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// 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.
#include "base/optional.h"
#include "cc/animation/animation_export.h"
#include "cc/trees/element_id.h"
namespace cc {
class ScrollTree;
// A ScrollTimeline is an animation timeline that bases its current time on the
// progress of scrolling in some scroll container.
// This is the compositor-side representation of the web concept expressed in
// There are
// differences between this class and the web definition of a ScrollTimeline.
// For example the compositor does not know (or care) about 'writing modes', so
// this class only tracks whether the ScrollTimeline orientation is horizontal
// or vertical. Blink is expected to resolve any such 'web' requirements and
// construct/update the compositor ScrollTimeline accordingly.
class CC_ANIMATION_EXPORT ScrollTimeline {
enum ScrollDirection { Horizontal, Vertical };
ScrollTimeline(base::Optional<ElementId> scroller_id,
ScrollDirection orientation,
base::Optional<double> start_scroll_offset,
base::Optional<double> end_scroll_offset,
double time_range);
virtual ~ScrollTimeline();
// Create a copy of this ScrollTimeline intended for the impl thread in the
// compositor.
std::unique_ptr<ScrollTimeline> CreateImplInstance() const;
// Calculate the current time of the ScrollTimeline. This is either a double
// value or std::numeric_limits<double>::quiet_NaN() if the current time is
// unresolved.
virtual double CurrentTime(const ScrollTree& scroll_tree,
bool is_active_tree) const;
void SetScrollerId(base::Optional<ElementId> scroller_id);
void UpdateStartAndEndScrollOffsets(
base::Optional<double> start_scroll_offset,
base::Optional<double> end_scroll_offset);
void PushPropertiesTo(ScrollTimeline* impl_timeline);
void PromoteScrollTimelinePendingToActive();
// The scroller which this ScrollTimeline is based on. The same underlying
// scroll source may have different ids in the pending and active tree (see
base::Optional<ElementId> active_id_;
base::Optional<ElementId> pending_id_;
// The orientation of the ScrollTimeline indicates which axis of the scroller
// it should base its current time on - either the horizontal or vertical.
ScrollDirection orientation_;
base::Optional<double> start_scroll_offset_;
base::Optional<double> end_scroll_offset_;
// A ScrollTimeline maps from the scroll offset in the scroller to a time
// value based on a 'time range'. See the implementation of CurrentTime or the
// spec for details.
double time_range_;
} // namespace cc