Bug 1622322 - Improve print performance when sheets are adopted multiple times r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D68116

--HG--
extra : moz-landing-system : lando

dom/base/Document.cpp

@@ -12024,7 +12024,11 @@ void Document::FlushPendingLinkUpdates() {
 
 already_AddRefed<Document> Document::CreateStaticClone(
     nsIDocShell* aCloneContainer) {
+  MOZ_ASSERT(!mCreatingStaticClone);
+  MOZ_ASSERT(!GetProperty(nsGkAtoms::adoptedsheetclones));
   mCreatingStaticClone = true;
+  SetProperty(nsGkAtoms::adoptedsheetclones, new AdoptedStyleSheetCloneCache(),
+              nsINode::DeleteProperty<AdoptedStyleSheetCloneCache>);
 
   // Make document use different container during cloning.
   RefPtr<nsDocShell> originalShell = mDocumentContainer.get();
@@ -12094,6 +12098,7 @@ already_AddRefed<Document> Document::CreateStaticClone(
       clonedDoc->mPreloadReferrerInfo = clonedDoc->mReferrerInfo;
     }
   }
+  RemoveProperty(nsGkAtoms::adoptedsheetclones);
   mCreatingStaticClone = false;
   return clonedDoc.forget();
 }

dom/base/Document.h

@@ -488,6 +488,8 @@ class Document : public nsINode,
  public:
   typedef dom::ExternalResourceMap::ExternalResourceLoad ExternalResourceLoad;
   typedef dom::ReferrerPolicy ReferrerPolicyEnum;
+  using AdoptedStyleSheetCloneCache =
+      nsRefPtrHashtable<nsPtrHashKey<const StyleSheet>, StyleSheet>;
 
   // nsINode overrides the new operator for DOM Arena allocation.
   // to use the default one, we need to bring it back again
@@ -2810,7 +2812,7 @@ class Document : public nsINode,
    * Note that static documents are also "loaded as data" (if this method
    * returns true, IsLoadedAsData() will also return true).
    */
-  bool IsStaticDocument() { return mIsStaticDocument; }
+  bool IsStaticDocument() const { return mIsStaticDocument; }
 
   /**
    * Clones the document along with any subdocuments, stylesheet, etc.

dom/base/DocumentOrShadowRoot.cpp

@@ -199,18 +199,27 @@ void DocumentOrShadowRoot::ClearAdoptedStyleSheets() {
 }
 
 void DocumentOrShadowRoot::CloneAdoptedSheetsFrom(
-    DocumentOrShadowRoot& aSource) {
-  Document& ownerDoc = *AsNode().OwnerDoc();
+    const DocumentOrShadowRoot& aSource) {
+  if (!aSource.AdoptedSheetCount()) {
+    return;
+  }
   Sequence<OwningNonNull<StyleSheet>> list;
   if (!list.SetCapacity(mAdoptedStyleSheets.Length(), fallible)) {
     return;
   }
 
-  // TODO(nordzilla, bug 1621415) We can improve the performance here.
-  // https://bugzilla.mozilla.org/show_bug.cgi?id=1622322
-  for (auto& sheet : aSource.mAdoptedStyleSheets) {
-    DebugOnly<bool> succeeded =
-        list.AppendElement(sheet->CloneAdoptedSheet(ownerDoc), fallible);
+  Document& ownerDoc = *AsNode().OwnerDoc();
+  const Document& sourceDoc = *aSource.AsNode().OwnerDoc();
+  auto* clonedSheetMap = static_cast<Document::AdoptedStyleSheetCloneCache*>(
+      sourceDoc.GetProperty(nsGkAtoms::adoptedsheetclones));
+  MOZ_ASSERT(clonedSheetMap);
+
+  for (const StyleSheet* sheet : aSource.mAdoptedStyleSheets) {
+    RefPtr<StyleSheet> clone = clonedSheetMap->LookupForAdd(sheet).OrInsert(
+        [&] { return sheet->CloneAdoptedSheet(ownerDoc); });
+    MOZ_ASSERT(clone);
+    MOZ_DIAGNOSTIC_ASSERT(clone->ConstructorDocumentMatches(ownerDoc));
+    DebugOnly<bool> succeeded = list.AppendElement(std::move(clone), fallible);
     MOZ_ASSERT(succeeded);
   }
 

dom/base/DocumentOrShadowRoot.h

@@ -249,7 +249,7 @@ class DocumentOrShadowRoot {
    * Clone's the argument's adopted style sheets into this.
    * This should only be used when cloning a static document for printing.
    */
-  void CloneAdoptedSheetsFrom(DocumentOrShadowRoot&);
+  void CloneAdoptedSheetsFrom(const DocumentOrShadowRoot&);
 
   // Returns the reference to the sheet, if found in mStyleSheets.
   already_AddRefed<StyleSheet> RemoveSheet(StyleSheet& aSheet);

layout/base/tests/chrome/chrome.ini

@@ -26,6 +26,8 @@ support-files =
   test_document_adopted_styles_ref.html
   test_shadow_root_adopted_styles.html
   test_shadow_root_adopted_styles_ref.html
+  test_shared_adopted_styles.html
+  test_shared_adopted_styles_ref.html
   file_bug1018265.xhtml
 
 [test_bug396367-1.html]

layout/base/tests/chrome/printpreview_helper.xhtml

@@ -438,8 +438,14 @@ async function runTest13() {
   requestAnimationFrame(function() { setTimeout(runTest14); } );
 }
 
-// Crash test for bug 1615261
+// bug 1622322
 async function runTest14() {
+  await compareFiles("test_shared_adopted_styles.html", "test_shared_adopted_styles_ref.html");
+  requestAnimationFrame(function() { setTimeout(runTest15); } );
+}
+
+// Crash test for bug 1615261
+async function runTest15() {
   frameElts[0].contentDocument.body.innerHTML =
     '<style> div { width: 100px; height: 100px; background-image: url("animated.gif"); } </style>' +
     '<div>Firefox will crash if you try and print this page</div>';

layout/base/tests/chrome/test_shared_adopted_styles.html

@@ -0,0 +1,19 @@
+<!doctype html>
+<meta charset="utf-8">
+<body>
+  <div class="target"></div>
+  <span id="shadowHostA"></span>
+  <span id="shadowHostB"></span>
+</body>
+<script>
+  const sheet = new CSSStyleSheet();
+  sheet.replaceSync(".target { width: 100px; height: 100px; border-style: solid; border-color: blue; }");
+
+  const innerHTMLText = `<div class="target"></div>`
+  shadowHostA.attachShadow({mode: "open"}).innerHTML = innerHTMLText;
+  shadowHostB.attachShadow({mode: "open"}).innerHTML = innerHTMLText;
+
+  document.adoptedStyleSheets = [sheet];
+  shadowHostA.shadowRoot.adoptedStyleSheets = [sheet];
+  shadowHostB.shadowRoot.adoptedStyleSheets = [sheet];
+</script>

layout/base/tests/chrome/test_shared_adopted_styles_ref.html

@@ -0,0 +1,16 @@
+<!doctype html>
+<meta charset="utf-8">
+<body>
+  <div class="target"></div>
+  <span id="shadowHostA"></span>
+  <span id="shadowHostB"></span>
+  <style> .target { width: 100px; height: 100px; border-style: solid; border-color: blue; } </style>
+</body>
+<script>
+  const innerHTMLText = `
+    <div class="target"></div>
+    <style> .target { width: 100px; height: 100px; border-style: solid; border-color: blue; } </style>
+  `;
+  shadowHostA.attachShadow({mode: "open"}).innerHTML = innerHTMLText;
+  shadowHostB.attachShadow({mode: "open"}).innerHTML = innerHTMLText;
+</script>

layout/style/StyleSheet.h

@@ -412,7 +412,7 @@ class StyleSheet final : public nsICSSLoaderObserver, public nsWrapperCache {
   }
 
   // Ture if the sheet's constructor document matches the given document
-  bool ConstructorDocumentMatches(dom::Document& aDocument) const {
+  bool ConstructorDocumentMatches(const dom::Document& aDocument) const {
     return mConstructorDocument == &aDocument;
   }
 

xpcom/ds/StaticAtoms.py

@@ -69,6 +69,7 @@ STATIC_ATOMS = [
     Atom("activateontab", "activateontab"),
     Atom("actuate", "actuate"),
     Atom("address", "address"),
+    Atom("adoptedsheetclones", "adoptedsheetclones"),
     Atom("after", "after"),
     Atom("align", "align"),
     Atom("alink", "alink"),