1 files changed, 283 insertions, 0 deletions
diff --git a/dom/base/IDTracker.cpp b/dom/base/IDTracker.cpp
new file mode 100644
index 0000000000..4db592534d
--- /dev/null
+++ b/dom/base/IDTracker.cpp
@@ -0,0 +1,283 @@
+/* -*- 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/. */
+
+#include "IDTracker.h"
+
+#include "mozilla/Encoding.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/DocumentOrShadowRoot.h"
+#include "mozilla/dom/ShadowRoot.h"
+#include "nsAtom.h"
+#include "nsContentUtils.h"
+#include "nsIURI.h"
+#include "nsIReferrerInfo.h"
+#include "nsEscape.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsStringFwd.h"
+
+namespace mozilla::dom {
+
+static Element* LookupElement(DocumentOrShadowRoot& aDocOrShadow,
+                              const nsAString& aRef, bool aReferenceImage) {
+  if (aReferenceImage) {
+    return aDocOrShadow.LookupImageElement(aRef);
+  }
+  return aDocOrShadow.GetElementById(aRef);
+}
+
+static DocumentOrShadowRoot* FindTreeToWatch(nsIContent& aContent,
+                                             const nsAString& aID,
+                                             bool aReferenceImage) {
+  ShadowRoot* shadow = aContent.GetContainingShadow();
+
+  // We allow looking outside an <svg:use> shadow tree for backwards compat.
+  while (shadow && shadow->Host()->IsSVGElement(nsGkAtoms::use)) {
+    // <svg:use> shadow trees are immutable, so we can just early-out if we find
+    // our relevant element instead of having to support watching multiple
+    // trees.
+    if (LookupElement(*shadow, aID, aReferenceImage)) {
+      return shadow;
+    }
+    shadow = shadow->Host()->GetContainingShadow();
+  }
+
+  if (shadow) {
+    return shadow;
+  }
+
+  return aContent.OwnerDoc();
+}
+
+IDTracker::IDTracker() = default;
+
+IDTracker::~IDTracker() { Unlink(); }
+
+void IDTracker::ResetToURIFragmentID(nsIContent* aFromContent, nsIURI* aURI,
+                                     nsIReferrerInfo* aReferrerInfo,
+                                     bool aWatch, bool aReferenceImage) {
+  MOZ_ASSERT(aFromContent,
+             "ResetToURIFragmentID() expects non-null content pointer");
+
+  Unlink();
+
+  if (!aURI) return;
+
+  nsAutoCString refPart;
+  aURI->GetRef(refPart);
+  // Unescape %-escapes in the reference. The result will be in the
+  // document charset, hopefully...
+  NS_UnescapeURL(refPart);
+
+  // Get the thing to observe changes to.
+  Document* doc = aFromContent->OwnerDoc();
+  auto encoding = doc->GetDocumentCharacterSet();
+
+  nsAutoString ref;
+  nsresult rv = encoding->DecodeWithoutBOMHandling(refPart, ref);
+  if (NS_FAILED(rv) || ref.IsEmpty()) {
+    return;
+  }
+
+  if (aFromContent->IsInNativeAnonymousSubtree()) {
+    // This happens, for example, if aFromContent is part of the content
+    // inserted by a call to Document::InsertAnonymousContent, which we
+    // also want to handle.  (It also happens for other native anonymous content
+    // etc.)
+    Element* anonRoot =
+        doc->GetAnonRootIfInAnonymousContentContainer(aFromContent);
+    if (anonRoot) {
+      mElement = nsContentUtils::MatchElementId(anonRoot, ref);
+      // We don't have watching working yet for anonymous content, so bail out
+      // here.
+      return;
+    }
+  }
+
+  bool isEqualExceptRef;
+  rv = aURI->EqualsExceptRef(doc->GetDocumentURI(), &isEqualExceptRef);
+  DocumentOrShadowRoot* docOrShadow;
+  if (NS_FAILED(rv) || !isEqualExceptRef) {
+    RefPtr<Document::ExternalResourceLoad> load;
+    doc = doc->RequestExternalResource(aURI, aReferrerInfo, aFromContent,
+                                       getter_AddRefs(load));
+    docOrShadow = doc;
+    if (!doc) {
+      if (!load || !aWatch) {
+        // Nothing will ever happen here
+        return;
+      }
+
+      DocumentLoadNotification* observer =
+          new DocumentLoadNotification(this, ref);
+      mPendingNotification = observer;
+      load->AddObserver(observer);
+      // Keep going so we set up our watching stuff a bit
+    }
+  } else {
+    docOrShadow = FindTreeToWatch(*aFromContent, ref, aReferenceImage);
+  }
+
+  if (aWatch) {
+    mWatchID = NS_Atomize(ref);
+  }
+
+  mReferencingImage = aReferenceImage;
+  HaveNewDocumentOrShadowRoot(docOrShadow, aWatch, ref);
+}
+
+void IDTracker::ResetWithLocalRef(Element& aFrom, const nsAString& aLocalRef,
+                                  bool aWatch) {
+  MOZ_ASSERT(nsContentUtils::IsLocalRefURL(aLocalRef));
+
+  nsAutoCString ref;
+  if (!AppendUTF16toUTF8(Substring(aLocalRef, 1), ref, mozilla::fallible)) {
+    Unlink();
+    return;
+  }
+  NS_UnescapeURL(ref);
+  RefPtr<nsAtom> idAtom = NS_Atomize(ref);
+  ResetWithID(aFrom, idAtom, aWatch);
+}
+
+void IDTracker::ResetWithID(Element& aFrom, nsAtom* aID, bool aWatch) {
+  MOZ_ASSERT(aID);
+
+  Unlink();
+
+  if (aID->IsEmpty()) {
+    return;
+  }
+
+  if (aWatch) {
+    mWatchID = aID;
+  }
+
+  mReferencingImage = false;
+
+  nsDependentAtomString str(aID);
+  DocumentOrShadowRoot* docOrShadow =
+      FindTreeToWatch(aFrom, str, /* aReferenceImage = */ false);
+  HaveNewDocumentOrShadowRoot(docOrShadow, aWatch, str);
+}
+
+void IDTracker::HaveNewDocumentOrShadowRoot(DocumentOrShadowRoot* aDocOrShadow,
+                                            bool aWatch, const nsString& aRef) {
+  if (aWatch) {
+    mWatchDocumentOrShadowRoot = nullptr;
+    if (aDocOrShadow) {
+      mWatchDocumentOrShadowRoot = &aDocOrShadow->AsNode();
+      mElement = aDocOrShadow->AddIDTargetObserver(mWatchID, Observe, this,
+                                                   mReferencingImage);
+    }
+    return;
+  }
+
+  if (!aDocOrShadow) {
+    return;
+  }
+
+  if (Element* e = LookupElement(*aDocOrShadow, aRef, mReferencingImage)) {
+    mElement = e;
+  }
+}
+
+void IDTracker::Traverse(nsCycleCollectionTraversalCallback* aCB) {
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(*aCB, "mWatchDocumentOrShadowRoot");
+  aCB->NoteXPCOMChild(mWatchDocumentOrShadowRoot);
+  NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(*aCB, "mElement");
+  aCB->NoteXPCOMChild(mElement);
+}
+
+void IDTracker::Unlink() {
+  if (mWatchID) {
+    if (DocumentOrShadowRoot* docOrShadow = GetWatchDocOrShadowRoot()) {
+      docOrShadow->RemoveIDTargetObserver(mWatchID, Observe, this,
+                                          mReferencingImage);
+    }
+  }
+  if (mPendingNotification) {
+    mPendingNotification->Clear();
+    mPendingNotification = nullptr;
+  }
+  mWatchDocumentOrShadowRoot = nullptr;
+  mWatchID = nullptr;
+  mElement = nullptr;
+  mReferencingImage = false;
+}
+
+void IDTracker::ElementChanged(Element* aFrom, Element* aTo) { mElement = aTo; }
+
+bool IDTracker::Observe(Element* aOldElement, Element* aNewElement,
+                        void* aData) {
+  IDTracker* p = static_cast<IDTracker*>(aData);
+  if (p->mPendingNotification) {
+    p->mPendingNotification->SetTo(aNewElement);
+  } else {
+    NS_ASSERTION(aOldElement == p->mElement, "Failed to track content!");
+    ChangeNotification* watcher =
+        new ChangeNotification(p, aOldElement, aNewElement);
+    p->mPendingNotification = watcher;
+    nsContentUtils::AddScriptRunner(watcher);
+  }
+  bool keepTracking = p->IsPersistent();
+  if (!keepTracking) {
+    p->mWatchDocumentOrShadowRoot = nullptr;
+    p->mWatchID = nullptr;
+  }
+  return keepTracking;
+}
+
+IDTracker::ChangeNotification::ChangeNotification(IDTracker* aTarget,
+                                                  Element* aFrom, Element* aTo)
+    : mozilla::Runnable("IDTracker::ChangeNotification"),
+      Notification(aTarget),
+      mFrom(aFrom),
+      mTo(aTo) {}
+
+IDTracker::ChangeNotification::~ChangeNotification() = default;
+
+void IDTracker::ChangeNotification::SetTo(Element* aTo) { mTo = aTo; }
+
+void IDTracker::ChangeNotification::Clear() {
+  Notification::Clear();
+  mFrom = nullptr;
+  mTo = nullptr;
+}
+
+NS_IMPL_ISUPPORTS_INHERITED0(IDTracker::ChangeNotification, mozilla::Runnable)
+NS_IMPL_ISUPPORTS(IDTracker::DocumentLoadNotification, nsIObserver)
+
+NS_IMETHODIMP
+IDTracker::DocumentLoadNotification::Observe(nsISupports* aSubject,
+                                             const char* aTopic,
+                                             const char16_t* aData) {
+  NS_ASSERTION(!strcmp(aTopic, "external-resource-document-created"),
+               "Unexpected topic");
+  if (mTarget) {
+    nsCOMPtr<Document> doc = do_QueryInterface(aSubject);
+    mTarget->mPendingNotification = nullptr;
+    NS_ASSERTION(!mTarget->mElement, "Why do we have content here?");
+    // If we got here, that means we had Reset*() called with
+    // aWatch == true.  So keep watching if IsPersistent().
+    mTarget->HaveNewDocumentOrShadowRoot(doc, mTarget->IsPersistent(), mRef);
+    mTarget->ElementChanged(nullptr, mTarget->mElement);
+  }
+  return NS_OK;
+}
+
+DocumentOrShadowRoot* IDTracker::GetWatchDocOrShadowRoot() const {
+  if (!mWatchDocumentOrShadowRoot) {
+    return nullptr;
+  }
+  MOZ_ASSERT(mWatchDocumentOrShadowRoot->IsDocument() ||
+             mWatchDocumentOrShadowRoot->IsShadowRoot());
+  if (ShadowRoot* shadow = ShadowRoot::FromNode(*mWatchDocumentOrShadowRoot)) {
+    return shadow;
+  }
+  return mWatchDocumentOrShadowRoot->AsDocument();
+}
+
+}  // namespace mozilla::dom