Web Animations API: Deferred computation of interpolated values

Source/core/animation/LegacyStyleInterpolation.cpp

Index: Source/core/animation/LegacyStyleInterpolation.cpp
diff --git a/Source/core/animation/LegacyStyleInterpolation.cpp b/Source/core/animation/LegacyStyleInterpolation.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..0df30cb5a2965137d12d8716ef9f757b7333f329
--- /dev/null
+++ b/Source/core/animation/LegacyStyleInterpolation.cpp
@@ -0,0 +1,128 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "core/animation/LegacyStyleInterpolation.h"
+
+#include "core/css/CSSShadowValue.h"
+#include "core/css/Pair.h"
+#include "core/css/Rect.h"
+#include "core/css/resolver/AnimatedStyleBuilder.h"
+#include "core/css/resolver/StyleResolver.h"
+#include "core/css/resolver/StyleResolverState.h"
+
+namespace WebCore {
+
+PassRefPtrWillBeRawPtr<LegacyStyleInterpolation> LegacyStyleInterpolation::create(CSSValue& start, CSSValue& end, CSSPropertyID id, Element& element)
+{
+    if (interpolationRequiresStyleResolve(start) || interpolationRequiresStyleResolve(end))
+        return adoptRefWillBeNoop(new LegacyStyleInterpolation(&start, &end, id));
+    return create(
+        InterpolableAnimatableValue::create(StyleResolver::applyAndSnapshotAnimatableValue(element, id, start)),
+        InterpolableAnimatableValue::create(StyleResolver::applyAndSnapshotAnimatableValue(element, id, end)),
+        id);
+}
+
+void LegacyStyleInterpolation::apply(StyleResolverState& state) const
+{
+    if (!m_interpolationRequiresStyleResolve)
+        return AnimatedStyleBuilder::applyProperty(m_id, state, toInterpolableAnimatableValue(m_cachedValue.get())->value());
+
+    OwnPtrWillBeRawPtr<InterpolableValue> start = InterpolableAnimatableValue::create(StyleResolver::applyAndSnapshotAnimatableValue(*state.element(), m_id, *m_startCSSValue, state.style()));
+    OwnPtrWillBeRawPtr<InterpolableValue> end = InterpolableAnimatableValue::create(StyleResolver::applyAndSnapshotAnimatableValue(*state.element(), m_id, *m_endCSSValue, state.style()));
+    OwnPtrWillBeRawPtr<InterpolableValue> interpolated = start->interpolate(*end, m_cachedFraction);
+    AnimatedStyleBuilder::applyProperty(m_id, state, toInterpolableAnimatableValue(interpolated.get())->value());
+}
+
+bool LegacyStyleInterpolation::interpolationRequiresStyleResolve(const CSSValue& value)
+{
+    if (value.isPrimitiveValue())
+        return interpolationRequiresStyleResolve(toCSSPrimitiveValue(value));
+
+    if (value.isInheritedValue())
+        return true;
+
+    if (value.isValueList()) {
+        const CSSValueList& valueList = toCSSValueList(value);
+        size_t length = valueList.length();
+        for (size_t index = 0; index < length; ++index) {
+            if (interpolationRequiresStyleResolve(*valueList.item(index)))
+                return true;
+        }
+        return false;
+    }
+
+    if (value.isShadowValue()) {
+        const CSSShadowValue& shadowValue = toCSSShadowValue(value);
+        return (shadowValue.x && interpolationRequiresStyleResolve(*shadowValue.x))
+            || (shadowValue.y && interpolationRequiresStyleResolve(*shadowValue.y))
+            || (shadowValue.blur && interpolationRequiresStyleResolve(*shadowValue.blur))
+            || (shadowValue.spread && interpolationRequiresStyleResolve(*shadowValue.spread))
+            || (shadowValue.style && interpolationRequiresStyleResolve(*shadowValue.style))
+            || (shadowValue.color && interpolationRequiresStyleResolve(*shadowValue.color));
+    }
+
+    return false;

[dstockwell, 2014/05/09 05:57:09]

Which cases aren't handled here? Can this be a switch?

+}
+
+bool LegacyStyleInterpolation::interpolationRequiresStyleResolve(const CSSPrimitiveValue& primitiveValue)
+{
+    if (primitiveValue.isCalculated()) {
+        CSSLengthArray lengthArray;
+        CSSPrimitiveValue::zeroLengthArray(lengthArray);
+        primitiveValue.accumulateLengthArray(lengthArray);
+        return lengthArray[CSSPrimitiveValue::UnitTypeFontSize]

[dstockwell, 2014/05/09 05:57:09]

Clearer to use != 0 here.

+            || lengthArray[CSSPrimitiveValue::UnitTypeFontXSize]
+            || lengthArray[CSSPrimitiveValue::UnitTypeRootFontSize]
+            || lengthArray[CSSPrimitiveValue::UnitTypeZeroCharacterWidth]
+            || lengthArray[CSSPrimitiveValue::UnitTypeViewportWidth]
+            || lengthArray[CSSPrimitiveValue::UnitTypeViewportHeight]
+            || lengthArray[CSSPrimitiveValue::UnitTypeViewportMin]
+            || lengthArray[CSSPrimitiveValue::UnitTypeViewportMax];

[dstockwell, 2014/05/09 05:57:09]

Presumably this logic should live somewhere else? How does someone know to
update this when we add new units?

+    }
+
+    if (primitiveValue.isLength())
+        return primitiveValue.isFontRelativeLength() || primitiveValue.isViewportPercentageLength();
+
+    if (Pair* pair = primitiveValue.getPairValue()) {
+        return interpolationRequiresStyleResolve(*pair->first())
+            || interpolationRequiresStyleResolve(*pair->second());
+    }
+
+    if (Rect* rect = primitiveValue.getRectValue()) {
+        return interpolationRequiresStyleResolve(*rect->top())
+            || interpolationRequiresStyleResolve(*rect->right())
+            || interpolationRequiresStyleResolve(*rect->bottom())
+            || interpolationRequiresStyleResolve(*rect->left());
+    }
+
+    if (Quad* quad = primitiveValue.getQuadValue()) {
+        return interpolationRequiresStyleResolve(*quad->top())
+            || interpolationRequiresStyleResolve(*quad->right())
+            || interpolationRequiresStyleResolve(*quad->bottom())
+            || interpolationRequiresStyleResolve(*quad->left());
+    }
+
+    switch (primitiveValue.getValueID()) {
+    case CSSValueBolder:
+    case CSSValueCurrentcolor:
+    case CSSValueHigher:
+    case CSSValueLarger:
+    case CSSValueLighter:
+    case CSSValueLower:
+    case CSSValueSmaller:
+        return true;
+    default:

[dstockwell, 2014/05/09 05:57:09]

How do we avoid hitting other important cases?

+        return false;
+    }
+}
+
+void LegacyStyleInterpolation::trace(Visitor* visitor)
+{
+    StyleInterpolation::trace(visitor);
+    visitor->trace(m_startCSSValue);
+    visitor->trace(m_endCSSValue);
+}
+
+}