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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_ANCHOR_ELEMENT_METRICS_SENDER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_ANCHOR_ELEMENT_METRICS_SENDER_H_
#include "base/macros.h"
#include "third_party/blink/public/mojom/loader/navigation_predictor.mojom-blink.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/frame/local_frame_view.h"
#include "third_party/blink/renderer/platform/heap/handle.h"
#include "third_party/blink/renderer/platform/mojo/heap_mojo_remote.h"
#include "third_party/blink/renderer/platform/supplementable.h"
#include "third_party/blink/renderer/platform/wtf/hash_set.h"
#include "third_party/blink/renderer/platform/wtf/vector.h"
namespace blink {
class Document;
class HTMLAnchorElement;
class IntersectionObserver;
class IntersectionObserverEntry;
class AnchorElementMetrics;
// AnchorElementMetricsSender is responsible to send anchor element metrics to
// the browser process for a given document.
//
// The high level approach is:
// 1) When HTMLAnchorElements are inserted into the DOM,
// AnchorElementMetricsSender::AddAnchorElement is called and a reference to
// the element is stored. We also add the element to the intersection
// observer that watches for elements entering the viewport. The first time
// this happens, the sender is created, which registers itself for lifecycle
// callbacks.
// 2) If any elements enter the viewport, the intersection observer will call
// AnchorElementMetricsSender::UpdateVisibleAnchors. Elements are collected
// in entered_viewport_messages_ and will be reported after the next layout.
// 3) On the next layout, AnchorElementMetricsSender::DidFinishLifecycleUpdate
// is called, and it goes over the collected anchor elements. Elements that
// are visible are reported to the browser via ReportNewAnchorElements. The
// anchor elements collected in AnchorElementMetricsSender are all dropped.
// In particular, this drops elements that are not visible. They will never
// be reported even if they become visible later, unless the are reinserted
// into the DOM. This is not ideal, but simpler, keeps resource usage low,
// and seems to work well enough on the sites I've looked at. Also, elements
// that entered the viewport will be reported using
// ReportAnchorElementsEnteredViewport.
class CORE_EXPORT AnchorElementMetricsSender final
: public GarbageCollected<AnchorElementMetricsSender>,
public LocalFrameView::LifecycleNotificationObserver,
public Supplement<Document> {
public:
static const char kSupplementName[];
explicit AnchorElementMetricsSender(Document&);
virtual ~AnchorElementMetricsSender();
// LocalFrameView::LifecycleNotificationObserver
void WillStartLifecycleUpdate(const LocalFrameView&) override {}
void DidFinishLifecycleUpdate(
const LocalFrameView& local_frame_view) override;
// Returns the anchor element metrics sender of the root document of
// |Document|. Constructs new one if it does not exist.
static AnchorElementMetricsSender* From(Document&);
// Returns true if |document| should have associated
// AnchorElementMetricsSender.
static bool HasAnchorElementMetricsSender(Document& document);
// Report the link click to the browser process, so long as the anchor
// is an HTTP(S) link.
void MaybeReportClickedMetricsOnClick(
const HTMLAnchorElement& anchor_element);
// Adds an anchor element to |anchor_elements_|.
void AddAnchorElement(HTMLAnchorElement& element);
HeapMojoRemote<mojom::blink::AnchorElementMetricsHost>* MetricsHost();
// Creates AnchorElementMetrics from anchor element if possible. Then records
// the metrics, and sends them to the browser process.
void UpdateVisibleAnchors(
const HeapVector<Member<IntersectionObserverEntry>>& entries);
void Trace(Visitor*) const override;
private:
// Associates |metrics_host_| with the IPC interface if not already, so it can
// be used to send messages. Returns true if associated, false otherwise.
bool AssociateInterface();
// Creates an AnchorElementEnteredViewportPtr for the given element and
// enqueue it so that it gets reported after the next layout.
void EnqueueEnteredViewport(const HTMLAnchorElement& element);
// Use WeakMember to make sure we don't leak memory on long-lived pages.
HeapHashSet<WeakMember<HTMLAnchorElement>> anchor_elements_to_report_;
HeapMojoRemote<mojom::blink::AnchorElementMetricsHost> metrics_host_;
Member<IntersectionObserver> intersection_observer_;
WTF::Vector<mojom::blink::AnchorElementEnteredViewportPtr>
entered_viewport_messages_;
WTF::Vector<mojom::blink::AnchorElementClickPtr> clicked_messages_;
DISALLOW_COPY_AND_ASSIGN(AnchorElementMetricsSender);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_ANCHOR_ELEMENT_METRICS_SENDER_H_
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