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39
40#include "qplatformsharedgraphicscache.h"
41
42QT_BEGIN_NAMESPACE
43
44/*!
45 \class QPlatformSharedGraphicsCache
46 \since 5.0
47 \internal
48 \preliminary
49 \ingroup qpa
50 \brief The QPlatformSharedGraphicsCache is an abstraction of a cross-process graphics cache.
51
52 If supported, it is possible to retrieve a QPlatformSharedGraphicsCache object from the
53 platform integration. This is typically used to store graphical items which should be shared
54 between several processes.
55
56 Items are requested from the cache by calling requestItems(). If the cache contains the
57 requested items in the requested cache, the itemsAvailable() signal is emitted with the ID of
58 the graphical buffer and each item's coordinates inside the buffer. Before requesting items
59 from a cache, the user must call ensureCacheInitialized() to set the correct parameters for
60 the cache.
61
62 If the cache does not yet contain the requested items, it will emit a similar itemsMissing()
63 signal. The client can then call updateItems() with rasterizations of the items and they will be
64 entered into the shared cache. As the items are rendered into the cache, itemsAvailable() signals
65 will be emitted for each of the items which have previously been requested and which have not
66 yet been reported as ready.
67
68 Using beginRequestBatch() and endRequestBatch(), it's possible to batch glyph requests, which
69 could improve performance in cases where you have a sequence of requests pending, and you
70 do not need the results during this sequence.
71*/
72
73/*!
74 \enum QPlatformSharedGraphicsCache::BufferType
75
76 Defines how the type of buffer required to contain a cache.
77
78 \value OpenGLTexture The buffer will be allocated in graphics memory, and an OpenGL texture
79 for a buffer belonging to the cache can be requested using
80 textureIdForBuffer().
81*/
82
83/*!
84 \enum QPlatformSharedGraphicsCache::PixelFormat
85
86 Defines the pixel format of a cache.
87
88 \value Alpha8 The cache will use 8 bits to represent the alpha value of each pixel. If an
89 OpenGL texture is created for a buffer belong to the cache, it will have the
90 pixel format GL_ALPHA.
91*/
92
93/*!
94 \fn void QPlatformSharedGraphicsCache::ensureCacheInitialized(const QByteArray &cacheId, BufferType bufferType, PixelFormat pixelFormat)
95
96 Initializes a cache named \a cacheId if it has not yet been initialized. The \a bufferType and
97 \a pixelFormat gives the format of the buffers that will be used to contain the items in the
98 cache. If a cache with the same \a cacheId has previously been initialized, the call will be
99 ignored. The cache will keep its previously set buffer type and pixel format.
100*/
101
102/*!
103 \fn void QPlatformSharedGraphicsCache::requestItems(const QByteArray &cacheId, const QList<quint32> &itemIds)
104
105 Requests all the items in \a itemIds from the cache with the name \a cacheId.
106
107 If any or all of the items are available in the cache, one or more itemsAvailable() signals will be
108 emitted corresponding to the items. If the cache does not contain all of the items in question,
109 then an itemsMissing() signal will be emitted corresponding to the missing items. The user
110 is at this point expected to call insertItems() to insert the missing items into the cache. If
111 the inserted items have previously been requested by the user, at which point an itemsAvailable()
112 signal will be emitted corresponding to the items.
113
114 Before requesting items from a cache, the user must call ensureCacheInitialized() with the
115 correct parameters for the cache.
116*/
117
118/*!
119 \fn void QPlatformSharedGraphicsCache::insertItems(const QByteArray &cacheId, const QList<quint32> &itemIds, const QList<QImage> &items)
120
121 Inserts the items in \a itemIds into the cache named \a cacheId. The appearance of
122 each item is stored in \a items. The format of the QImage objects is expected to match the
123 pixel format of the cache as it was initialized in ensureCacheInitialized().
124
125 When the items have been successfully entered into the cache, one or more itemsAvailable() signals
126 will be emitted for the items.
127
128 If the cache already contains the items, the behavior is implementation-specific. The
129 implementation may choose to ignore the items or it may overwrite the existing instances in
130 the cache. Either way, itemsAvailable() signals corresponding to the inserted items will be
131 emitted.
132*/
133
134/*!
135 \fn void QPlatformSharedGraphicsCache::releaseItems(const QByteArray &cacheId, const QList<quint32> &itemIds)
136
137 Releases the reference to the items in \a itemIds from the cache named \a cacheId. This should
138 only be called when all references to the items have been released by the user, and they are no
139 longer needed.
140*/
141
142/*!
143 \fn void QPlatformSharedGraphicsCache::itemsMissing(const QByteArray &cacheId, const QList<quint32> &itemIds)
144
145 This signal is emitted when requestItems() has been called for one or more items in the
146 cache named \a cacheId which are not yet available in the cache. The user is then expected to
147 call insertItems() to update the cache with the respective items, at which point they will
148 become available to all clients of the shared cache.
149
150 The \a itemIds list contains the IDs of the items that need to be inserted into the cache.
151
152 \sa itemsAvailable(), insertItems(), requestItems()
153*/
154
155/*!
156 \fn void QPlatformSharedGraphicsCache::itemsAvailable(const QByteArray &cacheId, void *bufferId, const QList<quint32> &itemIds, const QList<QPoint> &positionsInBuffer)
157
158 This signal can be emitted at any time when either requestItems() or insertItems() has been
159 called by the application for one or more items in the cache named \a cacheId, as long as
160 releaseItems() has not subsequently been called for the same items. It instructs the application
161 on where to find the items that have been entered into the cache. When the application receives
162 a buffer, it is expected to reference it using referenceBuffer() on it if it keeps a reference
163 to the buffer.
164
165 The \a bufferId is an ID for the buffer that contains the items. The \a bufferId can be
166 converted to a format usable by the application depending on which format it was given at
167 initialization. If it is a OpenGLTexture, its texture ID can be requested using the
168 textureIdForBuffer() function. The dimensions of the buffer are given by \a bufferSize.
169
170 The items provided by the cache are identified in the \a itemIds list. The
171 \a positionsInBuffer list contains the locations inside the buffer of each item. Each entry in
172 \a positionsInBuffer corresponds to an item in \a itemIds.
173
174 The buffer and the items' locations within the buffer can be considered valid until an
175 itemsInvalidated() signal has been emitted for the items, or until releaseItems() is called
176 for the items.
177
178 \sa itemsMissing(), requestItems(), bufferType()
179*/
180
181/*!
182 \fn void QPlatformSharedGraphicsCache::itemsUpdated(const QByteArray &cacheId, void *bufferId, const QList<quint32> &itemIds, const QList<QPoint> &positionsInBuffer)
183
184 This signal is similar in usage to the itemsAvailable() signal, but will be emitted when
185 the location of a previously requested or inserted item has been updated. The application
186 must update its data for the respective items and release any references to old buffers held
187 by the items.
188
189 If the application no longer holds any references to previously referenced items in a given
190 cache, it should call releaseItems() for these items, at which point it will no longer receive
191 any itemsUpdated() signal for these items.
192
193 \sa requestItems(), insertItems(), itemsAvailable()
194*/
195
196/*!
197 \fn void QPlatformSharedGraphicsCache::itemsInvalidated(const QByteArray &cacheId, const QList<quint32> &itemIds)
198
199 This signal is emitted when the items given by \a itemIds in the cache named \a cacheId have
200 been removed from the cache and the previously reported information about them is considered
201 invalid. It will only be emitted for items for which a buffer has previously been identified
202 through the itemsAvailable() signal (either as response to a requestItems() call or an
203 insertItems() call.)
204
205 The application is expected to throw away information about the items in the \a itemIds array
206 and drop any references it might have to the memory held by the buffer. If the items are still
207 required by the application, it can re-commit them to the cache using the insertItems() function.
208
209 If the application no longer holds any references to previously referenced items in a given
210 cache, it should call releaseItems() for these items, at which point it will no longer receive
211 any itemsInvalidated() signal for these items.
212*/
213
214/*!
215 \fn void QPlatformSharedGraphicsCache::beginRequestBatch()
216
217 This is a hint to the cache that a burst of requests is pending. In some implementations, this
218 will improve performance, as the cache can focus on handling the requests and wait with the
219 results until it is done. It should typically be called prior to a sequence of calls to
220 requestItems() and releaseItems().
221
222 Any call to beginRequestBatch() must be followed at some point by a call to endRequestBatch().
223 Failing to do this may lead to the results of requests never being emitted.
224
225 \note beginRequestBatch() and endRequestBatch() have no stacking logic. Calling
226 beginRequestBatch() twice in a row has no effect, and the single existing batch will be ended
227 by the earliest call to endRequestBatch().
228
229 \sa endRequestBatch(), requestBatchStarted()
230*/
231
232/*!
233 \fn void QPlatformSharedGraphicsCache::endRequestBatch()
234
235 Signals to the cache that the request sequence which has previously been commenced using
236 beginRequestBatch() has now finished.
237
238 \sa beginRequestBatch(), requestBatchStarted()
239*/
240
241/*!
242 \fn bool QPlatformSharedGraphicsCache::requestBatchStarted() const
243
244 Returns \c true if a request batch has previously been started using beginRequestBatch()
245 and not yet stopped using endRequestBatch().
246
247 \sa beginRequestBatch(), endRequestBatch()
248*/
249
250/*!
251 \fn uint QPlatformSharedGraphicsCache::textureIdForBuffer(void *bufferId)
252
253 Returns an OpenGL texture ID corresponding to the buffer \a bufferId, which has previously
254 been passed through signals itemsAvailable() or itemsUpdated(). The relevant OpenGL context
255 should be current when calling this function.
256
257 \sa eglImageForBuffer(), sizeOfBuffer()
258*/
259
260/*!
261 \fn void *QPlatformSharedGraphicsCache::eglImageForBuffer(void *bufferId)
262
263 Returns an EGLImageKHR image corresponding to the buffer \a bufferId.
264
265 \sa textureIdForBuffer(), sizeOfBuffer()
266*/
267
268/*!
269 \fn void QPlatformSharedGraphicsCache::referenceBuffer(void *bufferId)
270
271 Registers a reference to the buffer \a bufferId.
272
273 \sa dereferenceBuffer()
274*/
275
276/*!
277 \fn bool QPlatformSharedGraphicsCache::dereferenceBuffer(void *bufferId)
278
279 Removed a previously registered reference to the buffer \a bufferId. Returns \c true if there
280 are still more references to the buffer in question, or false if this was the last reference
281 (in which case the buffer may have been deleted in the cache.)
282
283 \sa dereferenceBuffer()
284*/
285
286/*!
287 \fn QSize QPlatformSharedGraphicsCache::sizeOfBuffer(void *bufferId)
288
289 Returns the size of the buffer \a bufferId.
290
291 \sa textureIdForBuffer(), eglImageForBuffer()
292*/
293
294QT_END_NAMESPACE
295