Adding key press detection in the browser process.

media/base/user_input_monitor.h

+// Copyright 2013 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 MEDIA_BASE_USER_INPUT_MONITOR_H_
+#define MEDIA_BASE_USER_INPUT_MONITOR_H_
+
+#include <set>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "base/synchronization/lock.h"
+#include "media/base/media_export.h"
+#include "ui/base/events/event_constants.h"
+#include "ui/base/keycodes/keyboard_codes.h"
+
+struct SkIPoint;
+
+namespace base {
+class SingleThreadTaskRunner;
+}  // namespace base
+
+namespace media {
+
+// Monitors and notifies about mouse movements and keyboard events.
+// Thread safe. The thread on which the listenters are called is not guaranteed.
+// The callers should not perform expensive/blocking tasks in the callback since
+// it might be called on the browser UI/IO threads.
+class MEDIA_EXPORT UserInputMonitor {
+ public:
+  // The interface to receive mouse movement events.
+  class MEDIA_EXPORT MouseEventListener {
+   public:
+    // |position| is the new mouse position.
+    virtual void OnMouseMoved(const SkIPoint& position) = 0;
+
+   protected:
+    virtual ~MouseEventListener() {}
+  };
+  // The interface to receive key stroke events.
+  class MEDIA_EXPORT KeyStrokeListener {
+   public:
+    // Called when any key is pressed. Called only once until the key is
+    // released, i.e. holding down a key for a long period will generate one
+    // callback just when the key is pressed down.
+    virtual void OnKeyStroke() = 0;
+
+   protected:
+    virtual ~KeyStrokeListener() {}
+  };
+
+  virtual ~UserInputMonitor();
+
+  // Creates a platform-specific instance of UserInputMonitor.
+  // |io_task_runner| is the task runner for an IO thread.
+  // |ui_task_runner| is the task runner for a UI thread.
+  static scoped_ptr<UserInputMonitor> Create(
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner,
+      const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner);
+
+  // The same |listener| should only be added once.
+  // The clients should make sure to call Remove*Listener before |listener| is
+  // destroyed.
+  void AddMouseListener(MouseEventListener* listener);
+  void RemoveMouseListener(MouseEventListener* listener);
+  void AddKeyStrokeListener(KeyStrokeListener* listener);
+  void RemoveKeyStrokeListener(KeyStrokeListener* listener);
+
+ protected:
+  UserInputMonitor();
+
+  // Called by the platform-specific sub-classes to propagate the events to the
+  // listeners.
+  void OnMouseEvent(const SkIPoint& position);
+  void OnKeyboardEvent(ui::EventType event, ui::KeyboardCode key_code);
+
+ private:
+  virtual void StartMouseMonitoring() = 0;
+  virtual void StopMouseMonitoring() = 0;
+  virtual void StartKeyboardMonitoring() = 0;
+  virtual void StopKeyboardMonitoring() = 0;
+
+  base::Lock lock_;
+  ObserverList<MouseEventListener, true> mouse_listeners_;
+  ObserverList<KeyStrokeListener, true> key_stroke_listeners_;
+  bool monitoring_mouse_;
+  bool monitoring_keyboard_;
+  // The set of keys currently held down. Used for convering raw keyboard events
+  // into KeyStrokeListener callbacks.
+  std::set<ui::KeyboardCode> pressed_keys_;
+
+  DISALLOW_COPY_AND_ASSIGN(UserInputMonitor);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_USER_INPUT_MONITOR_H_