Common up SVG transform "change detection" (classification)

third_party/WebKit/Source/core/layout/svg/LayoutSVGViewportContainer.cpp

 /*
  * Copyright (C) 2004, 2005, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Google, Inc.
  *
  * 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 52 matching lines @@
         setNeedsTransformUpdate();
     }
 }
 
 void LayoutSVGViewportContainer::setNeedsTransformUpdate()
 {
     setMayNeedPaintInvalidationSubtree();
     m_needsTransformUpdate = true;
 }
 
-static std::pair<double, double> scaleReference(const AffineTransform& transform)
-{
-    return std::make_pair(transform.xScaleSquared(), transform.yScaleSquared());
-}
-
-LayoutSVGContainer::TransformChange LayoutSVGViewportContainer::calculateLocalTransform()
+SVGTransformChange LayoutSVGViewportContainer::calculateLocalTransform()
 {
     if (!m_needsTransformUpdate)
-        return TransformChange::None;
+        return SVGTransformChange::None;
 
-    std::pair<double, double> oldScale = scaleReference(m_localToParentTransform);
+    SVGTransformChangeDetector changeDetector(m_localToParentTransform);
     m_localToParentTransform = AffineTransform::translation(m_viewport.x(), m_viewport.y()) * viewportTransform();
     m_needsTransformUpdate = false;
-    return scaleReference(m_localToParentTransform) != oldScale
-        ? TransformChange::Full : TransformChange::ScaleInvariant;
+    return changeDetector.computeChange(m_localToParentTransform);
 }
 
 AffineTransform LayoutSVGViewportContainer::viewportTransform() const
 {
     ASSERT(element());
     if (isSVGSVGElement(*element())) {
         SVGSVGElement* svg = toSVGSVGElement(element());
         return svg->viewBoxToViewTransform(m_viewport.width(), m_viewport.height());
     }
 
     return AffineTransform();
 }
 
 bool LayoutSVGViewportContainer::pointIsInsideViewportClip(const FloatPoint& pointInParent)
 {
     // Respect the viewport clip (which is in parent coords)
     if (!SVGLayoutSupport::isOverflowHidden(this))
         return true;
 
     return m_viewport.contains(pointInParent);
 }
 
 void LayoutSVGViewportContainer::paint(const PaintInfo& paintInfo, const LayoutPoint& paintOffset) const
 {
     SVGContainerPainter(*this).paint(paintInfo);
 }
 
 } // namespace blink