CSS Motion Path: Place offset-anchor on the path

third_party/WebKit/Source/core/style/ComputedStyle.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights
  * reserved.
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 1328 matching lines @@
       translate()->apply(result, boxSize);
 
     if (rotate())
       rotate()->apply(result, boxSize);
 
     if (scale())
       scale()->apply(result, boxSize);
   }
 
   if (applyMotionPath == IncludeMotionPath)
-    applyMotionPathTransform(originX, originY, result);
+    applyMotionPathTransform(originX, originY, boundingBox, result);
 
   for (const auto& operation : transform().operations())
     operation->apply(result, boxSize);
 
   if (applyTransformOrigin) {
     result.translate3d(-originX, -originY, -originZ);
   }
 }
 
 void ComputedStyle::applyMotionPathTransform(
     float originX,
     float originY,
+    const FloatRect& boundingBox,
     TransformationMatrix& transform) const {
   const StyleMotionData& motionData =
       m_rareNonInheritedData->m_transform->m_motion;
-  // TODO(ericwilligers): crbug.com/638055 Apply offset-position and
-  // offset-anchor.
+  // TODO(ericwilligers): crbug.com/638055 Apply offset-position.
   if (!motionData.m_path) {
     return;
   }
   const StylePath& motionPath = *motionData.m_path;
   float pathLength = motionPath.length();
   float distance = floatValueForLength(motionData.m_distance, pathLength);
   float computedDistance;
   if (motionPath.isClosed() && pathLength > 0) {
     computedDistance = fmod(distance, pathLength);
     if (computedDistance < 0)
       computedDistance += pathLength;
   } else {
     computedDistance = clampTo<float>(distance, 0, pathLength);
   }
 
   FloatPoint point;
   float angle;
   motionPath.path().pointAndNormalAtLength(computedDistance, point, angle);
 
   if (motionData.m_rotation.type == OffsetRotationFixed)
     angle = 0;
 
-  transform.translate(point.x() - originX, point.y() - originY);
+  float originShiftX = 0;
+  float originShiftY = 0;
+  if (RuntimeEnabledFeatures::cssOffsetPositionAnchorEnabled()) {
+    // TODO(ericwilligers): crbug.com/638055 Support offset-anchor: auto.
+    const LengthPoint& anchor = offsetAnchor();
+    originShiftX = floatValueForLength(anchor.x(), boundingBox.width()) -
+                   floatValueForLength(transformOriginX(), boundingBox.width());
+    originShiftY =
+        floatValueForLength(anchor.y(), boundingBox.height()) -
+        floatValueForLength(transformOriginY(), boundingBox.height());
+  }
+
+  transform.translate(point.x() - originX + originShiftX,
+                      point.y() - originY + originShiftY);
   transform.rotate(angle + motionData.m_rotation.angle);
+
+  if (RuntimeEnabledFeatures::cssOffsetPositionAnchorEnabled()) {
+    transform.translate(-originShiftX, -originShiftY);
+  }
 }
 
 void ComputedStyle::setTextShadow(PassRefPtr<ShadowList> s) {
   m_rareInheritedData.access()->textShadow = s;
 }
 
 void ComputedStyle::setBoxShadow(PassRefPtr<ShadowList> s) {
   m_rareNonInheritedData.access()->m_boxShadow = s;
 }
 
@@ skipping 998 matching lines @@
     if (value < 0)
       fvalue -= 0.5f;
     else
       fvalue += 0.5f;
   }
 
   return roundForImpreciseConversion<int>(fvalue / zoomFactor);
 }
 
 }  // namespace blink