image/DecodedSurfaceProvider.cpp

   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 #include "DecodedSurfaceProvider.h"
   7
   8 #include "mozilla/StaticPrefs_image.h"
   9 #include "nsProxyRelease.h"
  10
  11 #include "Decoder.h"
  12
  13 using namespace mozilla::gfx;
  14
  15 namespace mozilla {
  16 namespace image {
  17
  18 DecodedSurfaceProvider::DecodedSurfaceProvider(NotNull<RasterImage*> aImage,
  19                                                const SurfaceKey& aSurfaceKey,
  20                                                NotNull<Decoder*> aDecoder)
  21     : ISurfaceProvider(ImageKey(aImage.get()), aSurfaceKey,
  22                        AvailabilityState::StartAsPlaceholder()),
  23       mImage(aImage.get()),
  24       mMutex("mozilla::image::DecodedSurfaceProvider"),
  25       mDecoder(aDecoder.get()) {
  26   MOZ_ASSERT(!mDecoder->IsMetadataDecode(),
  27              "Use MetadataDecodingTask for metadata decodes");
  28   MOZ_ASSERT(mDecoder->IsFirstFrameDecode(),
  29              "Use AnimationSurfaceProvider for animation decodes");
  30 }
  31
  32 DecodedSurfaceProvider::~DecodedSurfaceProvider() { DropImageReference(); }
  33
  34 void DecodedSurfaceProvider::DropImageReference() {
  35   if (!mImage) {
  36     return;  // Nothing to do.
  37   }
  38
  39   // RasterImage objects need to be destroyed on the main thread. We also need
  40   // to destroy them asynchronously, because if our surface cache entry is
  41   // destroyed and we were the only thing keeping |mImage| alive, RasterImage's
  42   // destructor may call into the surface cache while whatever code caused us to
  43   // get evicted is holding the surface cache lock, causing deadlock.
  44   RefPtr<RasterImage> image = mImage;
  45   mImage = nullptr;
  46   NS_ReleaseOnMainThread(image.forget(), /* aAlwaysProxy = */ true);
  47 }
  48
  49 DrawableFrameRef DecodedSurfaceProvider::DrawableRef(size_t aFrame) {
  50   MOZ_ASSERT(aFrame == 0,
  51              "Requesting an animation frame from a DecodedSurfaceProvider?");
  52
  53   // We depend on SurfaceCache::SurfaceAvailable() to provide synchronization
  54   // for methods that touch |mSurface|; after SurfaceAvailable() is called,
  55   // |mSurface| should be non-null and shouldn't be mutated further until we get
  56   // destroyed. That means that the assertions below are very important; we'll
  57   // end up with data races if these assumptions are violated.
  58   if (Availability().IsPlaceholder()) {
  59     MOZ_ASSERT_UNREACHABLE("Calling DrawableRef() on a placeholder");
  60     return DrawableFrameRef();
  61   }
  62
  63   if (!mSurface) {
  64     MOZ_ASSERT_UNREACHABLE("Calling DrawableRef() when we have no surface");
  65     return DrawableFrameRef();
  66   }
  67
  68   return mSurface->DrawableRef();
  69 }
  70
  71 bool DecodedSurfaceProvider::IsFinished() const {
  72   // See DrawableRef() for commentary on these assertions.
  73   if (Availability().IsPlaceholder()) {
  74     MOZ_ASSERT_UNREACHABLE("Calling IsFinished() on a placeholder");
  75     return false;
  76   }
  77
  78   if (!mSurface) {
  79     MOZ_ASSERT_UNREACHABLE("Calling IsFinished() when we have no surface");
  80     return false;
  81   }
  82
  83   return mSurface->IsFinished();
  84 }
  85
  86 void DecodedSurfaceProvider::SetLocked(bool aLocked) {
  87   // See DrawableRef() for commentary on these assertions.
  88   if (Availability().IsPlaceholder()) {
  89     MOZ_ASSERT_UNREACHABLE("Calling SetLocked() on a placeholder");
  90     return;
  91   }
  92
  93   if (!mSurface) {
  94     MOZ_ASSERT_UNREACHABLE("Calling SetLocked() when we have no surface");
  95     return;
  96   }
  97
  98   if (aLocked == IsLocked()) {
  99     return;  // Nothing to do.
 100   }
 101
 102   // If we're locked, hold a DrawableFrameRef to |mSurface|, which will keep any
 103   // volatile buffer it owns in memory.
 104   mLockRef = aLocked ? mSurface->DrawableRef() : DrawableFrameRef();
 105 }
 106
 107 size_t DecodedSurfaceProvider::LogicalSizeInBytes() const {
 108   // Single frame images are always 32bpp.
 109   IntSize size = GetSurfaceKey().Size();
 110   return size_t(size.width) * size_t(size.height) * sizeof(uint32_t);
 111 }
 112
 113 void DecodedSurfaceProvider::Run() {
 114   MutexAutoLock lock(mMutex);
 115
 116   if (!mDecoder || !mImage) {
 117     MOZ_ASSERT_UNREACHABLE("Running after decoding finished?");
 118     return;
 119   }
 120
 121   // Run the decoder.
 122   LexerResult result = mDecoder->Decode(WrapNotNull(this));
 123
 124   // If there's a new surface available, announce it to the surface cache.
 125   CheckForNewSurface();
 126
 127   if (result.is<TerminalState>()) {
 128     FinishDecoding();
 129     return;  // We're done.
 130   }
 131
 132   // Notify for the progress we've made so far.
 133   if (mDecoder->HasProgress()) {
 134     NotifyProgress(WrapNotNull(mImage), WrapNotNull(mDecoder));
 135   }
 136
 137   MOZ_ASSERT(result.is<Yield>());
 138
 139   if (result == LexerResult(Yield::NEED_MORE_DATA)) {
 140     // We can't make any more progress right now. The decoder itself will ensure
 141     // that we get reenqueued when more data is available; just return for now.
 142     return;
 143   }
 144
 145   // Single-frame images shouldn't yield for any reason except NEED_MORE_DATA.
 146   MOZ_ASSERT_UNREACHABLE("Unexpected yield for single-frame image");
 147   mDecoder->TerminateFailure();
 148   FinishDecoding();
 149 }
 150
 151 void DecodedSurfaceProvider::CheckForNewSurface() {
 152   mMutex.AssertCurrentThreadOwns();
 153   MOZ_ASSERT(mDecoder);
 154
 155   if (mSurface) {
 156     // Single-frame images should produce no more than one surface, so if we
 157     // have one, it should be the same one the decoder is working on.
 158     MOZ_ASSERT(mSurface.get() == mDecoder->GetCurrentFrameRef().get(),
 159                "DecodedSurfaceProvider and Decoder have different surfaces?");
 160     return;
 161   }
 162
 163   // We don't have a surface yet; try to get one from the decoder.
 164   mSurface = mDecoder->GetCurrentFrameRef().get();
 165   if (!mSurface) {
 166     return;  // No surface yet.
 167   }
 168
 169   // We just got a surface for the first time; let the surface cache know.
 170   MOZ_ASSERT(mImage);
 171   SurfaceCache::SurfaceAvailable(WrapNotNull(this));
 172 }
 173
 174 void DecodedSurfaceProvider::FinishDecoding() {
 175   mMutex.AssertCurrentThreadOwns();
 176   MOZ_ASSERT(mImage);
 177   MOZ_ASSERT(mDecoder);
 178
 179   // Send notifications.
 180   NotifyDecodeComplete(WrapNotNull(mImage), WrapNotNull(mDecoder));
 181
 182   // If we have a new and complete surface, we can try to prune similarly sized
 183   // surfaces if the cache supports it.
 184   if (mSurface && mSurface->IsFinished()) {
 185     SurfaceCache::PruneImage(ImageKey(mImage));
 186   }
 187
 188   // Destroy our decoder; we don't need it anymore. (And if we don't destroy it,
 189   // our surface can never be optimized, because the decoder has a
 190   // RawAccessFrameRef to it.)
 191   mDecoder = nullptr;
 192
 193   // We don't need a reference to our image anymore, either, and we don't want
 194   // one. We may be stored in the surface cache for a long time after decoding
 195   // finishes. If we don't drop our reference to the image, we'll end up
 196   // keeping it alive as long as we remain in the surface cache, which could
 197   // greatly extend the image's lifetime - in fact, if the image isn't
 198   // discardable, it'd result in a leak!
 199   DropImageReference();
 200 }
 201
 202 bool DecodedSurfaceProvider::ShouldPreferSyncRun() const {
 203   return mDecoder->ShouldSyncDecode(
 204       StaticPrefs::image_mem_decode_bytes_at_a_time_AtStartup());
 205 }
 206
 207 }  // namespace image
 208 }  // namespace mozilla