1 files changed, 221 insertions, 0 deletions
diff --git a/image/IDecodingTask.cpp b/image/IDecodingTask.cpp
new file mode 100644
index 0000000000..1816c9056b
--- /dev/null
+++ b/image/IDecodingTask.cpp
@@ -0,0 +1,221 @@
+/* -*- 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 "nsThreadUtils.h"
+#include "mozilla/AppShutdown.h"
+
+#include "Decoder.h"
+#include "DecodePool.h"
+#include "RasterImage.h"
+#include "SurfaceCache.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 = GetMainThreadSerialEventTarget();
+    }
+  }
+}
+
+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();
+  OrientedIntRect 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;
+  }
+
+  // Don't try to dispatch after shutdown, we'll just leak the runnable.
+  if (NS_WARN_IF(
+          AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdownThreads))) {
+    return;
+  }
+
+  // We're forced to notify asynchronously.
+  NotNull<RefPtr<RasterImage>> image = aImage;
+  mEventTarget->Dispatch(CreateRenderBlockingRunnable(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();
+  OrientedIntRect 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;
+  }
+
+  // Don't try to dispatch after shutdown, we'll just leak the runnable.
+  if (NS_WARN_IF(
+          AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdownThreads))) {
+    return;
+  }
+
+  // We're forced to notify asynchronously.
+  NotNull<RefPtr<RasterImage>> image = aImage;
+  mEventTarget->Dispatch(CreateRenderBlockingRunnable(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