Fix computation of animated transform w/ different from/to transform types

Source/core/svg/SVGTransformList.cpp

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2012. 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
@@ skipping 301 matching lines @@
     RefPtr<SVGTransformList> fromList = isToAnimation ? this : toSVGTransformList(fromValue);
     RefPtr<SVGTransformList> toList = toSVGTransformList(toValue);
     RefPtr<SVGTransformList> toAtEndOfDurationList = toSVGTransformList(toAtEndOfDurationValue);
 
     size_t toListSize = toList->length();
     if (!toListSize)
         return;
 
     // Get a reference to the from value before potentially cleaning it out (in the case of a To animation.)
     RefPtr<SVGTransform> toTransform = toList->at(0);
-    RefPtr<SVGTransform> effectiveFrom = fromList->length() ? fromList->at(0) : SVGTransform::create(toTransform->transformType(), SVGTransform::ConstructZeroTransform);
+    RefPtr<SVGTransform> effectiveFrom;
+    // If there's an existing 'from'/underlying value of the same type use that, else use a "zero transform".
+    if (fromList->length() && fromList->at(0)->transformType() == toTransform->transformType())
+        effectiveFrom = fromList->at(0);
+    else
+        effectiveFrom = SVGTransform::create(toTransform->transformType(), SVGTransform::ConstructZeroTransform);
 
     // Never resize the animatedTransformList to the toList size, instead either clear the list or append to it.
-    if (!isEmpty() && !animationElement->isAdditive())
+    if (!isEmpty() && (!animationElement->isAdditive() || isToAnimation))
         clear();
 
     RefPtr<SVGTransform> currentTransform = SVGTransformDistance(effectiveFrom, toTransform).scaledDistance(percentage).addToSVGTransform(effectiveFrom);
     if (animationElement->isAccumulated() && repeatCount) {
         RefPtr<SVGTransform> effectiveToAtEnd = !toAtEndOfDurationList->isEmpty() ? toAtEndOfDurationList->at(0) : SVGTransform::create(toTransform->transformType(), SVGTransform::ConstructZeroTransform);

[pdr., 2014/06/13 17:29:41]

Can you assert here that the transform types are the same?

[fs, 2014/06/16 08:13:49]

SVGTransformDistance::addSVGTransforms() asserts that, so that should be covered
already I think.

         append(SVGTransformDistance::addSVGTransforms(currentTransform, effectiveToAtEnd, repeatCount));
     } else {
         append(currentTransform);
     }
 }
 
 float SVGTransformList::calculateDistance(PassRefPtr<SVGPropertyBase> toValue, SVGElement*)
 {
     // FIXME: This is not correct in all cases. The spec demands that each component (translate x and y for example)
     // is paced separately. To implement this we need to treat each component as individual animation everywhere.
 
     RefPtr<SVGTransformList> toList = toSVGTransformList(toValue);
     if (isEmpty() || length() != toList->length())
         return -1;
 
     ASSERT(length() == 1);
     if (at(0)->transformType() == toList->at(0)->transformType())
         return -1;
 
     // Spec: http://www.w3.org/TR/SVG/animate.html#complexDistances
     // Paced animations assume a notion of distance between the various animation values defined by the ‘to’, ‘from’, ‘by’ and ‘values’ attributes.
     // Distance is defined only for scalar types (such as <length>), colors and the subset of transformation types that are supported by ‘animateTransform’.
     return SVGTransformDistance(at(0), toList->at(0)).distance();
 }
 
 }