Basic ScrollTimeline implementation for Animation Worklet

third_party/WebKit/Source/core/animation/ScrollTimeline.h

+// Copyright 2017 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.
+
+#ifndef ScrollTimeline_h
+#define ScrollTimeline_h
+
+#include "core/CoreExport.h"
+#include "core/animation/AnimationTimeline.h"
+#include "core/animation/ScrollTimelineOptions.h"
+#include "core/dom/Element.h"
+#include "platform/bindings/ScriptWrappable.h"
+#include "platform/wtf/text/WTFString.h"
+
+namespace blink {
+
+// Implements the ScrollTimeline concept from the Scroll-linked Animations spec.

[alancutter (OOO until 2018), 2017/07/04 04:13:41]

It's worth adding the spec link here since it's directly mentioned.

[smcgruer, 2017/07/04 13:48:53]

Done.

+//
+// A ScrollTimeline is a special form of AnimationTimeline whose time values are
+// not determined by wall-clock time but instead the progress of scrolling in a
+// scroll container. The user is able to specify which scroll container to
+// track, the direction of scroll they care about, and various attributes to
+// control the conversion of scroll amount to time output.
+class CORE_EXPORT ScrollTimeline final : public AnimationTimeline {
+  DEFINE_WRAPPERTYPEINFO();
+
+ public:
+  enum ScrollDirection {
+    Block,
+    Inline,
+  };
+
+  static ScrollTimeline* Create(Document&,
+                                ScrollTimelineOptions,
+                                ExceptionState&);
+
+  // AnimationTimeline implementation.
+  double currentTime(bool& is_null) override;

[alancutter (OOO until 2018), 2017/07/04 04:13:41]

Let's use the final keyword here and save override to indicate that there's
other subclasses that override it further.

[smcgruer, 2017/07/04 13:48:53]

Done.

+
+  // IDL API implementation.
+  Element* scrollSource();
+  String orientation();
+  void timeRange(DoubleOrScrollTimelineAutoKeyword&);
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  ScrollTimeline(const Document&, Element*, ScrollDirection, double);
+
+  Member<Element> scroll_source_;
+  ScrollDirection orientation_;
+  double time_range_;
+};
+
+}  // namespace blink
+
+#endif