image/ISurfaceProvider.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 objects which can either store a surface or dynamically
   8  * generate one, and various implementations.
   9  */
  10
  11 #ifndef mozilla_image_ISurfaceProvider_h
  12 #define mozilla_image_ISurfaceProvider_h
  13
  14 #include "mozilla/Attributes.h"
  15 #include "mozilla/Maybe.h"
  16 #include "mozilla/MemoryReporting.h"
  17 #include "mozilla/NotNull.h"
  18 #include "mozilla/TimeStamp.h"
  19 #include "mozilla/Variant.h"
  20 #include "mozilla/gfx/2D.h"
  21
  22 #include "imgFrame.h"
  23 #include "SurfaceCache.h"
  24
  25 namespace mozilla {
  26 namespace image {
  27
  28 class CachedSurface;
  29 class DrawableSurface;
  30
  31 /**
  32  * An interface for objects which can either store a surface or dynamically
  33  * generate one.
  34  */
  35 class ISurfaceProvider {
  36  public:
  37   // Subclasses may or may not be XPCOM classes, so we just require that they
  38   // implement AddRef and Release.
  39   NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
  40
  41   /// @return key data used for identifying which image this ISurfaceProvider is
  42   /// associated with in the surface cache.
  43   ImageKey GetImageKey() const { return mImageKey; }
  44
  45   /// @return key data used to uniquely identify this ISurfaceProvider's cache
  46   /// entry in the surface cache.
  47   const SurfaceKey& GetSurfaceKey() const { return mSurfaceKey; }
  48
  49   /// @return a (potentially lazily computed) drawable reference to a surface.
  50   virtual DrawableSurface Surface();
  51
  52   /// @return true if DrawableRef() will return a completely decoded surface.
  53   virtual bool IsFinished() const = 0;
  54
  55   /// @return true if the underlying decoder is currently fully decoded. For
  56   /// animated images, this means that at least every frame has been decoded
  57   /// at least once. It does not guarantee that all of the frames are present,
  58   /// as the surface provider has the option to discard as it deems necessary.
  59   virtual bool IsFullyDecoded() const { return IsFinished(); }
  60
  61   /// @return the number of bytes of memory this ISurfaceProvider is expected to
  62   /// require. Optimizations may result in lower real memory usage. Trivial
  63   /// overhead is ignored. Because this value is used in bookkeeping, it's
  64   /// important that it be constant over the lifetime of this object.
  65   virtual size_t LogicalSizeInBytes() const = 0;
  66
  67   typedef imgFrame::AddSizeOfCbData AddSizeOfCbData;
  68   typedef imgFrame::AddSizeOfCb AddSizeOfCb;
  69
  70   /// @return the actual number of bytes of memory this ISurfaceProvider is
  71   /// using. May vary over the lifetime of the ISurfaceProvider. The default
  72   /// implementation is appropriate for static ISurfaceProviders.
  73   virtual void AddSizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
  74                                       const AddSizeOfCb& aCallback) {
  75     DrawableFrameRef ref = DrawableRef(/* aFrame = */ 0);
  76     if (!ref) {
  77       return;
  78     }
  79
  80     ref->AddSizeOfExcludingThis(aMallocSizeOf, aCallback);
  81   }
  82
  83   virtual void Reset() {}
  84   virtual void Advance(size_t aFrame) {}
  85
  86   /// @return the availability state of this ISurfaceProvider, which indicates
  87   /// whether DrawableRef() could successfully return a surface. Should only be
  88   /// called from SurfaceCache code as it relies on SurfaceCache for
  89   /// synchronization.
  90   AvailabilityState& Availability() { return mAvailability; }
  91   const AvailabilityState& Availability() const { return mAvailability; }
  92
  93  protected:
  94   ISurfaceProvider(const ImageKey aImageKey, const SurfaceKey& aSurfaceKey,
  95                    AvailabilityState aAvailability)
  96       : mImageKey(aImageKey),
  97         mSurfaceKey(aSurfaceKey),
  98         mAvailability(aAvailability) {
  99     MOZ_ASSERT(aImageKey, "Must have a valid image key");
 100   }
 101
 102   virtual ~ISurfaceProvider() {}
 103
 104   /// @return an eagerly computed drawable reference to a surface. For
 105   /// dynamically generated animation surfaces, @aFrame specifies the 0-based
 106   /// index of the desired frame.
 107   virtual DrawableFrameRef DrawableRef(size_t aFrame) = 0;
 108
 109   /// @return an imgFrame at the 0-based index of the desired frame, as
 110   /// specified by @aFrame. Only applies for animated images.
 111   virtual already_AddRefed<imgFrame> GetFrame(size_t aFrame) {
 112     MOZ_ASSERT_UNREACHABLE("Surface provider does not support direct access!");
 113     return nullptr;
 114   }
 115
 116   /// @return true if this ISurfaceProvider is locked. (@see SetLocked())
 117   /// Should only be called from SurfaceCache code as it relies on SurfaceCache
 118   /// for synchronization.
 119   virtual bool IsLocked() const = 0;
 120
 121   /// If @aLocked is true, hint that this ISurfaceProvider is in use and it
 122   /// should avoid releasing its resources. Should only be called from
 123   /// SurfaceCache code as it relies on SurfaceCache for synchronization.
 124   virtual void SetLocked(bool aLocked) = 0;
 125
 126  private:
 127   friend class CachedSurface;
 128   friend class DrawableSurface;
 129
 130   const ImageKey mImageKey;
 131   const SurfaceKey mSurfaceKey;
 132   AvailabilityState mAvailability;
 133 };
 134
 135 /**
 136  * A reference to a surface (stored in an imgFrame) that holds the surface in
 137  * memory, guaranteeing that it can be drawn. If you have a DrawableSurface
 138  * |surf| and |if (surf)| returns true, then calls to |surf->Draw()| and
 139  * |surf->GetSourceSurface()| are guaranteed to succeed.
 140  *
 141  * Note that the surface may be computed lazily, so a DrawableSurface should not
 142  * be dereferenced (i.e., operator->() should not be called) until you're
 143  * sure that you want to draw it.
 144  */
 145 class MOZ_STACK_CLASS DrawableSurface final {
 146  public:
 147   DrawableSurface() : mHaveSurface(false) {}
 148
 149   explicit DrawableSurface(DrawableFrameRef&& aDrawableRef)
 150       : mDrawableRef(std::move(aDrawableRef)),
 151         mHaveSurface(bool(mDrawableRef)) {}
 152
 153   explicit DrawableSurface(NotNull<ISurfaceProvider*> aProvider)
 154       : mProvider(aProvider), mHaveSurface(true) {}
 155
 156   DrawableSurface(DrawableSurface&& aOther)
 157       : mDrawableRef(std::move(aOther.mDrawableRef)),
 158         mProvider(std::move(aOther.mProvider)),
 159         mHaveSurface(aOther.mHaveSurface) {
 160     aOther.mHaveSurface = false;
 161   }
 162
 163   DrawableSurface& operator=(DrawableSurface&& aOther) {
 164     MOZ_ASSERT(this != &aOther, "Self-moves are prohibited");
 165     mDrawableRef = std::move(aOther.mDrawableRef);
 166     mProvider = std::move(aOther.mProvider);
 167     mHaveSurface = aOther.mHaveSurface;
 168     aOther.mHaveSurface = false;
 169     return *this;
 170   }
 171
 172   /**
 173    * If this DrawableSurface is dynamically generated from an animation, attempt
 174    * to seek to frame @aFrame, where @aFrame is a 0-based index into the frames
 175    * of the animation. Otherwise, nothing will blow up at runtime, but we assert
 176    * in debug builds, since calling this in an unexpected situation probably
 177    * indicates a bug.
 178    *
 179    * @return a successful result if we could obtain frame @aFrame. Note that
 180    * |mHaveSurface| being true means that we're guaranteed to have *some* frame,
 181    * so the caller can dereference this DrawableSurface even if Seek() fails,
 182    * but while nothing will blow up, the frame won't be the one they expect.
 183    */
 184   nsresult Seek(size_t aFrame) {
 185     MOZ_ASSERT(mHaveSurface, "Trying to seek an empty DrawableSurface?");
 186
 187     if (!mProvider) {
 188       MOZ_ASSERT_UNREACHABLE("Trying to seek a static DrawableSurface?");
 189       return NS_ERROR_FAILURE;
 190     }
 191
 192     mDrawableRef = mProvider->DrawableRef(aFrame);
 193
 194     return mDrawableRef ? NS_OK : NS_ERROR_FAILURE;
 195   }
 196
 197   already_AddRefed<imgFrame> GetFrame(size_t aFrame) {
 198     MOZ_ASSERT(mHaveSurface, "Trying to get on an empty DrawableSurface?");
 199
 200     if (!mProvider) {
 201       MOZ_ASSERT_UNREACHABLE("Trying to get on a static DrawableSurface?");
 202       return nullptr;
 203     }
 204
 205     return mProvider->GetFrame(aFrame);
 206   }
 207
 208   void Reset() {
 209     if (!mProvider) {
 210       MOZ_ASSERT_UNREACHABLE("Trying to reset a static DrawableSurface?");
 211       return;
 212     }
 213
 214     mProvider->Reset();
 215   }
 216
 217   void Advance(size_t aFrame) {
 218     if (!mProvider) {
 219       MOZ_ASSERT_UNREACHABLE("Trying to advance a static DrawableSurface?");
 220       return;
 221     }
 222
 223     mProvider->Advance(aFrame);
 224   }
 225
 226   bool IsFullyDecoded() const {
 227     if (!mProvider) {
 228       MOZ_ASSERT_UNREACHABLE(
 229           "Trying to check decoding state of a static DrawableSurface?");
 230       return false;
 231     }
 232
 233     return mProvider->IsFullyDecoded();
 234   }
 235
 236   explicit operator bool() const { return mHaveSurface; }
 237   imgFrame* operator->() { return DrawableRef().get(); }
 238
 239  private:
 240   DrawableSurface(const DrawableSurface& aOther) = delete;
 241   DrawableSurface& operator=(const DrawableSurface& aOther) = delete;
 242
 243   DrawableFrameRef& DrawableRef() {
 244     MOZ_ASSERT(mHaveSurface);
 245
 246     // If we weren't created with a DrawableFrameRef directly, we should've been
 247     // created with an ISurfaceProvider which can give us one. Note that if
 248     // Seek() has been called, we'll already have a DrawableFrameRef, so we
 249     // won't need to get one here.
 250     if (!mDrawableRef) {
 251       MOZ_ASSERT(mProvider);
 252       mDrawableRef = mProvider->DrawableRef(/* aFrame = */ 0);
 253     }
 254
 255     MOZ_ASSERT(mDrawableRef);
 256     return mDrawableRef;
 257   }
 258
 259   DrawableFrameRef mDrawableRef;
 260   RefPtr<ISurfaceProvider> mProvider;
 261   bool mHaveSurface;
 262 };
 263
 264 // Surface() is implemented here so that DrawableSurface's definition is
 265 // visible. This default implementation eagerly obtains a DrawableFrameRef for
 266 // the first frame and is intended for static ISurfaceProviders.
 267 inline DrawableSurface ISurfaceProvider::Surface() {
 268   return DrawableSurface(DrawableRef(/* aFrame = */ 0));
 269 }
 270
 271 /**
 272  * An ISurfaceProvider that stores a single surface.
 273  */
 274 class SimpleSurfaceProvider final : public ISurfaceProvider {
 275  public:
 276   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SimpleSurfaceProvider, override)
 277
 278   SimpleSurfaceProvider(const ImageKey aImageKey, const SurfaceKey& aSurfaceKey,
 279                         NotNull<imgFrame*> aSurface)
 280       : ISurfaceProvider(aImageKey, aSurfaceKey,
 281                          AvailabilityState::StartAvailable()),
 282         mSurface(aSurface) {
 283     MOZ_ASSERT(aSurfaceKey.Size() == mSurface->GetSize());
 284   }
 285
 286   bool IsFinished() const override { return mSurface->IsFinished(); }
 287
 288   size_t LogicalSizeInBytes() const override {
 289     gfx::IntSize size = mSurface->GetSize();
 290     return size.width * size.height * mSurface->GetBytesPerPixel();
 291   }
 292
 293  protected:
 294   DrawableFrameRef DrawableRef(size_t aFrame) override {
 295     MOZ_ASSERT(aFrame == 0,
 296                "Requesting an animation frame from a SimpleSurfaceProvider?");
 297     return mSurface->DrawableRef();
 298   }
 299
 300   bool IsLocked() const override { return bool(mLockRef); }
 301
 302   void SetLocked(bool aLocked) override {
 303     if (aLocked == IsLocked()) {
 304       return;  // Nothing changed.
 305     }
 306
 307     // If we're locked, hold a DrawableFrameRef to |mSurface|, which will keep
 308     // any volatile buffer it owns in memory.
 309     mLockRef = aLocked ? mSurface->DrawableRef() : DrawableFrameRef();
 310   }
 311
 312  private:
 313   virtual ~SimpleSurfaceProvider() {}
 314
 315   NotNull<RefPtr<imgFrame>> mSurface;
 316   DrawableFrameRef mLockRef;
 317 };
 318
 319 }  // namespace image
 320 }  // namespace mozilla
 321
 322 #endif  // mozilla_image_ISurfaceProvider_h