Web Animations API: Deferred computation of interpolated values

Source/core/animation/LegacyStyleInterpolation.cpp

+// 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/resolver/AnimatedStyleBuilder.h"
+#include "core/css/resolver/StyleResolverState.h"
+
+namespace WebCore {
+
+PassRefPtrWillBeRawPtr<LegacyStyleInterpolation> LegacyStyleInterpolation::create(PassRefPtrWillBeRawPtr<InterpolableValuePromise> start, PassRefPtrWillBeRawPtr<InterpolableValuePromise> end, CSSPropertyID id)
+{
+    RefPtrWillBeRawPtr<AnimatableValue> startValue = start->extractAnimatableValue();
+    RefPtrWillBeRawPtr<AnimatableValue> endValue = end->extractAnimatableValue();
+    if (startValue && endValue)
+        return create(startValue, endValue, id);
+    return adoptRefWillBeNoop(new LegacyStyleInterpolation(start, end, id));
+}
+
+void LegacyStyleInterpolation::apply(StyleResolverState& state) const
+{
+    if (m_cachedValue) {
+        AnimatedStyleBuilder::applyProperty(m_id, state, toInterpolableAnimatableValue(m_cachedValue.get())->value());
+    } else {
+        OwnPtrWillBeRawPtr<InterpolableValue> start = m_startPromise->extract(state, m_id);
+        OwnPtrWillBeRawPtr<InterpolableValue> end = m_endPromise->extract(state, m_id);
+        OwnPtrWillBeRawPtr<InterpolableValue> interpolated = start->interpolate(*end, m_cachedFraction);
+        AnimatedStyleBuilder::applyProperty(m_id, state, toInterpolableAnimatableValue(interpolated.get())->value());
+        // We avoid caching to remain responsive outside of our active interval.
+    }
+}
+
+void LegacyStyleInterpolation::trace(Visitor* visitor)
+{
+    StyleInterpolation::trace(visitor);
+    visitor->trace(m_startPromise);
+    visitor->trace(m_endPromise);
+}
+
+}