Adds the UserInputMonitor implementation for Windows.

media/base/user_input_monitor_linux.cc

Index: media/base/user_input_monitor_linux.cc
diff --git a/media/base/user_input_monitor_linux.cc b/media/base/user_input_monitor_linux.cc
index 196b4e7407836319eb72af8b5298d0aebf84bc8e..3b80f4b869bd656ffe853c22a4c1f8890a4785e0 100644
--- a/media/base/user_input_monitor_linux.cc
+++ b/media/base/user_input_monitor_linux.cc
@@ -15,10 +15,13 @@
 #include "base/compiler_specific.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/message_loop/message_pump_libevent.h"
+#include "base/observer_list_threadsafe.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/single_thread_task_runner.h"
+#include "base/synchronization/lock.h"
 #include "media/base/keyboard_event_counter.h"
 #include "third_party/skia/include/core/SkPoint.h"
 #include "ui/base/keycodes/keyboard_code_conversion_x.h"
@@ -32,32 +35,32 @@
 namespace media {
 namespace {
 
-class UserInputMonitorLinux : public UserInputMonitor ,
-                              public base::MessagePumpLibevent::Watcher {
+// This is the actual implementation of event monitoring. It's separated from
+// UserInputMonitorLinux since it needs to be deleted on the IO thread.
+class UserInputMonitorLinuxCore : public base::MessagePumpLibevent::Watcher {
  public:
-  explicit UserInputMonitorLinux(
-      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
-  virtual ~UserInputMonitorLinux();
-
-  virtual size_t GetKeyPressCount() const OVERRIDE;
-
- private:
   enum EventType {
     MOUSE_EVENT,
     KEYBOARD_EVENT
   };
 
-  virtual void StartMouseMonitoring() OVERRIDE;
-  virtual void StopMouseMonitoring() OVERRIDE;
-  virtual void StartKeyboardMonitoring() OVERRIDE;
-  virtual void StopKeyboardMonitoring() OVERRIDE;
+  explicit UserInputMonitorLinuxCore(
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+  virtual ~UserInputMonitorLinuxCore();
 
-  //
-  // The following methods must be called on the IO thread.
-  //
+  void AddMouseListener(UserInputMonitor::MouseEventListener* listener);
+  void RemoveMouseListener(UserInputMonitor::MouseEventListener* listener);
+  size_t GetKeyPressCount() const;
   void StartMonitor(EventType type);
   void StopMonitor(EventType type);
 
+  base::WeakPtr<UserInputMonitorLinuxCore> GetWeakPtr() {
+    return weak_factory_.GetWeakPtr();

[Wez, 2013/09/11 08:03:42]

You can avoid this ugly WeakPtr getter by keeping the |weak_factory_| in
UserInputMonitor and posting the OnMouseListenerAdded/Removed() tasks from its
Add/RemoveMouseListener() methods.

You just have to remember to |weak_factory_.Invalidate()| in ~UserInputMonitor()
before you call DeleteSoon() on the core.

[jiayl, 2013/09/11 16:57:10]

To reiterate why PostTask to IO thread from UserInputMonitor will not work:
1. the listener list has to live in Core so that Core does not need to callback
to UserInputMonitor. Calling back to UserInputMonitor is problematic because
WeakPtr does not work across threads (i.e. UserInputMonitor will be deref'd on
IO thread but invalidated on UI thread) and we don't want to add ref counting
for UserInputMonitor.
2. Because of #1, Core is responsible to update the listener list. It has to
happen on the calling thread, since the caller may destroy the listener
immediately after calling RemoveListener. So we cannot PostTask to IO thread
from UserInputMonitor.

[Wez, 2013/09/13 10:01:27]

You could add the listener from UserInputMonitor, though, before posting the
task.

It'd mean providing a scoped_refptr<> mouse_listeners() getter for
UserInputMonitor to use, but since Core is an internal implementation detail,
that seems reasonable, and it saves the boilerplate Add/RemoveMouseListener()
and GetWeakPtr() calls on Core.

You'd need to re-instate the Lock around the mouse counter updates for that to
work, but since that's how keyboard is handled, that doesn't seem unreasonable.

+  }
+
+ private:
+  void OnMouseListenerAdded();
+  void OnMouseListenerRemoved();
   // base::MessagePumpLibevent::Watcher interface.
   virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
   virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
@@ -66,93 +69,94 @@ class UserInputMonitorLinux : public UserInputMonitor ,
   void ProcessXEvent(xEvent* event);
   static void ProcessReply(XPointer self, XRecordInterceptData* data);
 
-  // Task runner on which X Window events are received.
   scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+  scoped_refptr<ObserverListThreadSafe<UserInputMonitor::MouseEventListener> >
+      mouse_listeners_;
 
   //
   // The following members should only be accessed on the IO thread.
   //
+  size_t mouse_listeners_count_;
   base::MessagePumpLibevent::FileDescriptorWatcher controller_;
-  Display* display_;
+  Display* x_control_display_;
   Display* x_record_display_;
   XRecordRange* x_record_range_[2];
   XRecordContext x_record_context_;
   KeyboardEventCounter counter_;
+  base::WeakPtrFactory<UserInputMonitorLinuxCore> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(UserInputMonitorLinuxCore);
+};
+
+class UserInputMonitorLinux : public UserInputMonitor {
+ public:
+  explicit UserInputMonitorLinux(
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+  virtual ~UserInputMonitorLinux();
+
+  // Public UserInputMonitor overrides.
+  virtual void AddMouseListener(MouseEventListener* listener) OVERRIDE;
+  virtual void RemoveMouseListener(MouseEventListener* listener) OVERRIDE;
+  virtual size_t GetKeyPressCount() const OVERRIDE;
+
+ private:
+  // Private UserInputMonitor overrides.
+  virtual void StartKeyboardMonitoring() OVERRIDE;
+  virtual void StopKeyboardMonitoring() OVERRIDE;
+
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+  UserInputMonitorLinuxCore* core_;
 
   DISALLOW_COPY_AND_ASSIGN(UserInputMonitorLinux);
 };
 
-UserInputMonitorLinux::UserInputMonitorLinux(
+UserInputMonitorLinuxCore::UserInputMonitorLinuxCore(
     const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner)
     : io_task_runner_(io_task_runner),
-      display_(NULL),
+      mouse_listeners_(
+          new ObserverListThreadSafe<UserInputMonitor::MouseEventListener>()),
+      mouse_listeners_count_(0),
+      x_control_display_(NULL),
       x_record_display_(NULL),
-      x_record_context_(0) {
+      x_record_context_(0),
+      weak_factory_(this) {
   x_record_range_[0] = NULL;
   x_record_range_[1] = NULL;
 }
 
-UserInputMonitorLinux::~UserInputMonitorLinux() {
-  DCHECK(!display_);
+UserInputMonitorLinuxCore::~UserInputMonitorLinuxCore() {
+  DCHECK_EQ(0u, mouse_listeners_count_);
+  mouse_listeners_->AssertEmpty();
+  DCHECK(!x_control_display_);
   DCHECK(!x_record_display_);
   DCHECK(!x_record_range_[0]);
   DCHECK(!x_record_range_[1]);
   DCHECK(!x_record_context_);
 }
 
-size_t UserInputMonitorLinux::GetKeyPressCount() const {
-  return counter_.GetKeyPressCount();
-}
-
-void UserInputMonitorLinux::StartMouseMonitoring() {
-  if (!io_task_runner_->BelongsToCurrentThread()) {
-    io_task_runner_->PostTask(
-        FROM_HERE,
-        base::Bind(&UserInputMonitorLinux::StartMonitor,
-                   base::Unretained(this),
-                   MOUSE_EVENT));
-    return;
-  }
-  StartMonitor(MOUSE_EVENT);
-}
-
-void UserInputMonitorLinux::StopMouseMonitoring() {
-  if (!io_task_runner_->BelongsToCurrentThread()) {
-    io_task_runner_->PostTask(
-        FROM_HERE,
-        base::Bind(&UserInputMonitorLinux::StopMonitor,
-                   base::Unretained(this),
-                   MOUSE_EVENT));
-    return;
-  }
-  StopMonitor(MOUSE_EVENT);
+void UserInputMonitorLinuxCore::AddMouseListener(
+    UserInputMonitor::MouseEventListener* listener) {
+  mouse_listeners_->AddObserver(listener);
+  io_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&UserInputMonitorLinuxCore::OnMouseListenerAdded,
+                 weak_factory_.GetWeakPtr()));
 }
 
-void UserInputMonitorLinux::StartKeyboardMonitoring() {
-  if (!io_task_runner_->BelongsToCurrentThread()) {
-    io_task_runner_->PostTask(
-        FROM_HERE,
-        base::Bind(&UserInputMonitorLinux::StartMonitor,
-                   base::Unretained(this),
-                   KEYBOARD_EVENT));
-    return;
-  }
-  StartMonitor(KEYBOARD_EVENT);
+void UserInputMonitorLinuxCore::RemoveMouseListener(
+    UserInputMonitor::MouseEventListener* listener) {
+  mouse_listeners_->RemoveObserver(listener);
+  io_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&UserInputMonitorLinuxCore::OnMouseListenerRemoved,
+                 weak_factory_.GetWeakPtr()));
 }
 
-void UserInputMonitorLinux::StopKeyboardMonitoring() {
-  if (!io_task_runner_->BelongsToCurrentThread()) {
-    io_task_runner_->PostTask(
-        FROM_HERE,
-        base::Bind(&UserInputMonitorLinux::StopMonitor,
-                   base::Unretained(this),
-                   KEYBOARD_EVENT));
-    return;
-  }
-  StopMonitor(KEYBOARD_EVENT);
+size_t UserInputMonitorLinuxCore::GetKeyPressCount() const {
+  return counter_.GetKeyPressCount();
 }
 
-void UserInputMonitorLinux::StartMonitor(EventType type) {
+void UserInputMonitorLinuxCore::StartMonitor(EventType type) {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
 
   if (type == KEYBOARD_EVENT)
@@ -163,19 +167,20 @@ void UserInputMonitorLinux::StartMonitor(EventType type) {
   // and both channels are used from a separate thread, we'll need to duplicate
   // them with something like the following:
   //   XOpenDisplay(DisplayString(display));
-  if (!display_)
-    display_ = XOpenDisplay(NULL);
+  if (!x_control_display_)
+    x_control_display_ = XOpenDisplay(NULL);
 
   if (!x_record_display_)
     x_record_display_ = XOpenDisplay(NULL);
 
-  if (!display_ || !x_record_display_) {
+  if (!x_control_display_ || !x_record_display_) {
     LOG(ERROR) << "Couldn't open X display";
     return;
   }
 
   int xr_opcode, xr_event, xr_error;
-  if (!XQueryExtension(display_, "RECORD", &xr_opcode, &xr_event, &xr_error)) {
+  if (!XQueryExtension(
+           x_control_display_, "RECORD", &xr_opcode, &xr_event, &xr_error)) {
     LOG(ERROR) << "X Record extension not available.";
     return;
   }
@@ -198,8 +203,8 @@ void UserInputMonitorLinux::StartMonitor(EventType type) {
   }
 
   if (x_record_context_) {
-    XRecordDisableContext(display_, x_record_context_);
-    XFlush(display_);
+    XRecordDisableContext(x_control_display_, x_record_context_);
+    XFlush(x_control_display_);
     XRecordFreeContext(x_record_display_, x_record_context_);
     x_record_context_ = 0;
   }
@@ -222,7 +227,7 @@ void UserInputMonitorLinux::StartMonitor(EventType type) {
 
   if (!XRecordEnableContextAsync(x_record_display_,
                                  x_record_context_,
-                                 &UserInputMonitorLinux::ProcessReply,
+                                 &UserInputMonitorLinuxCore::ProcessReply,
                                  reinterpret_cast<XPointer>(this))) {
     LOG(ERROR) << "XRecordEnableContextAsync failed.";
     return;
@@ -248,7 +253,7 @@ void UserInputMonitorLinux::StartMonitor(EventType type) {
   OnFileCanReadWithoutBlocking(ConnectionNumber(x_record_display_));
 }
 
-void UserInputMonitorLinux::StopMonitor(EventType type) {
+void UserInputMonitorLinuxCore::StopMonitor(EventType type) {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
 
   if (x_record_range_[type]) {
@@ -261,8 +266,8 @@ void UserInputMonitorLinux::StopMonitor(EventType type) {
   // Context must be disabled via the control channel because we can't send
   // any X protocol traffic over the data channel while it's recording.
   if (x_record_context_) {
-    XRecordDisableContext(display_, x_record_context_);
-    XFlush(display_);
+    XRecordDisableContext(x_control_display_, x_record_context_);
+    XFlush(x_control_display_);
     XRecordFreeContext(x_record_display_, x_record_context_);
     x_record_context_ = 0;
 
@@ -271,14 +276,32 @@ void UserInputMonitorLinux::StopMonitor(EventType type) {
       XCloseDisplay(x_record_display_);
       x_record_display_ = NULL;
     }
-    if (display_) {
-      XCloseDisplay(display_);
-      display_ = NULL;
+    if (x_control_display_) {
+      XCloseDisplay(x_control_display_);
+      x_control_display_ = NULL;
     }
   }
 }
 
-void UserInputMonitorLinux::OnFileCanReadWithoutBlocking(int fd) {
+void UserInputMonitorLinuxCore::OnMouseListenerAdded() {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+  mouse_listeners_count_++;
+  if (mouse_listeners_count_ == 1) {
+    StartMonitor(MOUSE_EVENT);
+    DVLOG(2) << "Started mouse monitoring.";
+  }
+}
+
+void UserInputMonitorLinuxCore::OnMouseListenerRemoved() {
+  DCHECK(io_task_runner_->BelongsToCurrentThread());
+  mouse_listeners_count_--;
+  if (mouse_listeners_count_ == 0) {
+    StopMonitor(MOUSE_EVENT);
+    DVLOG(2) << "Stopped mouse monitoring.";
+  }
+}
+
+void UserInputMonitorLinuxCore::OnFileCanReadWithoutBlocking(int fd) {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
   XEvent event;
   // Fetch pending events if any.
@@ -287,16 +310,17 @@ void UserInputMonitorLinux::OnFileCanReadWithoutBlocking(int fd) {
   }
 }
 
-void UserInputMonitorLinux::OnFileCanWriteWithoutBlocking(int fd) {
+void UserInputMonitorLinuxCore::OnFileCanWriteWithoutBlocking(int fd) {
   NOTREACHED();
 }
 
-void UserInputMonitorLinux::ProcessXEvent(xEvent* event) {
+void UserInputMonitorLinuxCore::ProcessXEvent(xEvent* event) {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
   if (event->u.u.type == MotionNotify) {
     SkIPoint position(SkIPoint::Make(event->u.keyButtonPointer.rootX,
                                      event->u.keyButtonPointer.rootY));
-    OnMouseEvent(position);
+    mouse_listeners_->Notify(
+        &UserInputMonitor::MouseEventListener::OnMouseMoved, position);
   } else {
     ui::EventType type;
     if (event->u.u.type == KeyPress) {
@@ -308,22 +332,65 @@ void UserInputMonitorLinux::ProcessXEvent(xEvent* event) {
       return;
     }
 
-    KeySym key_sym = XkbKeycodeToKeysym(display_, event->u.u.detail, 0, 0);
+    KeySym key_sym =
+        XkbKeycodeToKeysym(x_control_display_, event->u.u.detail, 0, 0);
     ui::KeyboardCode key_code = ui::KeyboardCodeFromXKeysym(key_sym);
     counter_.OnKeyboardEvent(type, key_code);
   }
 }
 
 // static
-void UserInputMonitorLinux::ProcessReply(XPointer self,
-                                         XRecordInterceptData* data) {
+void UserInputMonitorLinuxCore::ProcessReply(XPointer self,
+                                             XRecordInterceptData* data) {
   if (data->category == XRecordFromServer) {
     xEvent* event = reinterpret_cast<xEvent*>(data->data);
-    reinterpret_cast<UserInputMonitorLinux*>(self)->ProcessXEvent(event);
+    reinterpret_cast<UserInputMonitorLinuxCore*>(self)->ProcessXEvent(event);
   }
   XRecordFreeData(data);
 }
 
+//
+// Implementation of UserInputMonitorLinux.
+//
+
+UserInputMonitorLinux::UserInputMonitorLinux(
+    const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner)
+    : io_task_runner_(io_task_runner),
+      core_(new UserInputMonitorLinuxCore(io_task_runner)) {}
+
+UserInputMonitorLinux::~UserInputMonitorLinux() {
+  if (!io_task_runner_->DeleteSoon(FROM_HERE, core_))
+    delete core_;
+}
+
+void UserInputMonitorLinux::AddMouseListener(MouseEventListener* listener) {
+  core_->AddMouseListener(listener);
+}
+
+void UserInputMonitorLinux::RemoveMouseListener(MouseEventListener* listener) {
+  core_->RemoveMouseListener(listener);
+}
+
+size_t UserInputMonitorLinux::GetKeyPressCount() const {
+  return core_->GetKeyPressCount();
+}
+
+void UserInputMonitorLinux::StartKeyboardMonitoring() {
+  io_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&UserInputMonitorLinuxCore::StartMonitor,
+                 core_->GetWeakPtr(),
+                 UserInputMonitorLinuxCore::KEYBOARD_EVENT));
+}
+
+void UserInputMonitorLinux::StopKeyboardMonitoring() {
+  io_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&UserInputMonitorLinuxCore::StopMonitor,
+                 core_->GetWeakPtr(),
+                 UserInputMonitorLinuxCore::KEYBOARD_EVENT));
+}
+
 }  // namespace
 
 scoped_ptr<UserInputMonitor> UserInputMonitor::Create(