cast: Support for low-latency interactive mode

content/browser/media/capture/window_activity_tracker_aura.cc

+// Copyright (c) 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 "content/browser/media/capture/window_activity_tracker_aura.h"
+
+#include "base/logging.h"
+#include "ui/aura/window.h"
+#include "ui/aura/window_tree_host.h"
+#include "ui/events/event_utils.h"
+
+namespace content {
+
+namespace {
+// The time period within which a triggered UI event is considered
+// currently active.
+const int kTimePeriodUiEventMicros = 100000;  // 100 ms
+
+// Minimum number of user interactions before we consider the user to be in
+// interactive mode. The goal is to prevent user interactions to launch
+// animated content from causing target playout time flip-flop.
+const int kMinUserInteractions = 5;
+}  // namespace
+
+WindowActivityTrackerAura::WindowActivityTrackerAura(aura::Window* window)
+    : window_(window),
+      last_time_ui_event_detected_(base::TimeTicks()),
+      ui_events_count_(0),
+      weak_factory_(this) {
+  if (window_) {
+    window_->AddObserver(this);
+    window_->AddPreTargetHandler(this);
+  }
+}
+
+WindowActivityTrackerAura::~WindowActivityTrackerAura() {
+  if (window_) {
+    window_->RemoveObserver(this);
+    window_->RemovePreTargetHandler(this);
+  }
+}
+
+base::WeakPtr<WindowActivityTracker> WindowActivityTrackerAura::GetWeakPtr() {
+  return weak_factory_.GetWeakPtr();
+}
+
+bool WindowActivityTrackerAura::IsUiInteractionActive() const {
+  return ui_events_count_ > kMinUserInteractions;
+}
+
+void WindowActivityTrackerAura::Reset() {
+  ui_events_count_ = 0;
+  last_time_ui_event_detected_ = base::TimeTicks();
+}
+
+void WindowActivityTrackerAura::OnEvent(ui::Event* event) {
+  if (base::TimeTicks::Now() - last_time_ui_event_detected_ >
+      base::TimeDelta::FromMicroseconds(kTimePeriodUiEventMicros)) {
+    ui_events_count_++;
+  }
+  last_time_ui_event_detected_ = base::TimeTicks::Now();
+}
+
+void WindowActivityTrackerAura::OnWindowDestroying(aura::Window* window) {
+  DCHECK_EQ(window_, window);
+  window_->RemovePreTargetHandler(this);
+  window_->RemoveObserver(this);
+  window_ = nullptr;
+}
+
+}  // namespace content