CSS Motion Path: offset-anchor should default to auto

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 1350 matching lines @@
     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.
   if (!motionData.m_path) {
     return;
   }
+  const LengthPoint& position = offsetPosition();
+  const LengthPoint& anchor = offsetAnchor();
   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;
 
   float originShiftX = 0;
   float originShiftY = 0;
-  if (RuntimeEnabledFeatures::cssOffsetPositionAnchorEnabled()) {
-    // TODO(ericwilligers): crbug.com/638055 Support offset-anchor: auto.
-    const LengthPoint& anchor = offsetAnchor();
+  if (position.x() != Length(Auto) || anchor.x() != Length(Auto)) {

[sashab, 2016/12/12 01:11:26]

You removed a runtime enabled feature flag? Please add that to the CL
description.

Also is this if statement needed? I feel like the originShift code should apply
and work and handle the Auto case. Maybe I'm misunderstanding what this is for;
if so, a comment is needed.

[Eric Willigers, 2016/12/12 01:57:14]

comments added

     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()) {
+  if (position.x() != Length(Auto) || anchor.x() != Length(Auto))

[sashab, 2016/12/12 01:11:26]

Why only x() and not y()?

[Eric Willigers, 2016/12/12 01:57:14]

position and anchor are 
<position> | auto
i.e. either a pair of positions, or auto.

Checking y would be redundant.

     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 1027 matching lines @@
     if (value < 0)
       fvalue -= 0.5f;
     else
       fvalue += 0.5f;
   }
 
   return roundForImpreciseConversion<int>(fvalue / zoomFactor);
 }
 
 }  // namespace blink