Reland: Image Capture Linux/CrOs: wire some capabilities set/get

media/capture/video/linux/v4l2_capture_delegate.h

 // 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.
 
 #ifndef MEDIA_CAPTURE_VIDEO_LINUX_V4L2_CAPTURE_DELEGATE_H_
 #define MEDIA_CAPTURE_VIDEO_LINUX_V4L2_CAPTURE_DELEGATE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 12 matching lines @@
 namespace tracked_objects {
 class Location;
 }  // namespace tracked_objects
 
 namespace media {
 
 // Class doing the actual Linux capture using V4L2 API. V4L2 SPLANE/MPLANE
 // capture specifics are implemented in derived classes. Created and destroyed
 // on the owner's thread, otherwise living and operating on |v4l2_task_runner_|.
 // TODO(mcasas): Make this class a non-ref-counted.
 class V4L2CaptureDelegate final

[chfremer, 2016/09/23 21:18:29]

Question/suggestion unrelated to this CL:
Why is this not an implementation of media::VideoCaptureDevice?
It seems the class VideoCaptureDeviceLinux forward all calls to an instance of
this class on a different thread. If V4L2CaptureDelegate would implement
media::VideoCaptureDevice and VideoCaptureDeviceLinux would depend on the
interface instead of the concrete V4L2CaptureDelegate, then this would be the
decorator pattern.

This would help readers understand the role and contract of V4L2CaptureDelegate.

[mcasas, 2016/09/23 22:10:57]

History. It used to be inside VideoCaptureDeviceLinux,
but then 2 V4L2 implementations came around, one for
single and one for multiplanar versions. The latter
was removed, and things never consolidated.

     : public base::RefCountedThreadSafe<V4L2CaptureDelegate> {
  public:
   // Retrieves the #planes for a given |fourcc|, or 0 if unknown.
   static size_t GetNumPlanesForFourCc(uint32_t fourcc);
   // Returns the Chrome pixel format for |v4l2_fourcc| or PIXEL_FORMAT_UNKNOWN.
   static VideoPixelFormat V4l2FourCcToChromiumPixelFormat(
       uint32_t v4l2_fourcc);
 
   // Composes a list of usable and supported pixel formats, in order of
   // preference, with MJPEG prioritised depending on |prefer_mjpeg|.
   static std::list<uint32_t> GetListOfUsableFourCcs(bool prefer_mjpeg);
 
   V4L2CaptureDelegate(
       const VideoCaptureDeviceDescriptor& device_descriptor,
       const scoped_refptr<base::SingleThreadTaskRunner>& v4l2_task_runner,
       int power_line_frequency);
 
   // Forward-to versions of VideoCaptureDevice virtual methods.
   void AllocateAndStart(int width,
                         int height,
                         float frame_rate,
                         std::unique_ptr<VideoCaptureDevice::Client> client);
   void StopAndDeAllocate();
 
   void TakePhoto(VideoCaptureDevice::TakePhotoCallback callback);
 
+  void GetPhotoCapabilities(
+      VideoCaptureDevice::GetPhotoCapabilitiesCallback callback);
+  void SetPhotoOptions(mojom::PhotoSettingsPtr settings,

[chfremer, 2016/09/23 21:18:29]

nit: photo options vs. photo settings, could be made consistent

[mcasas, 2016/09/23 22:10:57]

They follow the idl names, which in turn come
from the JS spec. [1], [2].

You can file a spec-bug! :-)
https://github.com/w3c/mediacapture-image/issues/new

[1]
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/modules/imagec...
[2]
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/modules/imagec...

+                       VideoCaptureDevice::SetPhotoOptionsCallback callback);
+
   void SetRotation(int rotation);
 
  private:
   friend class base::RefCountedThreadSafe<V4L2CaptureDelegate>;
   ~V4L2CaptureDelegate();
 
   class BufferTracker;
 
   // VIDIOC_QUERYBUFs a buffer from V4L2, creates a BufferTracker for it and
   // enqueues it (VIDIOC_QBUF) back into V4L2.
@@ skipping 24 matching lines @@
 
   // Clockwise rotation in degrees. This value should be 0, 90, 180, or 270.
   int rotation_;
 
   DISALLOW_COPY_AND_ASSIGN(V4L2CaptureDelegate);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CAPTURE_VIDEO_LINUX_V4L2_CAPTURE_DELEGATE_H_