[WIP] CSS Motion Path: offset-anchor and offset-position

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

Index: third_party/WebKit/Source/core/style/ComputedStyle.cpp
diff --git a/third_party/WebKit/Source/core/style/ComputedStyle.cpp b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
index 8188e6012b3af91a0b81babb7c48af57ac993297..ac48e69a0ea36a37c2516af243da8b00b5d3bb62 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.cpp
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
@@ -988,6 +988,7 @@ static bool hasPropertyThatCreatesStackingContext(const Vector<CSSPropertyID>& p
         case CSSPropertyPosition:
         case CSSPropertyMixBlendMode:
         case CSSPropertyIsolation:
+        case CSSPropertyOffsetPath:
             return true;
         default:
             break;
@@ -1097,7 +1098,7 @@ void ComputedStyle::applyTransform(TransformationMatrix& result, const LayoutSiz
 
 void ComputedStyle::applyTransform(TransformationMatrix& result, const FloatRect& boundingBox, ApplyTransformOrigin applyOrigin, ApplyMotionPath applyMotionPath, ApplyIndependentTransformProperties applyIndependentTransformProperties) const
 {
-    if (!hasMotionPath())
+    if (!hasOffsetPath())
         applyMotionPath = ExcludeMotionPath;
     bool applyTransformOrigin = requireTransformOrigin(applyOrigin, applyMotionPath);
 
@@ -1127,7 +1128,7 @@ void ComputedStyle::applyTransform(TransformationMatrix& result, const FloatRect
     }
 
     if (applyMotionPath == ComputedStyle::IncludeMotionPath)
-        applyMotionPathTransform(originX, originY, result);
+        applyMotionPathTransform(originX, originY, boundingBox, result);
 
     const Vector<RefPtr<TransformOperation>>& transformOperations = transform().operations();
     unsigned size = transformOperations.size();
@@ -1139,13 +1140,13 @@ void ComputedStyle::applyTransform(TransformationMatrix& result, const FloatRect
     }
 }
 
-void ComputedStyle::applyMotionPathTransform(float originX, float originY, TransformationMatrix& transform) const
+void ComputedStyle::applyMotionPathTransform(float originX, float originY, const FloatRect& boundingBox, TransformationMatrix& transform) const
 {
     const StyleMotionData& motionData = m_rareNonInheritedData->m_transform->m_motion;
     ASSERT(motionData.m_path);
     const StylePath& motionPath = *motionData.m_path;
     float pathLength = motionPath.length();
-    float distance = floatValueForLength(motionData.m_offset, pathLength);
+    float distance = floatValueForLength(motionData.m_distance, pathLength);
     float computedDistance;
     if (motionPath.isClosed() && pathLength > 0) {
         computedDistance = fmod(distance, pathLength);
@@ -1159,10 +1160,27 @@ void ComputedStyle::applyMotionPathTransform(float originX, float originY, Trans
     float angle;
     motionPath.path().pointAndNormalAtLength(computedDistance, point, angle);
 
-    if (motionData.m_rotation.type == MotionRotationFixed)
+    if (motionData.m_rotation.type == OffsetRotationFixed)
         angle = 0;
 
-    transform.translate(point.x() - originX, point.y() - originY);
+    float translateX = point.x();
+    float translateY = point.y();
+    const LengthPoint& position = offsetPosition();
+    if (position.x() == Auto) {
+        translateX -= originX;
+        translateY -= originY;
+    } else {
+        translateX += floatValueForLength(position.x(), boundingBox.width()) - floatValueForLength(left(), boundingBox.width());
+        translateY += floatValueForLength(position.y(), boundingBox.height()) - floatValueForLength(top(), boundingBox.height());
+    }
+
+    const LengthPoint& anchor = offsetAnchor();
+    // TODO(ericwilligers): Consider interaction between position, anchor, rotation
+    if (anchor.x() != Auto) {
+        translateX += floatValueForLength(left(), boundingBox.width()) - boundingBox.x() - floatValueForLength(anchor.x(), boundingBox.width());
+        translateY += floatValueForLength(top(), boundingBox.height()) - boundingBox.y() - floatValueForLength(anchor.y(), boundingBox.height());
+    }
+    transform.translate(translateX, translateY);
     transform.rotate(angle + motionData.m_rotation.angle);
 }
 
@@ -1843,7 +1861,7 @@ void ComputedStyle::setMarginEnd(const Length& margin)
     }
 }
 
-void ComputedStyle::setMotionPath(PassRefPtr<StylePath> path)
+void ComputedStyle::setOffsetPath(PassRefPtr<StylePath> path)
 {
     m_rareNonInheritedData.access()->m_transform.access()->m_motion.m_path = path;
 }