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// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_TIMELINE_RANGE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_TIMELINE_RANGE_H_
#include "cc/animation/scroll_timeline.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_timeline_range.h"
#include "third_party/blink/renderer/core/core_export.h"
namespace blink {
struct TimelineOffset;
// A TimelineRange represents a given scroll range within an associated
// scroller's minimum/maximum scroll. This is useful for ViewTimelines
// in particular, because they represent exactly that: a segment of a (non-view)
// ScrollTimeline.
//
// The primary job of TimelineRange is to convert offsets within an animation
// attachment range [1] (represented by TimelineOffset values) to fractional
// offsets within the TimelineRange. See TimelineRange::ToFractionalOffset.
//
// It may be helpful to think about a TimelineRange (which is timeline-specific)
// as a sub-range of the scroller's full range, and an animation attachment
// range (which is animation specific) as a sub-range of that TimelineRange.
//
// - For ViewTimelines, the start/end offsets will correspond to the scroll
// range that would cause the scrollport to intersect with the subject
// element's box.
// - For (non-view) ScrollTimelines, the start/end offset is always the
// same as the minimum/maximum scroll.
// - For monotonic timelines, the TimelineRange is always empty.
//
// [1]
// https://drafts.csswg.org/scroll-animations-1/#named-range-animation-declaration
class CORE_EXPORT TimelineRange {
public:
using ScrollOffsets = cc::ScrollTimeline::ScrollOffsets;
using NamedRange = V8TimelineRange::Enum;
// For a view timeline, stores the distances of 'entry-crossing' and
// 'exit-crossing' ranges.
// Note that 'cover' is in TimelineRange::offsets_, and 'contain' and others
// can be inferred (see TimelineRange::ConvertNamedRange). Usually, entry and
// exit distance correspond to the layout size of the subject, but may differ
// with position:sticky (crbug.com/1448294).
struct ViewOffsets {
ViewOffsets() = default;
ViewOffsets(double entry, double exit) {
entry_crossing_distance = entry;
exit_crossing_distance = exit;
}
bool operator==(const ViewOffsets& other) const {
return entry_crossing_distance == other.entry_crossing_distance &&
exit_crossing_distance == other.exit_crossing_distance;
}
bool operator!=(const ViewOffsets& other) const {
return !(*this == other);
}
double entry_crossing_distance = 0;
double exit_crossing_distance = 0;
};
TimelineRange() = default;
// The `limits` parameter represents the full scroll range,
// and `offsets` a segment of that range. (See class description.)
explicit TimelineRange(ScrollOffsets limits,
ScrollOffsets offsets,
ViewOffsets view_offsets)
: scroll_limits_(limits),
offsets_(offsets),
view_offsets_(view_offsets) {}
bool operator==(const TimelineRange& other) const {
return offsets_ == other.offsets_ && view_offsets_ == other.view_offsets_ &&
scroll_limits_ == other.scroll_limits_;
}
bool operator!=(const TimelineRange& other) const {
return !(*this == other);
}
bool IsEmpty() const;
// Converts an offset within some animation attachment range to a fractional
// offset within this TimelineRange.
double ToFractionalOffset(const TimelineOffset&) const;
private:
// https://drafts.csswg.org/scroll-animations-1/#view-timelines-ranges
ScrollOffsets ConvertNamedRange(NamedRange) const;
// Scroll offsets corresponding to the entire scroll range of the scroll
// container backing the timeline in the axis of the timeline.
// For a ScrollTimeline, it is the same as |offsets_|.
ScrollOffsets scroll_limits_;
// For a ScrollTimeline: this corresponds to the entire scroll range of the
// scroll container backing the timeline and is the same as |scroll_limits_|.
// For a ViewTimeline: this corresponds to the boundaries of the view progress
// of the subject within the scroll container backing the timeline. It is a
// segment of |scroll_limits_|.
ScrollOffsets offsets_;
ViewOffsets view_offsets_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_ANIMATION_TIMELINE_RANGE_H_
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