Bug 1556556 - Add a "relative to layout viewport" option for display list building. r=mstange,mattwoodrow

Use it in document.elementFromPoint().

Differential Revision: https://phabricator.services.mozilla.com/D68914

dom/base/DocumentOrShadowRoot.cpp

@@ -457,33 +457,41 @@ static void QueryNodesFromPoint(DocumentOrShadowRoot& aRoot, float aX, float aY,
 }  // namespace
 
 Element* DocumentOrShadowRoot::ElementFromPoint(float aX, float aY) {
-  return ElementFromPointHelper(aX, aY, false, true);
+  return ElementFromPointHelper(aX, aY, false, true, true);
 }
 
 void DocumentOrShadowRoot::ElementsFromPoint(
     float aX, float aY, nsTArray<RefPtr<Element>>& aElements) {
-  QueryNodesFromPoint(*this, aX, aY, {}, FlushLayout::Yes, Multiple::Yes,
-                      aElements);
+  QueryNodesFromPoint(*this, aX, aY,
+                      FrameForPointOption::IsRelativeToLayoutViewport,
+                      FlushLayout::Yes, Multiple::Yes, aElements);
 }
 
 void DocumentOrShadowRoot::NodesFromPoint(float aX, float aY,
                                           nsTArray<RefPtr<nsINode>>& aNodes) {
-  QueryNodesFromPoint(*this, aX, aY, {}, FlushLayout::Yes, Multiple::Yes,
-                      aNodes);
+  QueryNodesFromPoint(*this, aX, aY,
+                      FrameForPointOption::IsRelativeToLayoutViewport,
+                      FlushLayout::Yes, Multiple::Yes, aNodes);
 }
 
 nsINode* DocumentOrShadowRoot::NodeFromPoint(float aX, float aY) {
   AutoTArray<RefPtr<nsINode>, 1> nodes;
-  QueryNodesFromPoint(*this, aX, aY, {}, FlushLayout::Yes, Multiple::No, nodes);
+  QueryNodesFromPoint(*this, aX, aY,
+                      FrameForPointOption::IsRelativeToLayoutViewport,
+                      FlushLayout::Yes, Multiple::No, nodes);
   return nodes.SafeElementAt(0);
 }
 
 Element* DocumentOrShadowRoot::ElementFromPointHelper(
-    float aX, float aY, bool aIgnoreRootScrollFrame, bool aFlushLayout) {
+    float aX, float aY, bool aIgnoreRootScrollFrame, bool aFlushLayout,
+    bool aIsRelativeToLayoutViewport) {
   EnumSet<FrameForPointOption> options;
   if (aIgnoreRootScrollFrame) {
     options += FrameForPointOption::IgnoreRootScrollFrame;
   }
+  if (aIsRelativeToLayoutViewport) {
+    options += FrameForPointOption::IsRelativeToLayoutViewport;
+  }
 
   auto flush = aFlushLayout ? FlushLayout::Yes : FlushLayout::No;
 

dom/base/DocumentOrShadowRoot.h

@@ -135,7 +135,8 @@ class DocumentOrShadowRoot {
    */
   Element* ElementFromPointHelper(float aX, float aY,
                                   bool aIgnoreRootScrollFrame,
-                                  bool aFlushLayout);
+                                  bool aFlushLayout,
+                                  bool aIsRelativeToLayoutViewport);
 
   void NodesFromRect(float aX, float aY, float aTopSize, float aRightSize,
                      float aBottomSize, float aLeftSize,

dom/base/nsDOMWindowUtils.cpp

@@ -1155,8 +1155,8 @@ nsDOMWindowUtils::ElementFromPoint(float aX, float aY,
   nsCOMPtr<Document> doc = GetDocument();
   NS_ENSURE_STATE(doc);
 
-  RefPtr<Element> el =
-      doc->ElementFromPointHelper(aX, aY, aIgnoreRootScrollFrame, aFlushLayout);
+  RefPtr<Element> el = doc->ElementFromPointHelper(
+      aX, aY, aIgnoreRootScrollFrame, aFlushLayout, false);
   el.forget(aReturn);
   return NS_OK;
 }

dom/events/ContentEventHandler.cpp

@@ -2648,7 +2648,7 @@ nsresult ContentEventHandler::OnQueryDOMWidgetHittest(
           docFrameRect.y);
 
   Element* contentUnderMouse = mDocument->ElementFromPointHelper(
-      eventLocCSS.x, eventLocCSS.y, false, false);
+      eventLocCSS.x, eventLocCSS.y, false, false, false);
   if (contentUnderMouse) {
     nsIWidget* targetWidget = nullptr;
     nsIFrame* targetFrame = contentUnderMouse->GetPrimaryFrame();

layout/base/nsLayoutUtils.cpp

@@ -3187,6 +3187,9 @@ nsresult nsLayoutUtils::GetFramesForArea(
       builder.SetIgnoreScrollFrame(rootScrollFrame);
     }
   }
+  if (aOptions.contains(FrameForPointOption::IsRelativeToLayoutViewport)) {
+    builder.SetIsRelativeToLayoutViewport();
+  }
   if (aOptions.contains(FrameForPointOption::IgnoreCrossDoc)) {
     builder.SetDescendIntoSubdocuments(false);
   }

layout/base/nsLayoutUtils.h

@@ -878,6 +878,12 @@ class nsLayoutUtils {
      * When set, return only content that is actually visible.
      */
     OnlyVisible,
+    /**
+     * When set, coordinates are interpreted as being relative to the layout
+     * viewport. When not set, coordinates are interpreted as being relative
+     * to the visual viewport.
+     */
+    IsRelativeToLayoutViewport,
   };
 
   /**

layout/painting/nsDisplayList.cpp

@@ -1228,6 +1228,7 @@ nsDisplayListBuilder::nsDisplayListBuilder(nsIFrame* aReferenceFrame,
       mIsInActiveDocShell(false),
       mBuildAsyncZoomContainer(false),
       mContainsBackdropFilter(false),
+      mIsRelativeToLayoutViewport(false),
       mHitTestArea(),
       mHitTestInfo(CompositorHitTestInvisibleToHit) {
   MOZ_COUNT_CTOR(nsDisplayListBuilder);
@@ -1450,9 +1451,15 @@ AnimatedGeometryRoot* nsDisplayListBuilder::FindAnimatedGeometryRootFor(
   return FindAnimatedGeometryRootFor(aItem->Frame());
 }
 
+void nsDisplayListBuilder::SetIsRelativeToLayoutViewport() {
+  mIsRelativeToLayoutViewport = true;
+  UpdateShouldBuildAsyncZoomContainer();
+}
+
 void nsDisplayListBuilder::UpdateShouldBuildAsyncZoomContainer() {
   Document* document = mReferenceFrame->PresContext()->Document();
-  mBuildAsyncZoomContainer = nsLayoutUtils::AllowZoomingForDocument(document);
+  mBuildAsyncZoomContainer = !mIsRelativeToLayoutViewport &&
+                             nsLayoutUtils::AllowZoomingForDocument(document);
 }
 
 // Certain prefs may cause display list items to be added or removed when they

layout/painting/nsDisplayList.h

@@ -585,6 +585,10 @@ class nsDisplayListBuilder {
    * Get the scrollframe to ignore, if any.
    */
   nsIFrame* GetIgnoreScrollFrame() { return mIgnoreScrollFrame; }
+  void SetIsRelativeToLayoutViewport();
+  bool IsRelativeToLayoutViewport() const {
+    return mIsRelativeToLayoutViewport;
+  }
   /**
    * Get the ViewID of the nearest scrolling ancestor frame.
    */
@@ -2030,6 +2034,7 @@ class nsDisplayListBuilder {
   bool mIsInActiveDocShell;
   bool mBuildAsyncZoomContainer;
   bool mContainsBackdropFilter;
+  bool mIsRelativeToLayoutViewport;
 
   nsRect mHitTestArea;
   CompositorHitTestInfo mHitTestInfo;