NS_PRECONDITION(aTarget, "Must have a target");
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}
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IDTracker* mTarget;
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};
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class ChangeNotification : public mozilla::Runnable, public Notification {
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public:
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ChangeNotification(IDTracker* aTarget, Element* aFrom, Element* aTo)
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: mozilla::Runnable("IDTracker::ChangeNotification"),
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Notification(aTarget),
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mFrom(aFrom),
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mTo(aTo) {}
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// We need to actually declare all of nsISupports, because
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// Notification inherits from it but doesn't declare it.
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NS_DECL_ISUPPORTS_INHERITED
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NS_IMETHOD Run() override {
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if (mTarget) {
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mTarget->mPendingNotification = nullptr;
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mTarget->ElementChanged(mFrom, mTo);
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}
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return NS_OK;
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}
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virtual void SetTo(Element* aTo) override { mTo = aTo; }
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virtual void Clear() override {
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Notification::Clear();
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mFrom = nullptr;
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mTo = nullptr;
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}
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protected:
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virtual ~ChangeNotification() {}
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RefPtr<Element> mFrom;
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RefPtr<Element> mTo;
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};
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friend class ChangeNotification;
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class DocumentLoadNotification : public Notification, public nsIObserver {
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public:
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DocumentLoadNotification(IDTracker* aTarget, const nsString& aRef)
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: Notification(aTarget) {
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if (!mTarget->IsPersistent()) {
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mRef = aRef;
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}
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}
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NS_DECL_ISUPPORTS
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NS_DECL_NSIOBSERVER
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private:
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virtual ~DocumentLoadNotification() {}
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virtual void SetTo(Element* aTo) override {}
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nsString mRef;
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};
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friend class DocumentLoadNotification;
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RefPtr<nsAtom> mWatchID;
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nsCOMPtr<nsIDocument> mWatchDocument;
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RefPtr<Element> mElement;
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RefPtr<Notification> mPendingNotification;
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bool mReferencingImage;
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};
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inline void ImplCycleCollectionUnlink(IDTracker& aField) { aField.Unlink(); }
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inline void ImplCycleCollectionTraverse(
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nsCycleCollectionTraversalCallback& aCallback, IDTracker& aField,
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const char* aName, uint32_t aFlags = 0) {
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aField.Traverse(&aCallback);
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}
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} // namespace dom
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} // namespace mozilla
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#endif /* mozilla_dom_IDTracker_h_ */
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