1 /****************************************************************************
3 ** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
4 ** Contact: http://www.qt-project.org/legal
6 ** This file is part of the QtGui module of the Qt Toolkit.
8 ** $QT_BEGIN_LICENSE:LGPL$
9 ** Commercial License Usage
10 ** Licensees holding valid commercial Qt licenses may use this file in
11 ** accordance with the commercial license agreement provided with the
12 ** Software or, alternatively, in accordance with the terms contained in
13 ** a written agreement between you and Digia. For licensing terms and
14 ** conditions see http://qt.digia.com/licensing. For further information
15 ** use the contact form at http://qt.digia.com/contact-us.
17 ** GNU Lesser General Public License Usage
18 ** Alternatively, this file may be used under the terms of the GNU Lesser
19 ** General Public License version 2.1 as published by the Free Software
20 ** Foundation and appearing in the file LICENSE.LGPL included in the
21 ** packaging of this file. Please review the following information to
22 ** ensure the GNU Lesser General Public License version 2.1 requirements
23 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
25 ** In addition, as a special exception, Digia gives you certain additional
26 ** rights. These rights are described in the Digia Qt LGPL Exception
27 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
29 ** GNU General Public License Usage
30 ** Alternatively, this file may be used under the terms of the GNU
31 ** General Public License version 3.0 as published by the Free Software
32 ** Foundation and appearing in the file LICENSE.GPL included in the
33 ** packaging of this file. Please review the following information to
34 ** ensure the GNU General Public License version 3.0 requirements will be
35 ** met: http://www.gnu.org/copyleft/gpl.html.
40 ****************************************************************************/
42 #include "qplatformsharedgraphicscache.h"
47 \class QPlatformSharedGraphicsCache
52 \brief The QPlatformSharedGraphicsCache is an abstraction of a cross-process graphics cache.
54 If supported, it is possible to retrieve a QPlatformSharedGraphicsCache object from the
55 platform integration. This is typically used to store graphical items which should be shared
56 between several processes.
58 Items are requested from the cache by calling requestItems(). If the cache contains the
59 requested items in the requested cache, the itemsAvailable() signal is emitted with the ID of
60 the graphical buffer and each item's coordinates inside the buffer. Before requesting items
61 from a cache, the user must call ensureCacheInitialized() to set the correct parameters for
64 If the cache does not yet contain the requested items, it will emit a similar itemsMissing()
65 signal. The client can then call updateItems() with rasterizations of the items and they will be
66 entered into the shared cache. As the items are rendered into the cache, itemsAvailable() signals
67 will be emitted for each of the items which have previously been requested and which have not
68 yet been reported as ready.
70 Using beginRequestBatch() and endRequestBatch(), it's possible to batch glyph requests, which
71 could improve performance in cases where you have a sequence of requests pending, and you
72 do not need the results during this sequence.
76 \enum QPlatformSharedGraphicsCache::BufferType
78 Defines how the type of buffer required to contain a cache.
80 \value OpenGLTexture The buffer will be allocated in graphics memory, and an OpenGL texture
81 for a buffer belonging to the cache can be requested using
86 \enum QPlatformSharedGraphicsCache::PixelFormat
88 Defines the pixel format of a cache.
90 \value Alpha8 The cache will use 8 bits to represent the alpha value of each pixel. If an
91 OpenGL texture is created for a buffer belong to the cache, it will have the
92 pixel format GL_ALPHA.
96 \fn void QPlatformSharedGraphicsCache::ensureCacheInitialized(const QByteArray &cacheId, BufferType bufferType, PixelFormat pixelFormat)
98 Initializes a cache named \a cacheId if it has not yet been initialized. The \a bufferType and
99 \a pixelFormat gives the format of the buffers that will be used to contain the items in the
100 cache. If a cache with the same \a cacheId has previously been initialized, the call will be
101 ignored. The cache will keep its previously set buffer type and pixel format.
105 \fn void QPlatformSharedGraphicsCache::requestItems(const QByteArray &cacheId, const QVector<quint32> &itemIds)
107 Requests all the items in \a itemIds from the cache with the name \a cacheId.
109 If any or all of the items are available in the cache, one or more itemsAvailable() signals will be
110 emitted corresponding to the items. If the cache does not contain all of the items in question,
111 then an itemsMissing() signal will be emitted corresponding to the missing items. The user
112 is at this point expected to call insertItems() to insert the missing items into the cache. If
113 the inserted items have previously been requested by the user, at which point an itemsAvailable()
114 signal will be emitted corresponding to the items.
116 Before requesting items from a cache, the user must call ensureCacheInitialized() with the
117 correct parameters for the cache.
121 \fn void QPlatformSharedGraphicsCache::insertItems(const QByteArray &cacheId, const QVector<quint32> &itemIds, const QVector<QImage> &items)
123 Inserts the items in \a itemIds into the cache named \a cacheId. The appearance of
124 each item is stored in \a items. The format of the QImage objects is expected to match the
125 pixel format of the cache as it was initialized in ensureCacheInitialized().
127 When the items have been successfully entered into the cache, one or more itemsAvailable() signals
128 will be emitted for the items.
130 If the cache already contains the items, the behavior is implementation-specific. The
131 implementation may choose to ignore the items or it may overwrite the existing instances in
132 the cache. Either way, itemsAvailable() signals corresponding to the inserted items will be
137 \fn void QPlatformSharedGraphicsCache::releaseItems(const QByteArray &cacheId, const QVector<quint32> &itemIds)
139 Releases the reference to the items in \a itemIds from the cache named \a cacheId. This should
140 only be called when all references to the items have been released by the user, and they are no
145 \fn void QPlatformSharedGraphicsCache::itemsMissing(const QByteArray &cacheId, const QVector<quint32> &itemIds)
147 This signal is emitted when requestItems() has been called for one or more items in the
148 cache named \a cacheId which are not yet available in the cache. The user is then expected to
149 call insertItems() to update the cache with the respective items, at which point they will
150 become available to all clients of the shared cache.
152 The vector \a itemIds contains the IDs of the items that need to be inserted into the cache.
154 \sa itemsAvailable(), insertItems(), requestItems()
158 \fn void QPlatformSharedGraphicsCache::itemsAvailable(const QByteArray &cacheId, void *bufferId, const QVector<quint32> &itemIds, const QVector<QPoint> &positionsInBuffer)
160 This signal can be emitted at any time when either requestItems() or insertItems() has been
161 called by the application for one or more items in the cache named \a cacheId, as long as
162 releaseItems() has not subsequently been called for the same items. It instructs the application
163 on where to find the items that have been entered into the cache. When the application receives
164 a buffer, it is expected to reference it using referenceBuffer() on it if it keeps a reference
167 The \a bufferId is an ID for the buffer that contains the items. The \a bufferId can be
168 converted to a format usable by the application depending on which format it was given at
169 initialization. If it is a OpenGLTexture, its texture ID can be requested using the
170 textureIdForBuffer() function. The dimensions of the buffer are given by \a bufferSize.
172 The items provided by the cache are identified in the \a itemIds vector. The
173 \a positionsInBuffer vector contains the locations inside the buffer of each item. Each entry in
174 \a positionsInBuffer corresponds to an item in \a itemIds.
176 The buffer and the items' locations within the buffer can be considered valid until an
177 itemsInvalidated() signal has been emitted for the items, or until releaseItems() is called
180 \sa itemsMissing(), requestItems(), bufferType()
184 \fn void QPlatformSharedGraphicsCache::itemsUpdated(const QByteArray &cacheId, void *bufferId, const QVector<quint32> &itemIds, const QVector<QPoint> &positionsInBuffer)
186 This signal is similar in usage to the itemsAvailable() signal, but will be emitted when
187 the location of a previously requested or inserted item has been updated. The application
188 must update its data for the respective items and release any references to old buffers held
191 If the application no longer holds any references to previously referenced items in a given
192 cache, it should call releaseItems() for these items, at which point it will no longer receive
193 any itemsUpdated() signal for these items.
195 \sa requestItems(), insertItems(), itemsAvailable()
199 \fn void QPlatformSharedGraphicsCache::itemsInvalidated(const QByteArray &cacheId, const QVector<quint32> &itemIds)
201 This signal is emitted when the items given by \a itemIds in the cache named \a cacheId have
202 been removed from the cache and the previously reported information about them is considered
203 invalid. It will only be emitted for items for which a buffer has previously been identified
204 through the itemsAvailable() signal (either as response to a requestItems() call or an
207 The application is expected to throw away information about the items in the \a itemIds array
208 and drop any references it might have to the memory held by the buffer. If the items are still
209 required by the application, it can re-commit them to the cache using the insertItems() function.
211 If the application no longer holds any references to previously referenced items in a given
212 cache, it should call releaseItems() for these items, at which point it will no longer receive
213 any itemsInvalidated() signal for these items.
217 \fn void QPlatformSharedGraphicsCache::beginRequestBatch()
219 This is a hint to the cache that a burst of requests is pending. In some implementations, this
220 will improve performance, as the cache can focus on handling the requests and wait with the
221 results until it is done. It should typically be called prior to a sequence of calls to
222 requestItems() and releaseItems().
224 Any call to beginRequestBatch() must be followed at some point by a call to endRequestBatch().
225 Failing to do this may lead to the results of requests never being emitted.
227 \note beginRequestBatch() and endRequestBatch() have no stacking logic. Calling
228 beginRequestBatch() twice in a row has no effect, and the single existing batch will be ended
229 by the earliest call to endRequestBatch().
231 \sa endRequestBatch(), requestBatchStarted()
235 \fn void QPlatformSharedGraphicsCache::endRequestBatch()
237 Signals to the cache that the request sequence which has previously been commenced using
238 beginRequestBatch() has now finished.
240 \sa beginRequestBatch(), requestBatchStarted()
244 \fn bool QPlatformSharedGraphicsCache::requestBatchStarted() const
246 Returns true if a request batch has previously been started using beginRequestBatch()
247 and not yet stopped using endRequestBatch().
249 \sa beginRequestBatch(), endRequestBatch()
253 \fn uint QPlatformSharedGraphicsCache::textureIdForBuffer(void *bufferId)
255 Returns an OpenGL texture ID corresponding to the buffer \a bufferId, which has previously
256 been passed through signals itemsAvailable() or itemsUpdated(). The relevant OpenGL context
257 should be current when calling this function.
259 \sa eglImageForBuffer(), sizeOfBuffer()
263 \fn void *QPlatformSharedGraphicsCache::eglImageForBuffer(void *bufferId)
265 Returns an EGLImageKHR image corresponding to the buffer \a bufferId.
267 \sa textureIdForBuffer(), sizeOfBuffer()
271 \fn void QPlatformSharedGraphicsCache::referenceBuffer(void *bufferId)
273 Registers a reference to the buffer \a bufferId.
275 \sa dereferenceBuffer()
279 \fn bool QPlatformSharedGraphicsCache::dereferenceBuffer(void *bufferId)
281 Removed a previously registered reference to the buffer \a bufferId. Returns true if there
282 are still more references to the buffer in question, or false if this was the last reference
283 (in which case the buffer may have been deleted in the cache.)
285 \sa dereferenceBuffer()
289 \fn QSize QPlatformSharedGraphicsCache::sizeOfBuffer(void *bufferId)
291 Returns the size of the buffer \a bufferId.
293 \sa textureIdForBuffer(), eglImageForBuffer()