[IntersectionObserver] Allow Document argument to constructor

This implements a behavioral change as described in:

https://github.com/w3c/IntersectionObserver/issues/372

If the 'root' argument to the IntersectionObserver constructor is a
Document, then the observer will clip to the Document's root
scroller. For the top Document, this is the same behavior as the
implicit root. For an iframe Document, this is new behavior which is
unobtainable by other means.

BUG=1015183

Change-Id: I234bfce28ab954bb15b8d157bc22ee2d2469d5e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2003750Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734268}

third_party/blink/renderer/bindings/core/v8/generated.gni

@@ -40,6 +40,8 @@ bindings_core_generated_union_type_files = [
   "$bindings_core_v8_output_dir/double_or_string.h",
   "$bindings_core_v8_output_dir/double_or_string_or_string_sequence.cc",
   "$bindings_core_v8_output_dir/double_or_string_or_string_sequence.h",
+  "$bindings_core_v8_output_dir/element_or_document.cc",
+  "$bindings_core_v8_output_dir/element_or_document.h",
   "$bindings_core_v8_output_dir/event_listener_options_or_boolean.cc",
   "$bindings_core_v8_output_dir/event_listener_options_or_boolean.h",
   "$bindings_core_v8_output_dir/file_or_usv_string.cc",

third_party/blink/renderer/core/dom/document.cc

@@ -226,6 +226,7 @@
 #include "third_party/blink/renderer/core/inspector/console_message.h"
 #include "third_party/blink/renderer/core/inspector/inspector_trace_events.h"
 #include "third_party/blink/renderer/core/inspector/main_thread_debugger.h"
+#include "third_party/blink/renderer/core/intersection_observer/element_intersection_observer_data.h"
 #include "third_party/blink/renderer/core/intersection_observer/intersection_observer_controller.h"
 #include "third_party/blink/renderer/core/intersection_observer/intersection_observer_entry.h"
 #include "third_party/blink/renderer/core/layout/adjust_for_absolute_zoom.h"
@@ -6839,6 +6840,20 @@ Document::EnsureIntersectionObserverController() {
   return *intersection_observer_controller_;
 }
 
+ElementIntersectionObserverData*
+Document::DocumentExplicitRootIntersectionObserverData() const {
+  return document_explicit_root_intersection_observer_data_.Get();
+}
+
+ElementIntersectionObserverData&
+Document::EnsureDocumentExplicitRootIntersectionObserverData() {
+  if (!document_explicit_root_intersection_observer_data_) {
+    document_explicit_root_intersection_observer_data_ =
+        MakeGarbageCollected<ElementIntersectionObserverData>();
+  }
+  return *document_explicit_root_intersection_observer_data_;
+}
+
 ResizeObserverController& Document::EnsureResizeObserverController() {
   if (!resize_observer_controller_) {
     resize_observer_controller_ =
@@ -7824,6 +7839,7 @@ void Document::Trace(Visitor* visitor) {
   visitor->Trace(elem_sheet_);
   visitor->Trace(node_iterators_);
   visitor->Trace(ranges_);
+  visitor->Trace(document_explicit_root_intersection_observer_data_);
   visitor->Trace(style_engine_);
   visitor->Trace(form_controller_);
   visitor->Trace(visited_link_state_);

third_party/blink/renderer/core/dom/document.h

@@ -98,6 +98,7 @@ class CanvasFontCache;
 class ChromeClient;
 class Comment;
 class ComputedAccessibleNode;
+class ElementIntersectionObserverData;
 class WindowAgent;
 class WindowAgentFactory;
 class ComputedStyle;
@@ -954,6 +955,14 @@ class CORE_EXPORT Document : public ContainerNode,
   IntersectionObserverController* GetIntersectionObserverController();
   IntersectionObserverController& EnsureIntersectionObserverController();
 
+  // This is used to track IntersectionObservers for which this document is the
+  // explicit root. The IntersectionObserverController tracks *all* observers
+  // associated with this document; usually that's what you want.
+  ElementIntersectionObserverData*
+  DocumentExplicitRootIntersectionObserverData() const;
+  ElementIntersectionObserverData&
+  EnsureDocumentExplicitRootIntersectionObserverData();
+
   ResizeObserverController* GetResizeObserverController() const {
     return resize_observer_controller_;
   }
@@ -1886,6 +1895,9 @@ class CORE_EXPORT Document : public ContainerNode,
 
   MutationObserverOptions mutation_observer_types_;
 
+  Member<ElementIntersectionObserverData>
+      document_explicit_root_intersection_observer_data_;
+
   Member<StyleEngine> style_engine_;
   Member<StyleSheetList> style_sheet_list_;
 

third_party/blink/renderer/core/intersection_observer/intersection_geometry.cc

@@ -188,29 +188,29 @@ IntersectionGeometry::RootGeometry::RootGeometry(const LayoutObject* root,
   root_to_document_transform = transform_state.AccumulatedTransform();
 }
 
-// If root_element is non-null, it is treated as the explicit root of an
+// If root_node is non-null, it is treated as the explicit root of an
 // IntersectionObserver; if it is valid, its LayoutObject is returned.
 //
-// If root_element is null, returns the object to be used as the implicit root
+// If root_node is null, returns the object to be used as the implicit root
 // for a given target.
 //
 //   https://w3c.github.io/IntersectionObserver/#dom-intersectionobserver-root
 const LayoutObject* IntersectionGeometry::GetRootLayoutObjectForTarget(
-    const Element* root_element,
+    const Node* root_node,
     LayoutObject* target,
     bool check_containing_block_chain) {
-  if (!root_element)
+  if (!root_node)
     return target ? LocalRootView(*target) : nullptr;
-  if (!root_element->isConnected())
+  if (!root_node->isConnected())
     return nullptr;
 
   LayoutObject* root = nullptr;
   if (RuntimeEnabledFeatures::
           IntersectionObserverDocumentScrollingElementRootEnabled() &&
-      root_element == root_element->GetDocument().scrollingElement()) {
-    root = root_element->GetDocument().GetLayoutView();
+      root_node->IsDocumentNode()) {
+    root = To<Document>(root_node)->GetLayoutView();
   } else {
-    root = root_element->GetLayoutObject();
+    root = root_node->GetLayoutObject();
     if (target && check_containing_block_chain &&
         !IsContainingBlockChainDescendant(target, root)) {
       root = nullptr;
@@ -219,7 +219,7 @@ const LayoutObject* IntersectionGeometry::GetRootLayoutObjectForTarget(
   return root;
 }
 
-IntersectionGeometry::IntersectionGeometry(const Element* root_element,
+IntersectionGeometry::IntersectionGeometry(const Node* root_node,
                                            const Element& target_element,
                                            const Vector<Length>& root_margin,
                                            const Vector<float>& thresholds,
@@ -230,13 +230,13 @@ IntersectionGeometry::IntersectionGeometry(const Element* root_element,
       threshold_index_(0) {
   if (cached_rects)
     cached_rects->valid = false;
-  if (!root_element)
+  if (!root_node)
     flags_ |= kRootIsImplicit;
   LayoutObject* target = GetTargetLayoutObject(target_element);
   if (!target)
     return;
-  const LayoutObject* root = GetRootLayoutObjectForTarget(
-      root_element, target, !ShouldUseCachedRects());
+  const LayoutObject* root =
+      GetRootLayoutObjectForTarget(root_node, target, !ShouldUseCachedRects());
   if (!root)
     return;
   RootGeometry root_geometry(root, root_margin);
@@ -244,7 +244,7 @@ IntersectionGeometry::IntersectionGeometry(const Element* root_element,
 }
 
 IntersectionGeometry::IntersectionGeometry(const RootGeometry& root_geometry,
-                                           const Element& explicit_root,
+                                           const Node& explicit_root,
                                            const Element& target_element,
                                            const Vector<float>& thresholds,
                                            unsigned flags,

third_party/blink/renderer/core/intersection_observer/intersection_geometry.h

@@ -17,8 +17,9 @@ namespace blink {
 
 class Element;
 class LayoutObject;
+class Node;
 
-// Computes the intersection between an ancestor (root) element and a
+// Computes the intersection between an ancestor (root) node and a
 // descendant (target) element, with overflow and CSS clipping applied.
 // Optionally also checks whether the target is occluded or has visual
 // effects applied.
@@ -67,11 +68,11 @@ class CORE_EXPORT IntersectionGeometry {
   };
 
   static const LayoutObject* GetRootLayoutObjectForTarget(
-      const Element* root_element,
+      const Node* root_node,
       LayoutObject* target,
       bool check_containing_block_chain);
 
-  IntersectionGeometry(const Element* root,
+  IntersectionGeometry(const Node* root,
                        const Element& target,
                        const Vector<Length>& root_margin,
                        const Vector<float>& thresholds,
@@ -79,7 +80,7 @@ class CORE_EXPORT IntersectionGeometry {
                        CachedRects* cached_rects = nullptr);
 
   IntersectionGeometry(const RootGeometry& root_geometry,
-                       const Element& explicit_root,
+                       const Node& explicit_root,
                        const Element& target,
                        const Vector<float>& thresholds,
                        unsigned flags,

third_party/blink/renderer/core/intersection_observer/intersection_observer.cc

@@ -160,7 +160,12 @@ IntersectionObserver* IntersectionObserver::Create(
     const IntersectionObserverInit* observer_init,
     IntersectionObserverDelegate& delegate,
     ExceptionState& exception_state) {
-  Element* root = observer_init->root();
+  Node* root = nullptr;
+  if (observer_init->root().IsElement()) {
+    root = observer_init->root().GetAsElement();
+  } else if (observer_init->root().IsDocument()) {
+    root = observer_init->root().GetAsDocument();
+  }
 
   DOMHighResTimeStamp delay = 0;
   bool track_visibility = false;
@@ -231,7 +236,7 @@ IntersectionObserver* IntersectionObserver::Create(
 
 IntersectionObserver::IntersectionObserver(
     IntersectionObserverDelegate& delegate,
-    Element* root,
+    Node* root,
     const Vector<Length>& root_margin,
     const Vector<float>& thresholds,
     ThresholdInterpretation semantics,
@@ -277,7 +282,14 @@ IntersectionObserver::IntersectionObserver(
       break;
   }
   if (root) {
-    root->EnsureIntersectionObserverData().AddObserver(*this);
+    if (root->IsDocumentNode()) {
+      To<Document>(root)
+          ->EnsureDocumentExplicitRootIntersectionObserverData()
+          .AddObserver(*this);
+    } else {
+      DCHECK(root->IsElementNode());
+      To<Element>(root)->EnsureIntersectionObserverData().AddObserver(*this);
+    }
     root->GetDocument()
         .EnsureIntersectionObserverController()
         .AddTrackedObserver(*this, track_visibility);

third_party/blink/renderer/core/intersection_observer/intersection_observer.h

@@ -24,6 +24,7 @@ class ExceptionState;
 class IntersectionObserverDelegate;
 class IntersectionObserverEntry;
 class IntersectionObserverInit;
+class Node;
 class ScriptState;
 class V8IntersectionObserverCallback;
 
@@ -98,7 +99,7 @@ class CORE_EXPORT IntersectionObserver final
   static void ResumeSuspendedObservers();
 
   explicit IntersectionObserver(IntersectionObserverDelegate&,
-                                Element*,
+                                Node*,
                                 const Vector<Length>& root_margin,
                                 const Vector<float>& thresholds,
                                 ThresholdInterpretation semantics,
@@ -114,14 +115,14 @@ class CORE_EXPORT IntersectionObserver final
       ExceptionState& = ASSERT_NO_EXCEPTION);
 
   // API attributes.
-  Element* root() const { return root_.Get(); }
+  Node* root() const { return root_.Get(); }
   String rootMargin() const;
   const Vector<float>& thresholds() const { return thresholds_; }
   DOMHighResTimeStamp delay() const { return delay_; }
   bool trackVisibility() const { return track_visibility_; }
   bool trackFractionOfRoot() const { return track_fraction_of_root_; }
 
-  // An observer can either track intersections with an explicit root Element,
+  // An observer can either track intersections with an explicit root Node,
   // or with the the top-level frame's viewport (the "implicit root").  When
   // tracking the implicit root, root_ will be null, but because root_ is a
   // weak pointer, we cannot surmise that this observer tracks the implicit
@@ -147,7 +148,7 @@ class CORE_EXPORT IntersectionObserver final
   DeliveryBehavior GetDeliveryBehavior() const;
   void Deliver();
 
-  // Returns false if this observer has an explicit root element which has been
+  // Returns false if this observer has an explicit root node which has been
   // deleted; true otherwise.
   bool RootIsValid() const;
   bool CanUseCachedRects() const { return can_use_cached_rects_; }
@@ -166,7 +167,7 @@ class CORE_EXPORT IntersectionObserver final
   void ProcessCustomWeakness(const WeakCallbackInfo&);
 
   const Member<IntersectionObserverDelegate> delegate_;
-  UntracedMember<Element> root_;
+  UntracedMember<Node> root_;
   HeapLinkedHashSet<WeakMember<IntersectionObservation>> observations_;
   Vector<float> thresholds_;
   DOMHighResTimeStamp delay_;

third_party/blink/renderer/core/intersection_observer/intersection_observer.idl

@@ -10,8 +10,8 @@ callback IntersectionObserverCallback = void (sequence<IntersectionObserverEntry
     Exposed=Window,
     ActiveScriptWrappable
 ] interface IntersectionObserver {
-    [CallWith=ScriptState, RaisesException, MeasureAs=IntersectionObserver_Constructor] constructor(IntersectionObserverCallback callback, optional IntersectionObserverInit options = {});
-    readonly attribute Element? root;
+    [CallWith=ScriptState, RaisesException, MeasureAs=IntersectionObserver_Constructor] constructor(IntersectionObserverCallback callback, optional IntersectionObserverInit options);
+    readonly attribute Node? root;
     readonly attribute DOMString rootMargin;
     // https://github.com/WICG/IntersectionObserver/issues/114
     readonly attribute FrozenArray<double> thresholds;

third_party/blink/renderer/core/intersection_observer/intersection_observer_controller.h

@@ -54,6 +54,7 @@ class IntersectionObserverController
   const char* NameInHeapSnapshot() const override {
     return "IntersectionObserverController";
   }
+
   unsigned GetTrackedObserverCountForTesting() const {
     return explicit_root_observers_.size();
   }
@@ -72,7 +73,7 @@ class IntersectionObserverController
   // IntersectionObservers for which this is the execution context of the
   // callback, and with unsent notifications.
   HeapHashSet<Member<IntersectionObserver>> pending_intersection_observers_;
-  // This is 'true' if any tracked element is the target of an observer for
+  // This is 'true' if any tracked node is the target of an observer for
   // which observer->trackVisibility() is true.
   bool needs_occlusion_tracking_;
 };

third_party/blink/renderer/core/intersection_observer/intersection_observer_init.idl

@@ -5,7 +5,7 @@
 // https://wicg.github.io/IntersectionObserver/#intersection-observer-init
 
 dictionary IntersectionObserverInit {
-    Element? root = null;
+    (Element or Document)? root = null;
     DOMString rootMargin = "0px";
     (double or sequence<double>) threshold = 0;
     [RuntimeEnabled=IntersectionObserverV2] DOMHighResTimeStamp delay = 0;

third_party/blink/renderer/core/intersection_observer/intersection_observer_test.cc

@@ -13,6 +13,7 @@
 #include "third_party/blink/renderer/core/dom/element.h"
 #include "third_party/blink/renderer/core/exported/web_view_impl.h"
 #include "third_party/blink/renderer/core/frame/local_frame_view.h"
+#include "third_party/blink/renderer/core/frame/web_local_frame_impl.h"
 #include "third_party/blink/renderer/core/intersection_observer/element_intersection_observer_data.h"
 #include "third_party/blink/renderer/core/intersection_observer/intersection_observer_controller.h"
 #include "third_party/blink/renderer/core/intersection_observer/intersection_observer_delegate.h"
@@ -132,7 +133,7 @@ TEST_F(IntersectionObserverTest, NotificationSentWhenRootRemoved) {
   Element* root = GetDocument().getElementById("root");
   ASSERT_TRUE(root);
   IntersectionObserverInit* observer_init = IntersectionObserverInit::Create();
-  observer_init->setRoot(root);
+  observer_init->setRoot(ElementOrDocument::FromElement(root));
   DummyExceptionStateForTesting exception_state;
   TestIntersectionObserverDelegate* observer_delegate =
       MakeGarbageCollected<TestIntersectionObserverDelegate>(GetDocument());
@@ -159,27 +160,32 @@ TEST_F(IntersectionObserverTest, NotificationSentWhenRootRemoved) {
   EXPECT_FALSE(observer_delegate->LastEntry()->isIntersecting());
 }
 
-TEST_F(IntersectionObserverTest, ScrollingElementRootClips) {
+TEST_F(IntersectionObserverTest, DocumentRootClips) {
   ScopedIntersectionObserverDocumentScrollingElementRootForTest scope(true);
   WebView().MainFrameWidget()->Resize(WebSize(800, 600));
   SimRequest main_resource("https://example.com/", "text/html");
+  SimRequest iframe_resource("https://example.com/iframe.html", "text/html");
   LoadURL("https://example.com/");
   main_resource.Complete(R"HTML(
+    <iframe src="iframe.html" style="width:200px; height:100px"></iframe>
+  )HTML");
+  iframe_resource.Complete(R"HTML(
     <div id='target'>Hello, world!</div>
     <div id='spacer' style='height:2000px'></div>
   )HTML");
 
-  Element* root = GetDocument().scrollingElement();
-  ASSERT_TRUE(root);
+  Document* iframe_document = To<WebLocalFrameImpl>(MainFrame().FirstChild())
+                                  ->GetFrame()
+                                  ->GetDocument();
   IntersectionObserverInit* observer_init = IntersectionObserverInit::Create();
-  observer_init->setRoot(root);
+  observer_init->setRoot(ElementOrDocument::FromDocument(iframe_document));
   DummyExceptionStateForTesting exception_state;
   TestIntersectionObserverDelegate* observer_delegate =
       MakeGarbageCollected<TestIntersectionObserverDelegate>(GetDocument());
   IntersectionObserver* observer = IntersectionObserver::Create(
       observer_init, *observer_delegate, exception_state);
   ASSERT_FALSE(exception_state.HadException());
-  Element* target = GetDocument().getElementById("target");
+  Element* target = iframe_document->getElementById("target");
   ASSERT_TRUE(target);
   observer->observe(target, exception_state);
 
@@ -190,8 +196,8 @@ TEST_F(IntersectionObserverTest, ScrollingElementRootClips) {
   EXPECT_EQ(observer_delegate->EntryCount(), 1);
   EXPECT_TRUE(observer_delegate->LastEntry()->isIntersecting());
 
-  GetDocument().View()->LayoutViewport()->SetScrollOffset(ScrollOffset(0, 1000),
-                                                          kProgrammaticScroll);
+  iframe_document->View()->LayoutViewport()->SetScrollOffset(
+      ScrollOffset(0, 1000), kProgrammaticScroll);
   Compositor().BeginFrame();
   test::RunPendingTasks();
   EXPECT_EQ(observer_delegate->CallCount(), 2);
@@ -530,7 +536,7 @@ TEST_F(IntersectionObserverTest, TrackedRootBookkeeping) {
   Persistent<Element> target = GetDocument().getElementById("target1");
   Persistent<IntersectionObserverInit> observer_init =
       IntersectionObserverInit::Create();
-  observer_init->setRoot(root);
+  observer_init->setRoot(ElementOrDocument::FromElement(root));
   Persistent<TestIntersectionObserverDelegate> observer_delegate =
       MakeGarbageCollected<TestIntersectionObserverDelegate>(GetDocument());
   Persistent<IntersectionObserver> observer =
@@ -679,7 +685,7 @@ TEST_F(IntersectionObserverTest, CachedRectsTest) {
   Element* target2 = GetDocument().getElementById("target2");
 
   IntersectionObserverInit* observer_init = IntersectionObserverInit::Create();
-  observer_init->setRoot(root);
+  observer_init->setRoot(ElementOrDocument::FromElement(root));
   DummyExceptionStateForTesting exception_state;
   TestIntersectionObserverDelegate* observer_delegate =
       MakeGarbageCollected<TestIntersectionObserverDelegate>(GetDocument());

third_party/blink/web_tests/external/wpt/intersection-observer/document-scrolling-element-root.html

@@ -28,18 +28,16 @@ iframe.onload = function() {
   runTestCycle(function() {
     assert_true(!!iframe, "iframe exists");
 
-    root = iframe.contentDocument.scrollingElement;
-    assert_true(!!root, "Root element exists.");
     target = iframe.contentDocument.getElementById("target");
     assert_true(!!target, "Target element exists.");
     var observer = new IntersectionObserver(function(changes) {
       entries = entries.concat(changes)
-    }, { root: root });
+    }, { root: iframe.contentDocument });
     observer.observe(target);
     entries = entries.concat(observer.takeRecords());
     assert_equals(entries.length, 0, "No initial notifications.");
     runTestCycle(step0, "First rAF.");
-  }, "Observer with explicit root which is the document's scrolling element.");
+  }, "Observer with explicit root which is the document.");
 };
 
 function step0() {