Implement a site engagement score based on time-on-site.

chrome/browser/engagement/site_engagement_helper.cc

 // Copyright 2015 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.
 
 #include "chrome/browser/engagement/site_engagement_helper.h"
 
+#include "base/time/time.h"
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/engagement/site_engagement_service_factory.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/web_contents.h"
 
+namespace {
+
+double g_seconds_between_user_input_check = 10;
+bool g_disable_callback_registration_for_testing = false;
+
+}  // anonymous namespace
+
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(SiteEngagementHelper);
 
-SiteEngagementHelper::~SiteEngagementHelper() {
+SiteEngagementHelper::InputTracker::InputTracker(SiteEngagementHelper* helper)
+    : helper_(helper),
+      pause_timer_(new base::Timer(true, false)),
+      callbacks_added_(false) {
+  key_press_event_callback_ =
+      base::Bind(&SiteEngagementHelper::InputTracker::HandleKeyPressEvent,
+                 base::Unretained(this));
+  mouse_event_callback_ =
+      base::Bind(&SiteEngagementHelper::InputTracker::HandleMouseEvent,
+                 base::Unretained(this));
 }
 
-SiteEngagementHelper::SiteEngagementHelper(content::WebContents* web_contents)
-    : content::WebContentsObserver(web_contents) {
+SiteEngagementHelper::InputTracker::~InputTracker() { }
+
+// Record that there was some user input, and defer handling of the input event.
+// web_contents() will return nullptr if the observed contents have been
+// deleted; if the contents exist, record engagement for the site. Once the
+// timer finishes running, the callbacks detecting user input will be registered
+// again.
+bool SiteEngagementHelper::InputTracker::HandleKeyPressEvent(
+    const content::NativeWebKeyboardEvent& event) {
+  // Only respond to raw key down to avoid multiple triggering on a single input
+  // (e.g. keypress is a key down then key up).
+  if (event.type == blink::WebInputEvent::RawKeyDown) {
+    PauseTracking(helper_->web_contents()->GetRenderViewHost());
+    helper_->RecordUserInput();
+  }
+  return false;
 }
 
-void SiteEngagementHelper::DidStartNavigationToPendingEntry(
-    const GURL& url,
-    content::NavigationController::ReloadType reload_type) {
-  prerender::PrerenderContents* prerender_contents =
-      prerender::PrerenderContents::FromWebContents(web_contents());
+bool SiteEngagementHelper::InputTracker::HandleMouseEvent(
+    const blink::WebMouseEvent& event) {
+  // Only respond to mouse down with a button or mouse move events (e.g. a click
+  // is a mouse down and mouse up) to avoid cases where multiple events come in
+  // before we can pause tracking.
+  if ((event.button != blink::WebMouseEvent::ButtonNone &&
+       event.type == blink::WebInputEvent::MouseDown) ||
+      event.type == blink::WebInputEvent::MouseMove ||

[jdduke (slow), 2015/09/24 15:13:25]

I'm not sure MouseMove's without an active button should qualify as engagement
(on many platforms mousemoves are noisy and rapid). If the sampling here is
intentionally lossy and sparse (once per 10 seconds), just listening to a
mousedown is probably sufficient?

[dominickn, 2015/09/25 00:08:56]

Done, though I think it's also important to listen to wheel events here for the
case where people are reading a long document, and scrolling through it without
clicking or typing.

+      event.type == blink::WebInputEvent::MouseWheel) {
+    PauseTracking(helper_->web_contents()->GetRenderViewHost());
+    helper_->RecordUserInput();
+  }
+  return false;
+}
 
-  // Ignore pre-render loads.
-  if (prerender_contents != NULL)
-    return;
+void SiteEngagementHelper::InputTracker::StartTracking(
+    content::RenderViewHost* host) {
+  if (!callbacks_added_ && !g_disable_callback_registration_for_testing) {
+    host->AddKeyPressEventCallback(key_press_event_callback_);
+    host->AddMouseEventCallback(mouse_event_callback_);
+    callbacks_added_ = true;
+  }
+}
+
+void SiteEngagementHelper::InputTracker::PauseTracking(
+    content::RenderViewHost* host) {
+  StopTracking(host);
+  pause_timer_->Start(FROM_HERE, base::TimeDelta::FromSeconds(
+                               g_seconds_between_user_input_check),
+                base::Bind(&SiteEngagementHelper::InputTracker::ResumeTracking,
+                           base::Unretained(this)));
+}
+
+void SiteEngagementHelper::InputTracker::ResumeTracking() {
+  content::WebContents* contents = helper_->web_contents();
+  if (contents)
+    StartTracking(contents->GetRenderViewHost());
+}
+
+void SiteEngagementHelper::InputTracker::StopTracking(
+    content::RenderViewHost* host) {
+  pause_timer_->Stop();
+  if (callbacks_added_) {
+    host->RemoveKeyPressEventCallback(key_press_event_callback_);
+    host->RemoveMouseEventCallback(mouse_event_callback_);
+    callbacks_added_ = false;
+  }
+}
+
+void SiteEngagementHelper::InputTracker::SetTimerForTesting(
+    scoped_ptr<base::Timer> timer) {
+  pause_timer_ = timer.Pass();
+}
+
+SiteEngagementHelper::~SiteEngagementHelper() {
+  content::WebContents* contents = web_contents();
+  if (contents)
+    input_tracker_->StopTracking(contents->GetRenderViewHost());
+}
+
+void SiteEngagementHelper::AddObserverForTesting(Observer* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void SiteEngagementHelper::RemoveObserverForTesting(Observer* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
+SiteEngagementHelper::SiteEngagementHelper(content::WebContents* contents)
+    : content::WebContentsObserver(contents),
+      input_tracker_(new InputTracker(this)),
+      record_engagement_(false) { }
+
+void SiteEngagementHelper::RecordUserInput() {
+  content::WebContents* contents = web_contents();
+  if (contents) {
+    Profile* profile =
+        Profile::FromBrowserContext(contents->GetBrowserContext());
+    SiteEngagementService* service =
+        SiteEngagementServiceFactory::GetForProfile(profile);
+
+    // Service is null in incognito.
+    if (service) {
+      service->HandleUserInput(contents->GetVisibleURL());
+      FOR_EACH_OBSERVER(Observer, observer_list_, OnInputRecorded(this));

[jdduke (slow), 2015/09/24 15:17:35]

Any idea what the potential costs are here? Is it O(microseconds),
O(milliseconds)?

If it's potentially expensive could we add trace instrumentation for this
function?

[dominickn, 2015/09/25 00:08:56]

Do you mean the observer or the cost of recording user input? For the observer,
that's only used for testing.

There will be a follow-up CL posted today adding UMA metrics to try and work out
how often input is recorded, how quickly users accumulate engagement, and
whether we need adjust how often we're capturing input. These should hopefully
help us fine-tune what we're doing.

+    }
+  }
+}
+
+void SiteEngagementHelper::DidNavigateMainFrame(
+    const content::LoadCommittedDetails& details,
+    const content::FrameNavigateParams& params) {
+  content::WebContents* contents = web_contents();
+  input_tracker_->StopTracking(contents->GetRenderViewHost());
 
   // Ignore all schemes except HTTP and HTTPS.
-  if (!url.SchemeIsHTTPOrHTTPS())
+  record_engagement_ = params.url.SchemeIsHTTPOrHTTPS();
+
+  if (!record_engagement_)
     return;
 
   Profile* profile =
-      Profile::FromBrowserContext(web_contents()->GetBrowserContext());
+      Profile::FromBrowserContext(contents->GetBrowserContext());
   SiteEngagementService* service =
       SiteEngagementServiceFactory::GetForProfile(profile);
-  // Service is null in incognito.
-  if (!service)
-    return;
 
-  service->HandleNavigation(url);
+  if (service)
+    service->HandleNavigation(params.url, params.transition);
+
+  input_tracker_->StartTracking(contents->GetRenderViewHost());
 }
+
+void SiteEngagementHelper::RenderViewHostChanged(
+    content::RenderViewHost* old_host,
+    content::RenderViewHost* new_host) {
+  // On changing the render view host, we need to re-register the callbacks
+  // listening for user input.
+  if (record_engagement_) {
+    if (old_host)
+      input_tracker_->StopTracking(old_host);
+    input_tracker_->StartTracking(new_host);
+  }
+}
+
+void SiteEngagementHelper::WasShown() {
+  // Ensure that the input callbacks are registered when we come into view.
+  if (record_engagement_)
+    input_tracker_->StartTracking(web_contents()->GetRenderViewHost());
+}
+
+void SiteEngagementHelper::WasHidden() {
+  // Ensure that the input callbacks are not registered when hidden.
+  if (record_engagement_) {
+    content::WebContents* contents = web_contents();
+    if (contents)
+      input_tracker_->StopTracking(contents->GetRenderViewHost());
+  }
+}
+
+// static
+void SiteEngagementHelper::SetSecondsBetweenUserInputCheck(double seconds) {
+  g_seconds_between_user_input_check = seconds;
+}
+
+// static
+void SiteEngagementHelper::EnableCallbackRegistrationForTesting() {
+  g_disable_callback_registration_for_testing = false;
+}
+
+// static
+void SiteEngagementHelper::DisableCallbackRegistrationForTesting() {
+  g_disable_callback_registration_for_testing = true;
+}