image/IDecodingTask.h
author Andrew Osmond <aosmond@mozilla.com>
Thu, 01 Nov 2018 16:36:16 -0400
changeset 444045 5223058ac4fffd00aad34eeb29998c3264b250e8
parent 391975 7159964287fe161b0dda9cdfa59d74bc7bead348
child 448185 98430e6d541b8e5ffd0492d84afd5c031eb79905
permissions -rw-r--r--
Bug 1503935 - Fix some WebP decoder implementation bugs. r=tnikkel First we did not handle the SourceBufferIterator::WAITING state which can happen when we get woken up but there is no data to read from the SourceBufferIterator. StreamingLexer handled this properly by yielding with NEED_MORE_DATA, and properly scheduling the decoder to resume. This patch does the same in the WebP decoder. Second nsWebPDecoder::GetType was not implemented. This meant it would return DecoderType::UNKNOWN, and would fail to recreate the decoder if we are discarding frames and need to restart from the beginning. In addition to implementing that method, this patch also corrects an assert in DecoderFactory::CloneAnimationDecoder which failed to check for WebP as a supported animated decoder. This patch also modestly improves the logging output and library method checks. Differential Revision: https://phabricator.services.mozilla.com/D10624

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

/**
 * An interface for tasks which can execute on the ImageLib DecodePool, and
 * various implementations.
 */

#ifndef mozilla_image_IDecodingTask_h
#define mozilla_image_IDecodingTask_h

#include "imgFrame.h"
#include "mozilla/NotNull.h"
#include "mozilla/RefPtr.h"
#include "nsIEventTarget.h"
#include "SourceBuffer.h"

namespace mozilla {
namespace image {

class Decoder;
class RasterImage;

/// A priority hint that DecodePool can use when scheduling an IDecodingTask.
enum class TaskPriority : uint8_t
{
  eLow,
  eHigh
};

/**
 * An interface for tasks which can execute on the ImageLib DecodePool.
 */
class IDecodingTask : public IResumable
{
public:
  /// Run the task.
  virtual void Run() = 0;

  /// @return true if, given the option, this task prefers to run synchronously.
  virtual bool ShouldPreferSyncRun() const = 0;

  /// @return a priority hint that DecodePool can use when scheduling this task.
  virtual TaskPriority Priority() const = 0;

  /// A default implementation of IResumable which resubmits the task to the
  /// DecodePool. Subclasses can override this if they need different behavior.
  void Resume() override;

protected:
  virtual ~IDecodingTask() { }

  /// Notify @aImage of @aDecoder's progress.
  void NotifyProgress(NotNull<RasterImage*> aImage,
                      NotNull<Decoder*> aDecoder);

  /// Notify @aImage that @aDecoder has finished.
  void NotifyDecodeComplete(NotNull<RasterImage*> aImage,
                            NotNull<Decoder*> aDecoder);

private:
  void EnsureHasEventTarget(NotNull<RasterImage*> aImage);

  bool IsOnEventTarget() const;

  nsCOMPtr<nsIEventTarget> mEventTarget;
};


/**
 * An IDecodingTask implementation for metadata decodes of images.
 */
class MetadataDecodingTask final : public IDecodingTask
{
public:
  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MetadataDecodingTask, override)

  explicit MetadataDecodingTask(NotNull<Decoder*> aDecoder);

  void Run() override;

  // Metadata decodes are very fast (since they only need to examine an image's
  // header) so there's no reason to refuse to run them synchronously if the
  // caller will allow us to.
  bool ShouldPreferSyncRun() const override { return true; }

  // Metadata decodes run at the highest priority because they block layout and
  // page load.
  TaskPriority Priority() const override { return TaskPriority::eHigh; }

private:
  virtual ~MetadataDecodingTask() { }

  /// Mutex protecting access to mDecoder.
  Mutex mMutex;

  NotNull<RefPtr<Decoder>> mDecoder;
};


/**
 * An IDecodingTask implementation for anonymous decoders - that is, decoders
 * with no associated Image object.
 */
class AnonymousDecodingTask final : public IDecodingTask
{
public:
  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(AnonymousDecodingTask, override)

  explicit AnonymousDecodingTask(NotNull<Decoder*> aDecoder,
                                 bool aResumable);

  void Run() override;

  bool ShouldPreferSyncRun() const override { return true; }
  TaskPriority Priority() const override { return TaskPriority::eLow; }

  void Resume() override;

private:
  virtual ~AnonymousDecodingTask() { }

  NotNull<RefPtr<Decoder>> mDecoder;
  bool mResumable;
};

} // namespace image
} // namespace mozilla

#endif // mozilla_image_IDecodingTask_h