image/IDecodingTask.cpp
author Andrew Osmond <aosmond@mozilla.com>
Thu, 01 Nov 2018 16:36:16 -0400
changeset 444021 5223058ac4fffd00aad34eeb29998c3264b250e8
parent 369669 8941aa986abc5d3ba40d8f48d840da5bbf840df1
child 448947 6f3709b3878117466168c40affa7bca0b60cf75b
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/. */

#include "IDecodingTask.h"

#include "gfxPrefs.h"
#include "nsThreadUtils.h"

#include "Decoder.h"
#include "DecodePool.h"
#include "RasterImage.h"
#include "SurfaceCache.h"

#include "mozilla/SystemGroup.h"

namespace mozilla {

using gfx::IntRect;

namespace image {

///////////////////////////////////////////////////////////////////////////////
// Helpers for sending notifications to the image associated with a decoder.
///////////////////////////////////////////////////////////////////////////////

void
IDecodingTask::EnsureHasEventTarget(NotNull<RasterImage*> aImage)
{
  if (!mEventTarget) {
    // We determine the event target as late as possible, at the first dispatch
    // time, because the observers bound to an imgRequest will affect it.
    // We cache it rather than query for the event target each time because the
    // event target can change. We don't want to risk events being executed in
    // a different order than they are dispatched, which can happen if we
    // selected scheduler groups which have no ordering guarantees relative to
    // each other (e.g. it moves from scheduler group A for doc group DA to
    // scheduler group B for doc group DB due to changing observers -- if we
    // dispatched the first event on A, and the second on B, we don't know which
    // will execute first.)
    RefPtr<ProgressTracker> tracker = aImage->GetProgressTracker();
    if (tracker) {
      mEventTarget = tracker->GetEventTarget();
    } else {
      mEventTarget = SystemGroup::EventTargetFor(TaskCategory::Other);
    }
  }
}

bool
IDecodingTask::IsOnEventTarget() const
{
  // This is essentially equivalent to NS_IsOnMainThread() because all of the
  // event targets are for the main thread (although perhaps with a different
  // label / scheduler group). The observers in ProgressTracker may have
  // different event targets from this, so this is just a best effort guess.
  bool current = false;
  mEventTarget->IsOnCurrentThread(&current);
  return current;
}

void
IDecodingTask::NotifyProgress(NotNull<RasterImage*> aImage,
                              NotNull<Decoder*> aDecoder)
{
  MOZ_ASSERT(aDecoder->HasProgress() && !aDecoder->IsMetadataDecode());
  EnsureHasEventTarget(aImage);

  // Capture the decoder's state. If we need to notify asynchronously, it's
  // important that we don't wait until the lambda actually runs to capture the
  // state that we're going to notify. That would both introduce data races on
  // the decoder's state and cause inconsistencies between the NotifyProgress()
  // calls we make off-main-thread and the notifications that RasterImage
  // actually receives, which would cause bugs.
  Progress progress = aDecoder->TakeProgress();
  IntRect invalidRect = aDecoder->TakeInvalidRect();
  Maybe<uint32_t> frameCount = aDecoder->TakeCompleteFrameCount();
  DecoderFlags decoderFlags = aDecoder->GetDecoderFlags();
  SurfaceFlags surfaceFlags = aDecoder->GetSurfaceFlags();

  // Synchronously notify if we can.
  if (IsOnEventTarget() && !(decoderFlags & DecoderFlags::ASYNC_NOTIFY)) {
    aImage->NotifyProgress(progress, invalidRect, frameCount,
                           decoderFlags, surfaceFlags);
    return;
  }

  // We're forced to notify asynchronously.
  NotNull<RefPtr<RasterImage>> image = aImage;
  mEventTarget->Dispatch(NS_NewRunnableFunction(
                           "IDecodingTask::NotifyProgress",
                           [=]() -> void {
    image->NotifyProgress(progress, invalidRect, frameCount,
                          decoderFlags, surfaceFlags);
  }), NS_DISPATCH_NORMAL);
}

void
IDecodingTask::NotifyDecodeComplete(NotNull<RasterImage*> aImage,
                                    NotNull<Decoder*> aDecoder)
{
  MOZ_ASSERT(aDecoder->HasError() || !aDecoder->InFrame(),
             "Decode complete in the middle of a frame?");
  EnsureHasEventTarget(aImage);

  // Capture the decoder's state.
  DecoderFinalStatus finalStatus = aDecoder->FinalStatus();
  ImageMetadata metadata = aDecoder->GetImageMetadata();
  DecoderTelemetry telemetry = aDecoder->Telemetry();
  Progress progress = aDecoder->TakeProgress();
  IntRect invalidRect = aDecoder->TakeInvalidRect();
  Maybe<uint32_t> frameCount = aDecoder->TakeCompleteFrameCount();
  DecoderFlags decoderFlags = aDecoder->GetDecoderFlags();
  SurfaceFlags surfaceFlags = aDecoder->GetSurfaceFlags();

  // Synchronously notify if we can.
  if (IsOnEventTarget() && !(decoderFlags & DecoderFlags::ASYNC_NOTIFY)) {
    aImage->NotifyDecodeComplete(finalStatus, metadata, telemetry, progress,
                                 invalidRect, frameCount, decoderFlags,
                                 surfaceFlags);
    return;
  }

  // We're forced to notify asynchronously.
  NotNull<RefPtr<RasterImage>> image = aImage;
  mEventTarget->Dispatch(NS_NewRunnableFunction(
                           "IDecodingTask::NotifyDecodeComplete",
                           [=]() -> void {
    image->NotifyDecodeComplete(finalStatus, metadata, telemetry, progress,
                                invalidRect, frameCount, decoderFlags,
                                surfaceFlags);
  }), NS_DISPATCH_NORMAL);
}


///////////////////////////////////////////////////////////////////////////////
// IDecodingTask implementation.
///////////////////////////////////////////////////////////////////////////////

void
IDecodingTask::Resume()
{
  DecodePool::Singleton()->AsyncRun(this);
}


///////////////////////////////////////////////////////////////////////////////
// MetadataDecodingTask implementation.
///////////////////////////////////////////////////////////////////////////////

MetadataDecodingTask::MetadataDecodingTask(NotNull<Decoder*> aDecoder)
  : mMutex("mozilla::image::MetadataDecodingTask")
  , mDecoder(aDecoder)
{
  MOZ_ASSERT(mDecoder->IsMetadataDecode(),
             "Use DecodingTask for non-metadata decodes");
}

void
MetadataDecodingTask::Run()
{
  MutexAutoLock lock(mMutex);

  LexerResult result = mDecoder->Decode(WrapNotNull(this));

  if (result.is<TerminalState>()) {
    NotifyDecodeComplete(mDecoder->GetImage(), mDecoder);
    return;  // We're done.
  }

  if (result == LexerResult(Yield::NEED_MORE_DATA)) {
    // We can't make any more progress right now. We also don't want to report
    // any progress, because it's important that metadata decode results are
    // delivered atomically. The decoder itself will ensure that we get
    // reenqueued when more data is available; just return for now.
    return;
  }

  MOZ_ASSERT_UNREACHABLE("Metadata decode yielded for an unexpected reason");
}


///////////////////////////////////////////////////////////////////////////////
// AnonymousDecodingTask implementation.
///////////////////////////////////////////////////////////////////////////////

AnonymousDecodingTask::AnonymousDecodingTask(NotNull<Decoder*> aDecoder,
                                             bool aResumable)
  : mDecoder(aDecoder)
  , mResumable(aResumable)
{ }

void
AnonymousDecodingTask::Run()
{
  while (true) {
    LexerResult result = mDecoder->Decode(WrapNotNull(this));

    if (result.is<TerminalState>()) {
      return;  // We're done.
    }

    if (result == LexerResult(Yield::NEED_MORE_DATA)) {
      // We can't make any more progress right now. Let the caller decide how to
      // handle it.
      return;
    }

    // Right now we don't do anything special for other kinds of yields, so just
    // keep working.
    MOZ_ASSERT(result.is<Yield>());
  }
}

void
AnonymousDecodingTask::Resume()
{
  // Anonymous decoders normally get all their data at once. We have tests
  // where they don't; typically in these situations, the test re-runs them
  // manually. However some tests want to verify Resume works, so they will
  // explicitly request this behaviour.
  if (mResumable) {
    RefPtr<AnonymousDecodingTask> self(this);
    NS_DispatchToMainThread(NS_NewRunnableFunction(
      "image::AnonymousDecodingTask::Resume",
      [self]() -> void { self->Run(); }));
  }
}

} // namespace image
} // namespace mozilla