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// Copyright 2016 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 THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_SCROLLING_SNAP_COORDINATOR_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_SCROLLING_SNAP_COORDINATOR_H_
#include "base/macros.h"
#include "cc/input/scroll_snap_data.h"
#include "cc/input/snap_selection_strategy.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/css/css_primitive_value_mappings.h"
#include "third_party/blink/renderer/platform/heap/handle.h"
namespace blink {
class LayoutBox;
// Snap Coordinator keeps track of snap containers and all of their associated
// snap areas. It also contains the logic to generate the list of valid snap
// positions for a given snap container.
//
// Snap container:
// An scroll container that has 'scroll-snap-type' value other
// than 'none'.
// Snap area:
// A snap container's descendant that contributes snap positions. An element
// only contributes snap positions to its nearest ancestor (on the element’s
// containing block chain) scroll container.
//
// For more information see spec: https://drafts.csswg.org/css-snappoints/
class CORE_EXPORT SnapCoordinator final
: public GarbageCollectedFinalized<SnapCoordinator> {
public:
explicit SnapCoordinator();
~SnapCoordinator();
void Trace(blink::Visitor* visitor) {}
void SnapContainerDidChange(LayoutBox&, bool is_removed);
void SnapAreaDidChange(LayoutBox&, cc::ScrollSnapAlign);
// Returns the SnapContainerData if the snap container has one.
base::Optional<cc::SnapContainerData> GetSnapContainerData(
const LayoutBox& snap_container) const;
// Calculate the SnapAreaData for the specific snap area in its snap
// container.
cc::SnapAreaData CalculateSnapAreaData(const LayoutBox& snap_area,
const LayoutBox& snap_container);
// Called by LocalFrameView::PerformPostLayoutTasks(), so that the snap data
// are updated whenever a layout happens.
void UpdateAllSnapContainerData();
// SnapAtCurrentPosition(), SnapForEndPosition(), SnapForDirection(), and
// SnapForEndAndDirection() return true if snapping was performed, and false
// otherwise.
// SnapAtCurrentPosition() calls SnapForEndPosition() with the current scroll
// position.
bool SnapAtCurrentPosition(const LayoutBox& snap_container,
bool scrolled_x,
bool scrolled_y) const;
bool SnapForEndPosition(const LayoutBox& snap_container,
const FloatPoint& end_position,
bool scrolled_x,
bool scrolled_y) const;
bool SnapForDirection(const LayoutBox& snap_container,
const ScrollOffset& delta) const;
bool SnapForEndAndDirection(const LayoutBox& snap_container,
const ScrollOffset& delta) const;
base::Optional<FloatPoint> GetSnapPosition(
const LayoutBox& snap_container,
const cc::SnapSelectionStrategy& strategy) const;
#ifndef NDEBUG
void ShowSnapAreaMap();
void ShowSnapAreasFor(const LayoutBox*);
void ShowSnapDataFor(const LayoutBox*);
#endif
private:
friend class SnapCoordinatorTest;
bool PerformSnapping(const LayoutBox& snap_container,
const cc::SnapSelectionStrategy& strategy) const;
void UpdateSnapContainerData(LayoutBox&);
HashMap<LayoutBox*, cc::SnapContainerData> snap_container_map_;
DISALLOW_COPY_AND_ASSIGN(SnapCoordinator);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_SCROLLING_SNAP_COORDINATOR_H_
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