Add support for <basic-shape> to 'clip-path' on SVG elements

third_party/WebKit/Source/core/paint/ClipPathClipper.cpp

 // Copyright 2016 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 "core/paint/ClipPathClipper.h"
 
 #include "core/layout/svg/LayoutSVGResourceClipper.h"
+#include "core/layout/svg/SVGResources.h"
+#include "core/layout/svg/SVGResourcesCache.h"
+#include "core/paint/SVGClipPainter.h"
 #include "core/style/ClipPathOperation.h"
 #include "platform/graphics/paint/ClipPathRecorder.h"
 
 namespace blink {
 
+namespace {
+
+LayoutSVGResourceClipper* resolveElementReference(
+    const LayoutObject& layoutObject,
+    const ReferenceClipPathOperation& referenceClipPathOperation)
+{
+    if (layoutObject.isSVG()) {
+        // The reference will have been resolved in
+        // SVGResources::buildResources, so we can just use the LayoutObject's
+        // SVGResources.
+        SVGResources* resources = SVGResourcesCache::cachedResourcesForLayoutObject(&layoutObject);
+        return resources ? resources->clipper() : nullptr;
+    }
+    // TODO(fs): It doesn't work with forward or external SVG references (https://bugs.webkit.org/show_bug.cgi?id=90405)
+    Element* element = layoutObject.document().getElementById(referenceClipPathOperation.fragment());
+    if (!isSVGClipPathElement(element) || !element->layoutObject())
+        return nullptr;
+    return toLayoutSVGResourceClipper(toLayoutSVGResourceContainer(element->layoutObject()));
+}
+
+} // namespace
+
 ClipPathClipper::ClipPathClipper(
     GraphicsContext& context,
+    ClipPathOperation& clipPathOperation,
     const LayoutObject& layoutObject,
     const FloatRect& referenceBox,
     const FloatPoint& origin)
     : m_resourceClipper(nullptr)
-    , m_clipperState(SVGClipPainter::ClipperNotApplied)
+    , m_clipperState(ClipperState::NotApplied)
     , m_layoutObject(layoutObject)
     , m_context(context)
 {
-    DCHECK(layoutObject.styleRef().clipPath());
-    ClipPathOperation* clipPathOperation = layoutObject.styleRef().clipPath();
-    if (clipPathOperation->type() == ClipPathOperation::SHAPE) {
-        ShapeClipPathOperation* shape = toShapeClipPathOperation(clipPathOperation);
-        if (!shape->isValid())
+    if (clipPathOperation.type() == ClipPathOperation::SHAPE) {
+        ShapeClipPathOperation& shape = toShapeClipPathOperation(clipPathOperation);
+        if (!shape.isValid())
             return;
-        m_clipPathRecorder.emplace(context, layoutObject, shape->path(referenceBox));
+        m_clipPathRecorder.emplace(context, layoutObject, shape.path(referenceBox));
+        m_clipperState = ClipperState::AppliedPath;
     } else {
-        DCHECK_EQ(clipPathOperation->type(), ClipPathOperation::REFERENCE);
-        ReferenceClipPathOperation* referenceClipPathOperation = toReferenceClipPathOperation(clipPathOperation);
-        // TODO(fs): It doesn't work with forward or external SVG references (https://bugs.webkit.org/show_bug.cgi?id=90405)
-        Element* element = layoutObject.document().getElementById(referenceClipPathOperation->fragment());
-        if (!isSVGClipPathElement(element) || !element->layoutObject())
+        DCHECK_EQ(clipPathOperation.type(), ClipPathOperation::REFERENCE);
+        LayoutSVGResourceClipper* clipper = resolveElementReference(
+            layoutObject, toReferenceClipPathOperation(clipPathOperation));
+        if (!clipper)
             return;
-        LayoutSVGResourceClipper* clipper = toLayoutSVGResourceClipper(toLayoutSVGResourceContainer(element->layoutObject()));
         // Compute the (conservative) bounds of the clip-path.
         FloatRect clipPathBounds = clipper->resourceBoundingBox(referenceBox);
         // When SVG applies the clip, and the coordinate system is "userspace on use", we must explicitly pass in
         // the offset to have the clip paint in the correct location. When the coordinate system is
         // "object bounding box" the offset should already be accounted for in the reference box.
         FloatPoint originTranslation;
         if (clipper->clipPathUnits() == SVGUnitTypes::kSvgUnitTypeUserspaceonuse) {
             clipPathBounds.moveBy(origin);
             originTranslation = origin;
         }
         if (!SVGClipPainter(*clipper).prepareEffect(layoutObject, referenceBox,
             clipPathBounds, originTranslation, context, m_clipperState))
             return;
         m_resourceClipper = clipper;
     }
 }
 
 ClipPathClipper::~ClipPathClipper()
 {
     if (m_resourceClipper)
         SVGClipPainter(*m_resourceClipper).finishEffect(m_layoutObject, m_context, m_clipperState);
 }
 
 } // namespace blink