chromium/third_party/blink/renderer/core/layout/anchor_position_visibility_observer.h

// Copyright 2024 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_LAYOUT_ANCHOR_POSITION_VISIBILITY_OBSERVER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_ANCHOR_POSITION_VISIBILITY_OBSERVER_H_

#include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_set.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_vector.h"
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/heap/member.h"
#include "third_party/blink/renderer/platform/heap/visitor.h"

namespace blink {

enum class LayerPositionVisibility : uint8_t;
class Element;
class IntersectionObserver;
class IntersectionObserverEntry;
class ScrollSnapshotClient;

// Monitors visibility of an anchor element for an anchored element, to support
// `position-visibility: anchors-visible` [1]. When the anchor is detected
// as newly-visible or newly-invisible, the anchored element's `PaintLayer` is
// updated via `PaintLayer::SetInvisibleForPositionVisibility`.
//
// There are two aspects of `anchors-visible` visibility:
// 1. Intersection, which is updated with a post-layout intersection observer
//    setup in `MonitorAnchor`.
// 2. CSS visibility, which is checked for all used anchors during all lifecycle
//    updates with `UpdateForCssAnchorVisibility`. This is needed to ensure we
//    catch CSS visibility changes on anchor elements.
//
// [1] Spec: https://drafts.csswg.org/css-anchor-position-1/#position-visibility
class AnchorPositionVisibilityObserver final
    : public GarbageCollected<AnchorPositionVisibilityObserver> { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_ANCHOR_POSITION_VISIBILITY_OBSERVER_H_