gecko-dev/dom/media/webrtc/MediaEngineSource.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef MediaEngineSource_h
#define MediaEngineSource_h

#include "MediaSegment.h"
#include "MediaTrackConstraints.h"
#include "mozilla/dom/MediaStreamTrackBinding.h"
#include "mozilla/media/MediaUtils.h"
#include "mozilla/RefPtr.h"
#include "mozilla/ThreadSafeWeakPtr.h"
#include "nsStringFwd.h"
#include "TrackID.h"

namespace mozilla {

namespace dom {
class Blob;
struct MediaTrackSettings;
} // namespace dom

namespace ipc {
class PrincipalInfo;
} // namespace ipc

class AllocationHandle;
class MediaEnginePhotoCallback;
class MediaEnginePrefs;
class SourceMediaStream;

/**
 * Callback interface for TakePhoto(). Either PhotoComplete() or PhotoError()
 * should be called.
 */
class MediaEnginePhotoCallback {
public:
  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MediaEnginePhotoCallback)

  // aBlob is the image captured by MediaEngineSource. It is
  // called on main thread.
  virtual nsresult PhotoComplete(already_AddRefed<dom::Blob> aBlob) = 0;

  // It is called on main thread. aRv is the error code.
  virtual nsresult PhotoError(nsresult aRv) = 0;

protected:
  virtual ~MediaEnginePhotoCallback() {}
};

/**
 * Lifecycle state of MediaEngineSource.
 */
enum MediaEngineSourceState {
  kAllocated, // Allocated, not yet started.
  kStarted, // Previously allocated or stopped, then started.
  kStopped, // Previously started, then stopped.
  kReleased // Not allocated.
};

/**
 * The pure interface of a MediaEngineSource.
 *
 * Most sources are helped by the defaults implemented in MediaEngineSource.
 */
class MediaEngineSourceInterface {
public:
  /**
   * Returns true if this source requires sharing to support multiple
   * allocations.
   *
   * If this returns true, the MediaEngine is expected to do subsequent
   * allocations on the first instance of this source.
   *
   * If this returns false, the MediaEngine is expected to instantiate one
   * source instance per allocation.
   *
   * Sharing means that the source gets multiple simultaneous calls to
   * Allocate(), Start(), Stop(), Deallocate(), etc. These are all keyed off
   * the AllocationHandle returned by Allocate() so the source can keep
   * allocations apart.
   *
   * A source typically requires sharing when the underlying hardware doesn't
   * allow multiple users, or when having multiple users would be inefficient.
   */
  virtual bool RequiresSharing() const = 0;

  /**
   * Return true if this is a fake source. I.e., if it is generating media
   * itself rather than being an interface to underlying hardware.
   */
  virtual bool IsFake() const = 0;

  /**
   * Gets the human readable name of this device.
   */
  virtual nsString GetName() const = 0;

  /**
   * Gets the UUID of this device.
   */
  virtual nsCString GetUUID() const = 0;

  /**
   * Get the enum describing the underlying type of MediaSource.
   */
  virtual dom::MediaSourceEnum GetMediaSource() const = 0;

  /**
   * Override w/true if source does end-run around cross origin restrictions.
   */
  virtual bool GetScary() const = 0;

  /**
   * Called by MediaEngine to allocate a handle to this source.
   *
   * If this is the first registered AllocationHandle, the underlying device
   * will be allocated.
   *
   * Note that the AllocationHandle may be nullptr at the discretion of the
   * MediaEngineSource implementation. Any user is to treat it as an opaque
   * object.
   */
  virtual nsresult Allocate(const dom::MediaTrackConstraints &aConstraints,
                            const MediaEnginePrefs &aPrefs,
                            const nsString& aDeviceId,
                            const mozilla::ipc::PrincipalInfo& aPrincipalInfo,
                            AllocationHandle** aOutHandle,
                            const char** aOutBadConstraint) = 0;

  /**
   * Called by MediaEngine when a SourceMediaStream and TrackID have been
   * provided for the given AllocationHandle to feed data to.
   *
   * This must be called before Start for the given AllocationHandle.
   */
  virtual nsresult SetTrack(const RefPtr<const AllocationHandle>& aHandle,
                            const RefPtr<SourceMediaStream>& aStream,
                            TrackID aTrackID,
                            const PrincipalHandle& aPrincipal) = 0;

  /**
   * Called by MediaEngine to start feeding data to the track associated with
   * the given AllocationHandle.
   *
   * If this is the first AllocationHandle to start, the underlying device
   * will be started.
   */
  virtual nsresult Start(const RefPtr<const AllocationHandle>& aHandle) = 0;

  /**
   * This brings focus to the selected source, e.g. to bring a captured window
   * to the front.
   *
   * We return one of the following:
   * NS_OK                    - Success.
   * NS_ERROR_NOT_AVAILABLE   - For backends where focusing does not make sense.
   * NS_ERROR_NOT_IMPLEMENTED - For backends where focusing makes sense, but
   *                            is not yet implemented.
   * NS_ERROR_FAILURE         - Failures reported from underlying code.
   */
  virtual nsresult FocusOnSelectedSource(const RefPtr<const AllocationHandle>& aHandle) = 0;

  /**
   * Applies new constraints to the capability selection for the underlying
   * device.
   *
   * Should the constraints lead to choosing a new capability while the device
   * is actively being captured, the device will restart using the new
   * capability.
   *
   * We return one of the following:
   * NS_OK                - Successful reconfigure.
   * NS_ERROR_INVALID_ARG - Couldn't find a capability fitting aConstraints.
   *                        See aBadConstraint for details.
   * NS_ERROR_UNEXPECTED  - Reconfiguring the underlying device failed
   *                        unexpectedly. This leaves the device in a stopped
   *                        state.
   */
  virtual nsresult Reconfigure(const RefPtr<AllocationHandle>& aHandle,
                               const dom::MediaTrackConstraints& aConstraints,
                               const MediaEnginePrefs& aPrefs,
                               const nsString& aDeviceId,
                               const char** aOutBadConstraint) = 0;

  /**
   * Called by MediaEngine to stop feeding data to the track associated with
   * the given AllocationHandle.
   *
   * If this was the last AllocationHandle that had been started,
   * the underlying device will be stopped.
   *
   * Double-stopping a given allocation handle is allowed and will return NS_OK.
   * This is necessary sometimes during shutdown.
   */
  virtual nsresult Stop(const RefPtr<const AllocationHandle>& aHandle) = 0;

  /**
   * Called by MediaEngine to deallocate a handle to this source.
   *
   * If this was the last registered AllocationHandle, the underlying device
   * will be deallocated.
   */
  virtual nsresult Deallocate(const RefPtr<const AllocationHandle>& aHandle) = 0;

  /**
   * Called by MediaEngine when it knows this MediaEngineSource won't be used
   * anymore. Use it to clean up anything that needs to be cleaned up.
   */
  virtual void Shutdown() = 0;

  /**
   * If implementation of MediaEngineSource supports TakePhoto(), the picture
   * should be returned via aCallback object. Otherwise, it returns NS_ERROR_NOT_IMPLEMENTED.
   */
  virtual nsresult TakePhoto(MediaEnginePhotoCallback* aCallback) = 0;

  /**
   * GetBestFitnessDistance returns the best distance the capture device can offer
   * as a whole, given an accumulated number of ConstraintSets.
   * Ideal values are considered in the first ConstraintSet only.
   * Plain values are treated as Ideal in the first ConstraintSet.
   * Plain values are treated as Exact in subsequent ConstraintSets.
   * Infinity = UINT32_MAX e.g. device cannot satisfy accumulated ConstraintSets.
   * A finite result may be used to calculate this device's ranking as a choice.
   */
  virtual uint32_t GetBestFitnessDistance(
      const nsTArray<const NormalizedConstraintSet*>& aConstraintSets,
      const nsString& aDeviceId) const = 0;

  /**
   * Returns the current settings of the underlying device.
   *
   * Note that this might not be the settings of the underlying hardware.
   * In case of a camera where we intervene and scale frames to avoid
   * leaking information from other documents than the current one,
   * GetSettings() will return the scaled resolution. I.e., the
   * device settings as seen by js.
   */
  virtual void GetSettings(dom::MediaTrackSettings& aOutSettings) const = 0;

  /**
   * Pulls data from the MediaEngineSource into the track.
   *
   * Driven by MediaStreamListener::NotifyPull.
   */
  virtual void Pull(const RefPtr<const AllocationHandle>& aHandle,
                    const RefPtr<SourceMediaStream>& aStream,
                    TrackID aTrackID,
                    StreamTime aDesiredTime,
                    const PrincipalHandle& aPrincipalHandle) = 0;
};

/**
 * Abstract base class for MediaEngineSources.
 *
 * Implements defaults for some common MediaEngineSourceInterface methods below.
 * Also implements RefPtr support and an owning-thread model for thread safety
 * checks in subclasses.
 */
class MediaEngineSource : public MediaEngineSourceInterface {
public:

  // code inside webrtc.org assumes these sizes; don't use anything smaller
  // without verifying it's ok
  static const unsigned int kMaxDeviceNameLength = 128;
  static const unsigned int kMaxUniqueIdLength = 256;

  /**
   * Returns true if the given source type is for video, false otherwise.
   * Only call with real types.
   */
  static bool IsVideo(dom::MediaSourceEnum aSource);

  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MediaEngineSource)
  NS_DECL_OWNINGTHREAD

  void AssertIsOnOwningThread() const
  {
    NS_ASSERT_OWNINGTHREAD(MediaEngineSource);
  }

  // No sharing required by default.
  bool RequiresSharing() const override;

  // Not fake by default.
  bool IsFake() const override;

  // Not scary by default.
  bool GetScary() const override;

  // Returns NS_ERROR_NOT_AVAILABLE by default.
  nsresult FocusOnSelectedSource(const RefPtr<const AllocationHandle>& aHandle) override;

  // Shutdown does nothing by default.
  void Shutdown() override;

  // TakePhoto returns NS_ERROR_NOT_IMPLEMENTED by default,
  // to tell the caller to fallback to other methods.
  nsresult TakePhoto(MediaEnginePhotoCallback* aCallback) override;

  // Makes aOutSettings empty by default.
  void GetSettings(dom::MediaTrackSettings& aOutSettings) const override;

protected:
  virtual ~MediaEngineSource();
};

} // namespace mozilla

#endif /* MediaEngineSource_h */