image/IDecodingTask.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 /**
   7  * An interface for tasks which can execute on the ImageLib DecodePool, and
   8  * various implementations.
   9  */
  10
  11 #ifndef mozilla_image_IDecodingTask_h
  12 #define mozilla_image_IDecodingTask_h
  13
  14 #include "imgFrame.h"
  15 #include "mozilla/NotNull.h"
  16 #include "mozilla/RefPtr.h"
  17 #include "nsIEventTarget.h"
  18 #include "SourceBuffer.h"
  19
  20 namespace mozilla {
  21 namespace image {
  22
  23 class Decoder;
  24 class RasterImage;
  25
  26 /// A priority hint that DecodePool can use when scheduling an IDecodingTask.
  27 enum class TaskPriority : uint8_t { eLow, eHigh };
  28
  29 /**
  30  * An interface for tasks which can execute on the ImageLib DecodePool.
  31  */
  32 class IDecodingTask : public IResumable {
  33  public:
  34   /// Run the task.
  35   virtual void Run() = 0;
  36
  37   /// @return true if, given the option, this task prefers to run synchronously.
  38   virtual bool ShouldPreferSyncRun() const = 0;
  39
  40   /// @return a priority hint that DecodePool can use when scheduling this task.
  41   virtual TaskPriority Priority() const = 0;
  42
  43   /// A default implementation of IResumable which resubmits the task to the
  44   /// DecodePool. Subclasses can override this if they need different behavior.
  45   void Resume() override;
  46
  47  protected:
  48   virtual ~IDecodingTask() {}
  49
  50   /// Notify @aImage of @aDecoder's progress.
  51   void NotifyProgress(NotNull<RasterImage*> aImage, NotNull<Decoder*> aDecoder);
  52
  53   /// Notify @aImage that @aDecoder has finished.
  54   void NotifyDecodeComplete(NotNull<RasterImage*> aImage,
  55                             NotNull<Decoder*> aDecoder);
  56 };
  57
  58 /**
  59  * An IDecodingTask implementation for metadata decodes of images.
  60  */
  61 class MetadataDecodingTask final : public IDecodingTask {
  62  public:
  63   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MetadataDecodingTask, override)
  64
  65   explicit MetadataDecodingTask(NotNull<Decoder*> aDecoder);
  66
  67   void Run() override;
  68
  69   // Metadata decodes are very fast (since they only need to examine an image's
  70   // header) so there's no reason to refuse to run them synchronously if the
  71   // caller will allow us to.
  72   bool ShouldPreferSyncRun() const override { return true; }
  73
  74   // Metadata decodes run at the highest priority because they block layout and
  75   // page load.
  76   TaskPriority Priority() const override { return TaskPriority::eHigh; }
  77
  78  private:
  79   virtual ~MetadataDecodingTask() {}
  80
  81   /// Mutex protecting access to mDecoder.
  82   Mutex mMutex MOZ_UNANNOTATED;
  83
  84   NotNull<RefPtr<Decoder>> mDecoder;
  85 };
  86
  87 /**
  88  * An IDecodingTask implementation for anonymous decoders - that is, decoders
  89  * with no associated Image object.
  90  */
  91 class AnonymousDecodingTask final : public IDecodingTask {
  92  public:
  93   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(AnonymousDecodingTask, override)
  94
  95   explicit AnonymousDecodingTask(NotNull<Decoder*> aDecoder, bool aResumable);
  96
  97   void Run() override;
  98
  99   bool ShouldPreferSyncRun() const override { return true; }
 100   TaskPriority Priority() const override { return TaskPriority::eLow; }
 101
 102   void Resume() override;
 103
 104  private:
 105   virtual ~AnonymousDecodingTask() {}
 106
 107   NotNull<RefPtr<Decoder>> mDecoder;
 108   bool mResumable;
 109 };
 110
 111 }  // namespace image
 112 }  // namespace mozilla
 113
 114 #endif  // mozilla_image_IDecodingTask_h