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  private:
  58   void EnsureHasEventTarget(NotNull<RasterImage*> aImage);
  59
  60   bool IsOnEventTarget() const;
  61
  62   nsCOMPtr<nsIEventTarget> mEventTarget;
  63 };
  64
  65 /**
  66  * An IDecodingTask implementation for metadata decodes of images.
  67  */
  68 class MetadataDecodingTask final : public IDecodingTask {
  69  public:
  70   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(MetadataDecodingTask, override)
  71
  72   explicit MetadataDecodingTask(NotNull<Decoder*> aDecoder);
  73
  74   void Run() override;
  75
  76   // Metadata decodes are very fast (since they only need to examine an image's
  77   // header) so there's no reason to refuse to run them synchronously if the
  78   // caller will allow us to.
  79   bool ShouldPreferSyncRun() const override { return true; }
  80
  81   // Metadata decodes run at the highest priority because they block layout and
  82   // page load.
  83   TaskPriority Priority() const override { return TaskPriority::eHigh; }
  84
  85  private:
  86   virtual ~MetadataDecodingTask() {}
  87
  88   /// Mutex protecting access to mDecoder.
  89   Mutex mMutex;
  90
  91   NotNull<RefPtr<Decoder>> mDecoder;
  92 };
  93
  94 /**
  95  * An IDecodingTask implementation for anonymous decoders - that is, decoders
  96  * with no associated Image object.
  97  */
  98 class AnonymousDecodingTask final : public IDecodingTask {
  99  public:
 100   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(AnonymousDecodingTask, override)
 101
 102   explicit AnonymousDecodingTask(NotNull<Decoder*> aDecoder, bool aResumable);
 103
 104   void Run() override;
 105
 106   bool ShouldPreferSyncRun() const override { return true; }
 107   TaskPriority Priority() const override { return TaskPriority::eLow; }
 108
 109   void Resume() override;
 110
 111  private:
 112   virtual ~AnonymousDecodingTask() {}
 113
 114   NotNull<RefPtr<Decoder>> mDecoder;
 115   bool mResumable;
 116 };
 117
 118 }  // namespace image
 119 }  // namespace mozilla
 120
 121 #endif  // mozilla_image_IDecodingTask_h