Add a ChromeOS implementation of VideoCaptureDevice

media/video/capture/linux/video_capture_device_chromeos.cc

+// Copyright 2014 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 "media/video/capture/linux/video_capture_device_chromeos.h"
+
+#include "base/bind.h"
+#include "base/memory/ref_counted.h"
+#include "ui/gfx/display.h"
+#include "ui/gfx/display_observer.h"
+#include "ui/gfx/screen.h"
+
+namespace media {
+
+// This is a delegate class used to transfer Display change events from the UI
+// thread to the media thread.
+class VideoCaptureDeviceChromeOS::ScreenObserverDelegate
+    : public gfx::DisplayObserver,
+      public base::RefCountedThreadSafe<ScreenObserverDelegate> {
+ public:
+  ScreenObserverDelegate(VideoCaptureDeviceChromeOS* capture_device)
+      : capture_device_(capture_device),
+        capture_thread_loop_(base::MessageLoop::current()) {
+    base::MessageLoopForUI::current()->PostTask(
+      FROM_HERE,

[perkj_chrome, 2014/05/13 09:46:40]

nit: indentation

[Zachary Kuznia, 2014/05/13 13:54:29]

Done.

+      base::Bind(&ScreenObserverDelegate::AddObserverOnUIThread, this));
+  }
+
+  void RemoveObserver() {
+    DCHECK(capture_thread_loop_ == base::MessageLoop::current());
+    capture_device_ = NULL;
+    base::MessageLoopForUI::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&ScreenObserverDelegate::RemoveObserverOnUIThread, this));
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<ScreenObserverDelegate>;
+
+  virtual ~ScreenObserverDelegate() {
+    DCHECK(!capture_device_);
+  }
+
+  // gfx::DisplayObserver:
+  virtual void OnDisplayBoundsChanged(const gfx::Display& display) OVERRIDE {
+    SendDisplayRotation(display);
+  }
+
+  virtual void OnDisplayAdded(const gfx::Display& /*new_display*/) OVERRIDE {}

[perkj_chrome, 2014/05/13 09:46:40]

style nit - name all arguments even if they are not used.

[Zachary Kuznia, 2014/05/13 13:54:29]

See:
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Functi...

+  virtual void OnDisplayRemoved(const gfx::Display& /*old_display*/) OVERRIDE {}
+
+  void AddObserverOnUIThread() {

[tommi (sloooow) - chröme, 2014/05/13 11:02:51]

nit: add a dcheck that we're indeed on the ui thread.

[Zachary Kuznia, 2014/05/13 13:54:29]

Done.

+    gfx::Screen* screen =
+        gfx::Screen::GetScreenByType(gfx::SCREEN_TYPE_ALTERNATE);
+    if (screen) {
+      screen->AddObserver(this);
+      SendDisplayRotation(screen->GetPrimaryDisplay());
+    }
+  }
+
+  void RemoveObserverOnUIThread() {
+    gfx::Screen* screen =

[tommi (sloooow) - chröme, 2014/05/13 11:02:51]

dcheck

[Zachary Kuznia, 2014/05/13 13:54:29]

Done.

+        gfx::Screen::GetScreenByType(gfx::SCREEN_TYPE_ALTERNATE);
+    if (screen)
+      screen->RemoveObserver(this);
+  }
+
+  void SendDisplayRotation(const gfx::Display& display) {
+    capture_thread_loop_->PostTask(

[perkj_chrome, 2014/05/13 09:46:40]

Can you add thread check here as well. 

[Zachary Kuznia, 2014/05/13 13:54:29]

Done.

+      FROM_HERE,

[perkj_chrome, 2014/05/13 09:46:40]

nit: intendation

[Zachary Kuznia, 2014/05/13 13:54:29]

Done.

+      base::Bind(&ScreenObserverDelegate::SendDisplayRotationOnCaptureThread,
+                 this, display));
+  }
+
+  void SendDisplayRotationOnCaptureThread(const gfx::Display& display) {
+    DCHECK(capture_thread_loop_ == base::MessageLoop::current());
+    capture_device_->SetDisplayRotation(display);
+  }
+

[perkj_chrome, 2014/05/13 09:46:40]

Can you add a threadchecker and verify that you are on the correct thread.

[Zachary Kuznia, 2014/05/13 13:54:29]

I don't think a threadchecker would be useful, because the constructor and
destructor are called on different threads.

+  VideoCaptureDeviceChromeOS* capture_device_;
+  base::MessageLoop* capture_thread_loop_;

[tommi (sloooow) - chröme, 2014/05/13 11:02:51]

if you use this variable on a thread other than the capture thread, then you
should be using MessageLoopProxy.  Maybe this is fine but it's not clear to me
from the code as is.

[Zachary Kuznia, 2014/05/13 13:54:29]

I actually used a MessageLoopProxy initially, but there is a presubmit error
that asserts:
"MessageLoopProxy should only be used for accessing the current loop."

[tommi (sloooow) - chröme, 2014/05/13 14:35:17]

Ah, I'm guessing this is the error you ran into:
https://code.google.com/p/chromium/codesearch#chromium/src/media/PRESUBMIT.py...

If so, then I think scoped_refptr<base::SingleThreadTaskRunner> is what you
want.  Sounds like you were going down the right path.  Where you call
MessageLoop::current() above, you should still call MessageLoopProxy::current().
 The only difference is the type of the variable that holds the pointer.

+  DISALLOW_IMPLICIT_CONSTRUCTORS(ScreenObserverDelegate);
+};
+
+
+VideoCaptureDeviceChromeOS::VideoCaptureDeviceChromeOS(const Name& device_name)
+    : VideoCaptureDeviceLinux(device_name),
+      screen_observer_delegate_(new ScreenObserverDelegate(this)) {
+}
+
+VideoCaptureDeviceChromeOS::~VideoCaptureDeviceChromeOS() {
+}
+
+void VideoCaptureDeviceChromeOS::SetDisplayRotation(
+    const gfx::Display& display) {
+  if (display.IsInternal())
+    SetRotation(display.rotation() * 90);
+}
+
+}  // namespace media