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