Add a UseCounter for clip CSS or -webkit-clip-path that clips positioned descendants.

Source/core/paint/DeprecatedPaintLayerPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/DeprecatedPaintLayerPainter.h"
 
 #include "core/frame/Settings.h"
 #include "core/layout/ClipPathOperation.h"
 #include "core/layout/LayoutBlock.h"
@@ skipping 102 matching lines @@
         ScopeRecorder scopeRecorder(*context);
         m_paintLayer.reflectionInfo()->paint(context, paintingInfo, localPaintFlags | PaintLayerPaintingReflection);
     }
 
     localPaintFlags |= PaintLayerPaintingCompositingAllPhases;
     paintLayerContents(context, paintingInfo, localPaintFlags, fragmentPolicy);
 }
 
 class ClipPathHelper {
 public:
-    ClipPathHelper(GraphicsContext* context, const DeprecatedPaintLayer& paintLayer, const DeprecatedPaintLayerPaintingInfo& paintingInfo, LayoutRect& rootRelativeBounds, bool& rootRelativeBoundsComputed,
+    ClipPathHelper(GraphicsContext* context, const DeprecatedPaintLayer& paintLayer, DeprecatedPaintLayerPaintingInfo& paintingInfo, LayoutRect& rootRelativeBounds, bool& rootRelativeBoundsComputed,
         const LayoutPoint& offsetFromRoot, PaintLayerFlags paintFlags)
         : m_resourceClipper(0), m_paintLayer(paintLayer), m_context(context)
     {
         const ComputedStyle& style = paintLayer.layoutObject()->styleRef();
 
         // Clip-path, like border radius, must not be applied to the contents of a composited-scrolling container.
         // It must, however, still be applied to the mask layer, so that the compositor can properly mask the
         // scrolling contents and scrollbars.
         if (!paintLayer.layoutObject()->hasClipPath() || (paintLayer.needsCompositedScrolling() && !(paintFlags & PaintLayerPaintingChildClippingMaskPhase)))
             return;
 
         m_clipperState = SVGClipPainter::ClipperNotApplied;
 
+        paintingInfo.ancestorHasClipPathClipping = true;
+
         ASSERT(style.clipPath());
         if (style.clipPath()->type() == ClipPathOperation::SHAPE) {
             ShapeClipPathOperation* clipPath = toShapeClipPathOperation(style.clipPath());
             if (clipPath->isValid()) {
                 if (!rootRelativeBoundsComputed) {
                     rootRelativeBounds = paintLayer.physicalBoundingBoxIncludingReflectionAndStackingChildren(offsetFromRoot);
                     rootRelativeBoundsComputed = true;
                 }
                 m_clipPathRecorder.emplace(*context, *paintLayer.layoutObject(), clipPath->path(FloatRect(rootRelativeBounds)));
             }
@@ skipping 24 matching lines @@
             SVGClipPainter(*m_resourceClipper).finishEffect(*m_paintLayer.layoutObject(), m_context, m_clipperState);
     }
 private:
     LayoutSVGResourceClipper* m_resourceClipper;
     Optional<ClipPathRecorder> m_clipPathRecorder;
     SVGClipPainter::ClipperState m_clipperState;
     const DeprecatedPaintLayer& m_paintLayer;
     GraphicsContext* m_context;
 };
 
-void DeprecatedPaintLayerPainter::paintLayerContents(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
+void DeprecatedPaintLayerPainter::paintLayerContents(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfoArg, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
 {
     ASSERT(m_paintLayer.isSelfPaintingLayer() || m_paintLayer.hasSelfPaintingLayerDescendant());
     ASSERT(!(paintFlags & PaintLayerAppliedTransform));
 
     bool isSelfPaintingLayer = m_paintLayer.isSelfPaintingLayer();
     bool isPaintingOverlayScrollbars = paintFlags & PaintLayerPaintingOverlayScrollbars;
     bool isPaintingScrollingContent = paintFlags & PaintLayerPaintingCompositingScrollingPhase;
     bool isPaintingCompositedForeground = paintFlags & PaintLayerPaintingCompositingForegroundPhase;
     bool isPaintingCompositedBackground = paintFlags & PaintLayerPaintingCompositingBackgroundPhase;
     bool isPaintingOverflowContents = paintFlags & PaintLayerPaintingOverflowContents;
     // Outline always needs to be painted even if we have no visible content. Also,
     // the outline is painted in the background phase during composited scrolling.
     // If it were painted in the foreground phase, it would move with the scrolled
     // content. When not composited scrolling, the outline is painted in the
     // foreground phase. Since scrolled contents are moved by paint invalidation in this
     // case, the outline won't get 'dragged along'.
     bool shouldPaintOutline = isSelfPaintingLayer && !isPaintingOverlayScrollbars
         && ((isPaintingScrollingContent && isPaintingCompositedBackground)
         || (!isPaintingScrollingContent && isPaintingCompositedForeground));
     bool shouldPaintContent = m_paintLayer.hasVisibleContent() && isSelfPaintingLayer && !isPaintingOverlayScrollbars;
 
     if (paintFlags & PaintLayerPaintingRootBackgroundOnly && !m_paintLayer.layoutObject()->isLayoutView() && !m_paintLayer.layoutObject()->isDocumentElement())
         return;
 
+    DeprecatedPaintLayerPaintingInfo paintingInfo = paintingInfoArg;
+
     // Ensure our lists are up-to-date.
     m_paintLayer.stackingNode()->updateLayerListsIfNeeded();
 
     LayoutPoint offsetFromRoot;
     m_paintLayer.convertToLayerCoords(paintingInfo.rootLayer, offsetFromRoot);
 
     if (m_paintLayer.compositingState() == PaintsIntoOwnBacking)
         offsetFromRoot.move(m_paintLayer.subpixelAccumulation());
     else
         offsetFromRoot.move(paintingInfo.subPixelAccumulation);
 
     LayoutRect rootRelativeBounds;
     bool rootRelativeBoundsComputed = false;
 
+    if (paintingInfo.ancestorHasClipPathClipping && m_paintLayer.layoutObject()->style()->position() != StaticPosition)
+        UseCounter::count(m_paintLayer.layoutObject()->document(), UseCounter::ClipPathOfPositionedElement);
+
     // These helpers output clip and compositing operations using a RAII pattern. Stack-allocated-varibles are destructed in the reverse order of construction,
     // so they are nested properly.
     ClipPathHelper clipPathHelper(context, m_paintLayer, paintingInfo, rootRelativeBounds, rootRelativeBoundsComputed, offsetFromRoot, paintFlags);
 
     Optional<CompositingRecorder> compositingRecorder;
     // Blending operations must be performed only with the nearest ancestor stacking context.
     // Note that there is no need to composite if we're painting the root.
     // FIXME: this should be unified further into DeprecatedPaintLayer::paintsWithTransparency().
     bool shouldCompositeForBlendMode = (!m_paintLayer.layoutObject()->isDocumentElement() || m_paintLayer.layoutObject()->isSVGRoot()) && m_paintLayer.stackingNode()->isStackingContext() && m_paintLayer.hasNonIsolatedDescendantWithBlendMode();
     if (shouldCompositeForBlendMode || m_paintLayer.paintsWithTransparency(paintingInfo.globalPaintFlags())) {
@@ skipping 147 matching lines @@
         Optional<ScopeRecorder> scopeRecorder;
         if (needsScope)
             scopeRecorder.emplace(*context);
         Optional<LayerClipRecorder> clipRecorder;
         if (parentLayer) {
             ClipRect clipRectForFragment(ancestorBackgroundClipRect);
             clipRectForFragment.moveBy(fragment.paginationOffset);
             clipRectForFragment.intersect(fragment.backgroundRect);
             if (clipRectForFragment.isEmpty())
                 continue;
-            if (needsToClip(paintingInfo, clipRectForFragment))
+            if (needsToClip(paintingInfo, clipRectForFragment)) {
+                if (m_paintLayer.layoutObject()->style()->position() != StaticPosition && clipRectForFragment.isClippedByClipCss())
+                    UseCounter::count(m_paintLayer.layoutObject()->document(), UseCounter::ClipCssOfPositionedElement);
                 clipRecorder.emplace(*context, *parentLayer->layoutObject(), DisplayItem::ClipLayerParent, clipRectForFragment, &paintingInfo, fragment.paginationOffset, paintFlags);
+            }
         }
 
         paintFragmentByApplyingTransform(context, paintingInfo, paintFlags, fragment.paginationOffset);
     }
 }
 
 void DeprecatedPaintLayerPainter::paintFragmentByApplyingTransform(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, const LayoutPoint& fragmentTranslation)
 {
     // This involves subtracting out the position of the layer in our current coordinate space, but preserving
     // the accumulated error for sub-pixel layout.
     LayoutPoint delta;
     m_paintLayer.convertToLayerCoords(paintingInfo.rootLayer, delta);
     delta.moveBy(fragmentTranslation);
     TransformationMatrix transform(m_paintLayer.renderableTransform(paintingInfo.globalPaintFlags()));
     IntPoint roundedDelta = roundedIntPoint(delta);
     transform.translateRight(roundedDelta.x(), roundedDelta.y());
     LayoutSize adjustedSubPixelAccumulation = paintingInfo.subPixelAccumulation + (delta - roundedDelta);
 
     Transform3DRecorder transform3DRecorder(*context, *m_paintLayer.layoutObject(), DisplayItem::Transform3DElementTransform, transform);
 
     // Now do a paint with the root layer shifted to be us.
     DeprecatedPaintLayerPaintingInfo transformedPaintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(transform.inverse().mapRect(paintingInfo.paintDirtyRect))), paintingInfo.globalPaintFlags(),
         adjustedSubPixelAccumulation, paintingInfo.paintingRoot);
+    transformedPaintingInfo.ancestorHasClipPathClipping = paintingInfo.ancestorHasClipPathClipping;
     paintLayerContentsAndReflection(context, transformedPaintingInfo, paintFlags, ForceSingleFragment);
 }
 
 void DeprecatedPaintLayerPainter::paintChildren(unsigned childrenToVisit, GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
 {
     if (!m_paintLayer.hasSelfPaintingLayerDescendant())
         return;
 
 #if ENABLE(ASSERT)
     LayerListMutationDetector mutationChecker(m_paintLayer.stackingNode());
@@ skipping 188 matching lines @@
     if (!m_paintLayer.containsDirtyOverlayScrollbars())
         return;
 
     DeprecatedPaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), paintFlags, LayoutSize(), paintingRoot);
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink