Web Animations CSS: Support animation of background-position and background-image

Source/core/animation/css/CSSAnimatableValueFactory.cpp

Index: Source/core/animation/css/CSSAnimatableValueFactory.cpp
diff --git a/Source/core/animation/css/CSSAnimatableValueFactory.cpp b/Source/core/animation/css/CSSAnimatableValueFactory.cpp
index 8242cb306ebccbef500b7e92a6683c47da8985f7..7d9a1f49ad0e3aac79922fb6a96324e8c15fa570 100644
--- a/Source/core/animation/css/CSSAnimatableValueFactory.cpp
+++ b/Source/core/animation/css/CSSAnimatableValueFactory.cpp
@@ -39,6 +39,7 @@
 #include "core/animation/AnimatableLength.h"
 #include "core/animation/AnimatableLengthBox.h"
 #include "core/animation/AnimatableLengthSize.h"
+#include "core/animation/AnimatableRepeatable.h"
 #include "core/animation/AnimatableSVGLength.h"
 #include "core/animation/AnimatableSVGPaint.h"
 #include "core/animation/AnimatableShapeValue.h"
@@ -113,6 +114,32 @@ inline static PassRefPtr<AnimatableValue> createFromLengthSize(const LengthSize
         createFromLength(lengthSize.height(), style));
 }
 
+template<typename T>
+static inline PassRefPtr<AnimatableValue> createFrom(T, const RenderStyle*);
+
+template <>
+PassRefPtr<AnimatableValue> createFrom<Length>(Length length, const RenderStyle* style)
+{
+    return createFromLength(length, style);
+}
+
+template <>
+PassRefPtr<AnimatableValue> createFrom<StyleImage*>(StyleImage* image, const RenderStyle*)
+{
+    return AnimatableImage::create(image);
+}
+
+template<typename T>
+inline static PassRefPtr<AnimatableValue> createFromFillLayers(const FillLayer* fillLayer, T getter, bool (FillLayer::*isSet)() const, const RenderStyle* style)

[dstockwell, 2013/10/08 23:02:46]

This seems a bit yuck. Couldn't this just be a single method templated on
CSSPropertyID? No need for function pointers...

[alancutter (OOO until 2018), 2013/10/09 07:20:55]

I agree that function pointers and code duplication aren't very pretty but IMO
the templated switch solution is even uglier. I'd added it to the patch for you
to see. Perhaps I'm doing it in an ugly way but it's not entirely clear to me
how to make it succinct without function pointers.

+{
+    Vector<RefPtr<AnimatableValue> > values;
+    while (fillLayer && (fillLayer->*isSet)()) {
+        values.append(createFrom((fillLayer->*getter)(), style));
+        fillLayer = fillLayer->next();
+    }
+    return AnimatableRepeatable::create(values);
+}
+
 PassRefPtr<AnimatableValue> CSSAnimatableValueFactory::createFromColor(CSSPropertyID property, const RenderStyle* style)
 {
     Color color = style->colorIncludingFallback(property, false);
@@ -138,6 +165,12 @@ PassRefPtr<AnimatableValue> CSSAnimatableValueFactory::create(CSSPropertyID prop
     switch (property) {
     case CSSPropertyBackgroundColor:
         return createFromColor(property, style);
+    case CSSPropertyBackgroundImage:
+        return createFromFillLayers(style->backgroundLayers(), &FillLayer::image, &FillLayer::isImageSet, style);
+    case CSSPropertyBackgroundPositionX:
+        return createFromFillLayers(style->backgroundLayers(), &FillLayer::xPosition, &FillLayer::isXPositionSet, style);
+    case CSSPropertyBackgroundPositionY:
+        return createFromFillLayers(style->backgroundLayers(), &FillLayer::yPosition, &FillLayer::isYPositionSet, style);
     case CSSPropertyBaselineShift:
         return AnimatableSVGLength::create(style->baselineShiftValue());
     case CSSPropertyBorderBottomColor: