gecko-dev/image/IDecodingTask.h

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/* -*- 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 "mozilla/NotNull.h"
#include "mozilla/RefPtr.h"
#include "SourceBuffer.h"
namespace mozilla {
namespace image {
class Decoder;
/// 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;
/// @return a non-null weak pointer to the Decoder associated with this task.
virtual NotNull<Decoder*> GetDecoder() const = 0;
// Notify the Image associated with a Decoder of its progress, sending a
// runnable to the main thread if necessary.
// XXX(seth): This is a hack that will be removed soon.
static void NotifyProgress(NotNull<Decoder*> aDecoder);
protected:
virtual ~IDecodingTask() { }
};
/**
* An IDecodingTask implementation for full decodes of images.
*/
class DecodingTask final : public IDecodingTask
{
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DecodingTask, override)
explicit DecodingTask(NotNull<Decoder*> aDecoder);
void Run() override;
bool ShouldPreferSyncRun() const override;
// Full decodes are low priority compared to metadata decodes because they
// don't block layout or page load.
TaskPriority Priority() const override { return TaskPriority::eLow; }
NotNull<Decoder*> GetDecoder() const override { return mDecoder; }
private:
virtual ~DecodingTask() { }
NotNull<RefPtr<Decoder>> mDecoder;
};
/**
* 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; }
NotNull<Decoder*> GetDecoder() const override { return mDecoder; }
private:
virtual ~MetadataDecodingTask() { }
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);
void Run() override;
bool ShouldPreferSyncRun() const override { return true; }
TaskPriority Priority() const override { return TaskPriority::eLow; }
// Anonymous decoders normally get all their data at once. We have tests where
// they don't; in these situations, the test re-runs them manually. So no
// matter what, we don't want to resume by posting a task to the DecodePool.
void Resume() override { }
NotNull<Decoder*> GetDecoder() const override { return mDecoder; }
private:
virtual ~AnonymousDecodingTask() { }
NotNull<RefPtr<Decoder>> mDecoder;
};
} // namespace image
} // namespace mozilla
#endif // mozilla_image_IDecodingTask_h