/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */
#ifndef mozilla_dom_IDTracker_h_
#define mozilla_dom_IDTracker_h_
#include "mozilla/Attributes.h"
#include "nsIObserver.h"
#include "nsThreadUtils.h"
class nsAtom;
class nsIContent;
class nsINode;
class nsIURI;
class nsIReferrerInfo;
namespace mozilla::dom {
class Document;
class DocumentOrShadowRoot;
class Element;
/**
* Class to track what element is referenced by a given ID.
*
* To use it, call one of the Reset methods to set it up to watch a given ID.
* Call get() anytime to determine the referenced element (which may be null if
* the element isn't found). When the element changes, ElementChanged
* will be called, so subclass this class if you want to receive that
* notification. ElementChanged runs at safe-for-script time, i.e. outside
* of the content update. Call Unlink() if you want to stop watching
* for changes (get() will then return null).
*
* By default this is a single-shot tracker --- i.e., when ElementChanged
* fires, we will automatically stop tracking. get() will continue to return
* the changed-to element.
* Override IsPersistent to return true if you want to keep tracking after
* the first change.
*/
class IDTracker {
public:
using Element = mozilla::dom::Element;
IDTracker();
~IDTracker();
/**
* Find which element, if any, is referenced.
*/
Element* get() {
return mElement; }
/**
* Set up a reference to another element, identified by the fragment
* identifier in aURI. If aURI identifies an element in a document that is
* not aFrom's document, then an ExternalResourceLoad object will be created
* to load and store that document in the background as a resource document
* (until we, and any other observers, no longer observe it).
*
* This can be called multiple times with different URIs to change which
* element is being tracked, but these changes do not trigger ElementChanged.
*
* @param aFrom The source element that has made the reference to aURI.
* @param aURI A URI containing a fragment identifier that identifies the
* target element.
* @param aReferrerInfo The referrerInfo for the source element. Needed if
* the referenced element is in an external resource document.
* @param aReferenceImage Whether the reference comes from a -moz-element
* property (that is, we're creating a reference an "image element", which
* is subject to the document's mozSetImageElement overriding mechanism).
*/
void ResetToURIWithFragmentID(nsIContent* aFrom, nsIURI* aURI,
nsIReferrerInfo* aReferrerInfo,
bool aReferenceImage =
false);
/**
* A variation on ResetToURIWithFragmentID() to set up a reference that
* consists only of a fragment identifier, referencing an element in the same
* document as aFrom.
*
* @param aFrom The source element that is making the reference.
* @param aLocalRef The fragment identifier that identifies the target
* element. Must begin with "#".
*/
void ResetToLocalFragmentID(Element& aFrom,
const nsAString& aLocalRef);
/**
* A variation on ResetToURIWithFragmentID() to set up a reference that
* consists of a pre-parsed ID, referencing an element in the same document
* as aFrom.
*
* @param aFrom The source element that is making the reference.
* @param aID The ID of the target element.
*/
void ResetToID(Element& aFrom, nsAtom* aID);
/**
* Clears the reference. ElementChanged is not triggered. get() will return
* null.
*/
void Unlink();
void Traverse(nsCycleCollectionTraversalCallback* aCB);
protected:
/**
* Override this to be notified of element changes. Don't forget
* to call this superclass method to change mElement. This is called
* at script-runnable time.
*/
virtual void ElementChanged(Element* aFrom, Element* aTo);
/**
* Override this to convert from a single-shot notification to
* a persistent notification.
*/
virtual bool IsPersistent() {
return false; }
/**
* Set ourselves up with our new document. Note that aDocument might be
* null. Either aWatch must be false or aRef must be empty.
*/
void HaveNewDocumentOrShadowRoot(DocumentOrShadowRoot*,
bool aWatch,
const nsString& aRef);
private:
static bool Observe(Element* aOldElement, Element* aNewElement,
void* aData);
class Notification :
public nsISupports {
public:
virtual void SetTo(Element* aTo) = 0;
virtual void Clear() { mTarget = nullptr; }
virtual ~Notification() =
default;
protected:
explicit Notification(IDTracker* aTarget) : mTarget(aTarget) {
MOZ_ASSERT(aTarget,
"Must have a target");
}
IDTracker* mTarget;
};
class ChangeNotification :
public mozilla::Runnable,
public Notification {
public:
ChangeNotification(IDTracker* aTarget, Element* aFrom, Element* aTo);
// We need to actually declare all of nsISupports, because
// Notification inherits from it but doesn't declare it.
NS_DECL_ISUPPORTS_INHERITED
NS_IMETHOD Run() override {
if (mTarget) {
mTarget->mPendingNotification = nullptr;
mTarget->ElementChanged(mFrom, mTo);
}
return NS_OK;
}
void SetTo(Element* aTo) override;
void Clear() override;
protected:
virtual ~ChangeNotification();
RefPtr<Element> mFrom;
RefPtr<Element> mTo;
};
friend class ChangeNotification;
class DocumentLoadNotification :
public Notification,
public nsIObserver {
public:
DocumentLoadNotification(IDTracker* aTarget,
const nsString& aRef)
: Notification(aTarget) {
if (!mTarget->IsPersistent()) {
mRef = aRef;
}
}
NS_DECL_ISUPPORTS
NS_DECL_NSIOBSERVER
private:
virtual ~DocumentLoadNotification() =
default;
virtual void SetTo(Element* aTo) override {}
nsString mRef;
};
friend class DocumentLoadNotification;
DocumentOrShadowRoot* GetWatchDocOrShadowRoot()
const;
RefPtr<nsAtom> mWatchID;
nsCOMPtr<nsINode>
mWatchDocumentOrShadowRoot;
// Always a `DocumentOrShadowRoot`.
RefPtr<Element> mElement;
RefPtr<Notification> mPendingNotification;
bool mReferencingImage =
false;
};
inline void ImplCycleCollectionUnlink(IDTracker& aField) { aField.Unlink(); }
inline void ImplCycleCollectionTraverse(
nsCycleCollectionTraversalCallback& aCallback, IDTracker& aField,
const char* aName, uint32_t aFlags = 0) {
aField.Traverse(&aCallback);
}
}
// namespace mozilla::dom
#endif /* mozilla_dom_IDTracker_h_ */
