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  #include "qplatformsharedgraphicscache.h"
  
  QT_BEGIN_NAMESPACE
  
  /*!
      \class QPlatformSharedGraphicsCache
      \since 5.0
      \internal
      \preliminary
      \ingroup qpa
      \brief The QPlatformSharedGraphicsCache is an abstraction of a cross-process graphics cache.
  
      If supported, it is possible to retrieve a QPlatformSharedGraphicsCache object from the
      platform integration. This is typically used to store graphical items which should be shared
      between several processes.
  
      Items are requested from the cache by calling requestItems(). If the cache contains the
      requested items in the requested cache, the itemsAvailable() signal is emitted with the ID of
      the graphical buffer and each item's coordinates inside the buffer. Before requesting items
      from a cache, the user must call ensureCacheInitialized() to set the correct parameters for
      the cache.
  
      If the cache does not yet contain the requested items, it will emit a similar itemsMissing()
      signal. The client can then call updateItems() with rasterizations of the items and they will be
      entered into the shared cache. As the items are rendered into the cache, itemsAvailable() signals
      will be emitted for each of the items which have previously been requested and which have not
      yet been reported as ready.
  
      Using beginRequestBatch() and endRequestBatch(), it's possible to batch glyph requests, which
      could improve performance in cases where you have a sequence of requests pending, and you
      do not need the results during this sequence.
  */
  
  /*!
      \enum QPlatformSharedGraphicsCache::BufferType
  
      Defines how the type of buffer required to contain a cache.
  
      \value OpenGLTexture The buffer will be allocated in graphics memory, and an OpenGL texture
                           for a buffer belonging to the cache can be requested using
                           textureIdForBuffer().
  */
  
  /*!
      \enum QPlatformSharedGraphicsCache::PixelFormat
  
      Defines the pixel format of a cache.
  
      \value Alpha8 The cache will use 8 bits to represent the alpha value of each pixel. If an
                    OpenGL texture is created for a buffer belong to the cache, it will have the
                    pixel format GL_ALPHA.
  */
  
  /*!
     \fn void QPlatformSharedGraphicsCache::ensureCacheInitialized(const QByteArray &cacheId, BufferType bufferType, PixelFormat pixelFormat)
  
     Initializes a cache named \a cacheId if it has not yet been initialized. The \a bufferType and
     \a pixelFormat gives the format of the buffers that will be used to contain the items in the
     cache. If a cache with the same \a cacheId has previously been initialized, the call will be
     ignored. The cache will keep its previously set buffer type and pixel format.
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::requestItems(const QByteArray &cacheId, const QVector<quint32> &itemIds)
  
      Requests all the items in \a itemIds from the cache with the name \a cacheId.
  
      If any or all of the items are available in the cache, one or more itemsAvailable() signals will be
      emitted corresponding to the items. If the cache does not contain all of the items in question,
      then an itemsMissing() signal will be emitted corresponding to the missing items. The user
      is at this point expected to call insertItems() to insert the missing items into the cache. If
      the inserted items have previously been requested by the user, at which point an itemsAvailable()
      signal will be emitted corresponding to the items.
  
      Before requesting items from a cache, the user must call ensureCacheInitialized() with the
      correct parameters for the cache.
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::insertItems(const QByteArray &cacheId, const QVector<quint32> &itemIds, const QVector<QImage> &items)
  
      Inserts the items in \a itemIds into the cache named \a cacheId. The appearance of
      each item is stored in \a items. The format of the QImage objects is expected to match the
      pixel format of the cache as it was initialized in ensureCacheInitialized().
  
      When the items have been successfully entered into the cache, one or more itemsAvailable() signals
      will be emitted for the items.
  
      If the cache already contains the items, the behavior is implementation-specific. The
      implementation may choose to ignore the items or it may overwrite the existing instances in
      the cache. Either way, itemsAvailable() signals corresponding to the inserted items will be
      emitted.
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::releaseItems(const QByteArray &cacheId, const QVector<quint32> &itemIds)
  
      Releases the reference to the items in \a itemIds from the cache named \a cacheId. This should
      only be called when all references to the items have been released by the user, and they are no
      longer needed.
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::itemsMissing(const QByteArray &cacheId, const QVector<quint32> &itemIds)
  
      This signal is emitted when requestItems() has been called for one or more items in the
      cache named \a cacheId which are not yet available in the cache. The user is then expected to
      call insertItems() to update the cache with the respective items, at which point they will
      become available to all clients of the shared cache.
  
      The vector \a itemIds contains the IDs of the items that need to be inserted into the cache.
  
      \sa itemsAvailable(), insertItems(), requestItems()
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::itemsAvailable(const QByteArray &cacheId, void *bufferId, const QVector<quint32> &itemIds, const QVector<QPoint> &positionsInBuffer)
  
      This signal can be emitted at any time when either requestItems() or insertItems() has been
      called by the application for one or more items in the cache named \a cacheId, as long as
      releaseItems() has not subsequently been called for the same items. It instructs the application
      on where to find the items that have been entered into the cache. When the application receives
      a buffer, it is expected to reference it using referenceBuffer() on it if it keeps a reference
      to the buffer.
  
      The \a bufferId is an ID for the buffer that contains the items. The \a bufferId can be
      converted to a format usable by the application depending on which format it was given at
      initialization. If it is a OpenGLTexture, its texture ID can be requested using the
      textureIdForBuffer() function. The dimensions of the buffer are given by \a bufferSize.
  
      The items provided by the cache are identified in the \a itemIds vector. The
      \a positionsInBuffer vector contains the locations inside the buffer of each item. Each entry in
      \a positionsInBuffer corresponds to an item in \a itemIds.
  
      The buffer and the items' locations within the buffer can be considered valid until an
      itemsInvalidated() signal has been emitted for the items, or until releaseItems() is called
      for the items.
  
      \sa itemsMissing(), requestItems(), bufferType()
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::itemsUpdated(const QByteArray &cacheId, void *bufferId, const QVector<quint32> &itemIds, const QVector<QPoint> &positionsInBuffer)
  
      This signal is similar in usage to the itemsAvailable() signal, but will be emitted when
      the location of a previously requested or inserted item has been updated. The application
      must update its data for the respective items and release any references to old buffers held
      by the items.
  
      If the application no longer holds any references to previously referenced items in a given
      cache, it should call releaseItems() for these items, at which point it will no longer receive
      any itemsUpdated() signal for these items.
  
      \sa requestItems(), insertItems(), itemsAvailable()
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::itemsInvalidated(const QByteArray &cacheId, const QVector<quint32> &itemIds)
  
      This signal is emitted when the items given by \a itemIds in the cache named \a cacheId have
      been removed from the cache and the previously reported information about them is considered
      invalid. It will only be emitted for items for which a buffer has previously been identified
      through the itemsAvailable() signal (either as response to a requestItems() call or an
      insertItems() call.)
  
      The application is expected to throw away information about the items in the \a itemIds array
      and drop any references it might have to the memory held by the buffer. If the items are still
      required by the application, it can re-commit them to the cache using the insertItems() function.
  
      If the application no longer holds any references to previously referenced items in a given
      cache, it should call releaseItems() for these items, at which point it will no longer receive
      any itemsInvalidated() signal for these items.
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::beginRequestBatch()
  
      This is a hint to the cache that a burst of requests is pending. In some implementations, this
      will improve performance, as the cache can focus on handling the requests and wait with the
      results until it is done. It should typically be called prior to a sequence of calls to
      requestItems() and releaseItems().
  
      Any call to beginRequestBatch() must be followed at some point by a call to endRequestBatch().
      Failing to do this may lead to the results of requests never being emitted.
  
      \note beginRequestBatch() and endRequestBatch() have no stacking logic. Calling
      beginRequestBatch() twice in a row has no effect, and the single existing batch will be ended
      by the earliest call to endRequestBatch().
  
      \sa endRequestBatch(), requestBatchStarted()
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::endRequestBatch()
  
      Signals to the cache that the request sequence which has previously been commenced using
      beginRequestBatch() has now finished.
  
      \sa beginRequestBatch(), requestBatchStarted()
  */
  
  /*!
     \fn bool QPlatformSharedGraphicsCache::requestBatchStarted() const
  
     Returns \c true if a request batch has previously been started using beginRequestBatch()
     and not yet stopped using endRequestBatch().
  
     \sa beginRequestBatch(), endRequestBatch()
  */
  
  /*!
      \fn uint QPlatformSharedGraphicsCache::textureIdForBuffer(void *bufferId)
  
      Returns an OpenGL texture ID corresponding to the buffer \a bufferId, which has previously
      been passed through signals itemsAvailable() or itemsUpdated(). The relevant OpenGL context
      should be current when calling this function.
  
      \sa eglImageForBuffer(), sizeOfBuffer()
  */
  
  /*!
      \fn void *QPlatformSharedGraphicsCache::eglImageForBuffer(void *bufferId)
  
      Returns an EGLImageKHR image corresponding to the buffer \a bufferId.
  
      \sa textureIdForBuffer(), sizeOfBuffer()
  */
  
  /*!
      \fn void QPlatformSharedGraphicsCache::referenceBuffer(void *bufferId)
  
      Registers a reference to the buffer \a bufferId.
  
      \sa dereferenceBuffer()
  */
  
  /*!
      \fn bool QPlatformSharedGraphicsCache::dereferenceBuffer(void *bufferId)
  
      Removed a previously registered reference to the buffer \a bufferId. Returns \c true if there
      are still more references to the buffer in question, or false if this was the last reference
      (in which case the buffer may have been deleted in the cache.)
  
      \sa dereferenceBuffer()
  */
  
  /*!
      \fn QSize QPlatformSharedGraphicsCache::sizeOfBuffer(void *bufferId)
  
      Returns the size of the buffer \a bufferId.
  
      \sa textureIdForBuffer(), eglImageForBuffer()
  */
  
  QT_END_NAMESPACE
  