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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_RESIZE_OBSERVER_RESIZE_OBSERVER_CONTROLLER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_RESIZE_OBSERVER_RESIZE_OBSERVER_CONTROLLER_H_
#include "third_party/blink/renderer/platform/heap/handle.h"
namespace blink {
class ResizeObserver;
// ResizeObserverController keeps track of all ResizeObservers
// in a single Document.
//
// The observation API is used to integrate ResizeObserver
// and the event loop. It delivers notification in a loop.
// In each iteration, only notifications deeper than the
// shallowest notification from previous iteration are delivered.
class ResizeObserverController final
: public GarbageCollected<ResizeObserverController> {
public:
static const size_t kDepthBottom = 4096;
ResizeObserverController();
void AddObserver(ResizeObserver&);
// observation API
// Returns depth of shallowest observed node, kDepthLimit if none.
size_t GatherObservations(size_t deeper_than);
// Returns true if gatherObservations has skipped observations
// because they were too shallow.
bool SkippedObservations();
void DeliverObservations();
void ClearObservations();
void ObserverChanged() { observers_changed_ = true; }
void Trace(blink::Visitor*);
// For testing only.
const HeapHashSet<WeakMember<ResizeObserver>>& Observers() {
return observers_;
}
private:
// Active observers
HeapHashSet<WeakMember<ResizeObserver>> observers_;
// True if any observers were changed since last notification.
bool observers_changed_;
};
} // namespace blink
#endif
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