Add an image allocation pool to the OpenVG paint engine

Some OpenVG GPU's have limitations on the amount of memory
available to create VGImage's.  When the memory runs out,
vgCreateImage() will fail.

This change introduces QVGImagePool, which keeps track of all
QVGPixmapData image allocations and ejects least-recently-used
pixmaps when GPU memory is exhausted.

Task-number: QT-2554
Reviewed-by: trustme

1 files changed, 157 insertions, 0 deletions

diff --git a/src/openvg/qvgimagepool_p.h b/src/openvg/qvgimagepool_p.h
new file mode 100644
index 0000000..66a4998
--- /dev/null
+++ b/src/openvg/qvgimagepool_p.h
@@ -0,0 +1,157 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtOpenVG module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QVGIMAGEPOOL_P_H
+#define QVGIMAGEPOOL_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of other Qt classes.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qvg.h"
+#include <QtCore/qscopedpointer.h>
+
+QT_BEGIN_NAMESPACE
+
+class QVGPixmapData;
+class QVGImagePoolPrivate;
+
+class Q_OPENVG_EXPORT QVGImagePool
+{
+public:
+    QVGImagePool();
+    virtual ~QVGImagePool();
+
+    static QVGImagePool *instance();
+
+    // This function can be used from system-specific graphics system
+    // plugins to alter the image allocation strategy.
+    static void setImagePool(QVGImagePool *pool);
+
+    // Create a new VGImage from the pool with the specified parameters
+    // that is not associated with a pixmap.  The VGImage is returned to
+    // the pool when releaseImage() is called.
+    //
+    // This function will call reclaimSpace() when vgCreateImage() fails.
+    //
+    // This function is typically called when allocating temporary
+    // VGImage's for pixmap filters.  The "keepData" object will not
+    // be reclaimed if reclaimSpace() needs to be called.
+    virtual VGImage createTemporaryImage(VGImageFormat format,
+                                         VGint width, VGint height,
+                                         VGbitfield allowedQuality,
+                                         QVGPixmapData *keepData = 0);
+
+    // Create a new VGImage with the specified parameters and associate
+    // it with "data".  The QVGPixmapData will be notified when the
+    // VGImage needs to be reclaimed by the pool.
+    //
+    // This function will call reclaimSpace() when vgCreateImage() fails.
+    virtual VGImage createImageForPixmap(VGImageFormat format,
+                                         VGint width, VGint height,
+                                         VGbitfield allowedQuality,
+                                         QVGPixmapData *data);
+
+    // Create a permanent VGImage with the specified parameters.
+    // If there is insufficient space for the vgCreateImage call,
+    // then this function will call reclaimSpace() and try again.
+    //
+    // The caller is responsible for calling vgDestroyImage()
+    // when it no longer needs the VGImage, as the image is not
+    // recorded in the image pool.
+    //
+    // This function is typically used for pattern brushes where
+    // the OpenVG engine is responsible for managing the lifetime
+    // of the VGImage, destroying it automatically when the brush
+    // is no longer in use.
+    virtual VGImage createPermanentImage(VGImageFormat format,
+                                         VGint width, VGint height,
+                                         VGbitfield allowedQuality);
+
+    // Release a VGImage that is no longer required.
+    virtual void releaseImage(QVGPixmapData *data, VGImage image);
+
+    // Notify the pool that a QVGPixmapData object is using
+    // an image again.  This allows the pool to move the image
+    // within a least-recently-used list of QVGPixmapData objects.
+    virtual void useImage(QVGPixmapData *data);
+
+    // Notify the pool that the VGImage's associated with a
+    // QVGPixmapData are being detached from the pool.  The caller
+    // will become responsible for calling vgDestroyImage().
+    virtual void detachImage(QVGPixmapData *data);
+
+    // Reclaim space for an image allocation with the specified parameters.
+    // Returns true if space was reclaimed, or false if there is no
+    // further space that can be reclaimed.  The "data" parameter
+    // indicates the pixmap that is trying to obtain space which should
+    // not itself be reclaimed.
+    virtual bool reclaimSpace(VGImageFormat format,
+                              VGint width, VGint height,
+                              QVGPixmapData *data);
+
+    // Hibernate the image pool because the context is about to be
+    // destroyed.  All VGImage's left in the pool should be released.
+    virtual void hibernate();
+
+protected:
+    // Helper functions for managing the LRU list of QVGPixmapData objects.
+    void moveToHeadOfLRU(QVGPixmapData *data);
+    void removeFromLRU(QVGPixmapData *data);
+    QVGPixmapData *pixmapLRU();
+
+private:
+    QScopedPointer<QVGImagePoolPrivate> d_ptr;
+
+    Q_DECLARE_PRIVATE(QVGImagePool)
+    Q_DISABLE_COPY(QVGImagePool)
+};
+
+QT_END_NAMESPACE
+
+#endif