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// Copyright 2018 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_HTML_LAZY_LOAD_IMAGE_OBSERVER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_LAZY_LOAD_IMAGE_OBSERVER_H_
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/heap/heap_allocator.h"
#include "third_party/blink/renderer/platform/heap/member.h"
namespace blink {
class Document;
class Element;
class HTMLImageElement;
class IntersectionObserver;
class IntersectionObserverEntry;
class Visitor;
class LazyLoadImageObserver final
: public GarbageCollected<LazyLoadImageObserver> {
public:
enum class DeferralMessage {
kNone,
kLoadEventsDeferred,
kMissingDimensionForLazy
};
struct VisibleLoadTimeMetrics {
// Keeps track of whether the image was initially intersecting the viewport.
bool is_initially_intersecting = false;
bool has_initial_intersection_been_set = false;
// Set when the image first becomes visible (i.e. appears in the viewport).
base::TimeTicks time_when_first_visible;
// Set when the first load event is dispatched for the image.
base::TimeTicks time_when_first_load_finished;
};
LazyLoadImageObserver(const Document&);
void StartMonitoringNearViewport(Document*, Element*, DeferralMessage);
void StopMonitoring(Element*);
void StartMonitoringVisibility(Document*, HTMLImageElement*);
void OnLoadFinished(HTMLImageElement*);
bool IsFullyLoadableFirstKImageAndDecrementCount();
void Trace(Visitor*) const;
private:
void LoadIfNearViewport(const HeapVector<Member<IntersectionObserverEntry>>&);
void OnVisibilityChanged(
const HeapVector<Member<IntersectionObserverEntry>>&);
// The intersection observer responsible for loading the image once it's near
// the viewport.
Member<IntersectionObserver> lazy_load_intersection_observer_;
// The intersection observer used to track when the image becomes visible.
Member<IntersectionObserver> visibility_metrics_observer_;
// Count of remaining images that can be fully loaded.
int count_remaining_images_fully_loaded_ = 0;
// Used to show the intervention console message one time only.
bool is_load_event_deferred_intervention_shown_ = false;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_LAZY_LOAD_IMAGE_OBSERVER_H_
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