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, 215 insertions, 0 deletions

diff --git a/src/openvg/qvgimagepool.cpp b/src/openvg/qvgimagepool.cpp
new file mode 100644
index 0000000..93e6e03
--- /dev/null
+++ b/src/openvg/qvgimagepool.cpp
@@ -0,0 +1,215 @@
+/****************************************************************************
+**
+** 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.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qvgimagepool_p.h"
+#include "qpixmapdata_vg_p.h"
+
+QT_BEGIN_NAMESPACE
+
+static QVGImagePool *qt_vg_image_pool = 0;
+
+class QVGImagePoolPrivate
+{
+public:
+    QVGImagePoolPrivate() : lruFirst(0), lruLast(0) {}
+
+    QVGPixmapData *lruFirst;
+    QVGPixmapData *lruLast;
+};
+
+QVGImagePool::QVGImagePool()
+    : d_ptr(new QVGImagePoolPrivate())
+{
+}
+
+QVGImagePool::~QVGImagePool()
+{
+}
+
+QVGImagePool *QVGImagePool::instance()
+{
+    if (!qt_vg_image_pool)
+        qt_vg_image_pool = new QVGImagePool();
+    return qt_vg_image_pool;
+}
+
+void QVGImagePool::setImagePool(QVGImagePool *pool)
+{
+    if (qt_vg_image_pool != pool)
+        delete qt_vg_image_pool;
+    qt_vg_image_pool = pool;
+}
+
+VGImage QVGImagePool::createTemporaryImage(VGImageFormat format,
+                                           VGint width, VGint height,
+                                           VGbitfield allowedQuality,
+                                           QVGPixmapData *keepData)
+{
+    VGImage image;
+    do {
+        image = vgCreateImage(format, width, height, allowedQuality);
+        if (image != VG_INVALID_HANDLE)
+            return image;
+    } while (reclaimSpace(format, width, height, keepData));
+    qWarning("QVGImagePool: cannot reclaim sufficient space for a %dx%d temporary image",
+             width, height);
+    return VG_INVALID_HANDLE;
+}
+
+VGImage QVGImagePool::createImageForPixmap(VGImageFormat format,
+                                           VGint width, VGint height,
+                                           VGbitfield allowedQuality,
+                                           QVGPixmapData *data)
+{
+    VGImage image;
+    do {
+        image = vgCreateImage(format, width, height, allowedQuality);
+        if (image != VG_INVALID_HANDLE) {
+            if (data)
+                moveToHeadOfLRU(data);
+            return image;
+        }
+    } while (reclaimSpace(format, width, height, data));
+    qWarning("QVGImagePool: cannot reclaim sufficient space for a %dx%d pixmap",
+             width, height);
+    return VG_INVALID_HANDLE;
+}
+
+VGImage QVGImagePool::createPermanentImage(VGImageFormat format,
+                                           VGint width, VGint height,
+                                           VGbitfield allowedQuality)
+{
+    VGImage image;
+    do {
+        image = vgCreateImage(format, width, height, allowedQuality);
+        if (image != VG_INVALID_HANDLE)
+            return image;
+    } while (reclaimSpace(format, width, height, 0));
+    qWarning("QVGImagePool: cannot reclaim sufficient space for a %dx%d image",
+             width, height);
+    return VG_INVALID_HANDLE;
+}
+
+void QVGImagePool::releaseImage(QVGPixmapData *data, VGImage image)
+{
+    // Very simple strategy at the moment: just destroy the image.
+    if (data)
+        removeFromLRU(data);
+    vgDestroyImage(image);
+}
+
+void QVGImagePool::useImage(QVGPixmapData *data)
+{
+    moveToHeadOfLRU(data);
+}
+
+void QVGImagePool::detachImage(QVGPixmapData *data)
+{
+    removeFromLRU(data);
+}
+
+bool QVGImagePool::reclaimSpace(VGImageFormat format,
+                                VGint width, VGint height,
+                                QVGPixmapData *data)
+{
+    Q_UNUSED(format);   // For future use in picking the best image to eject.
+    Q_UNUSED(width);
+    Q_UNUSED(height);
+
+    if (data)
+        moveToHeadOfLRU(data);
+
+    QVGPixmapData *lrudata = pixmapLRU();
+    if (lrudata && lrudata != data) {
+        lrudata->reclaimImages();
+        return true;
+    }
+
+    return false;
+}
+
+void QVGImagePool::hibernate()
+{
+    // Nothing to do here at the moment since the pool does not
+    // retain VGImage's after they have been released.
+}
+
+void QVGImagePool::moveToHeadOfLRU(QVGPixmapData *data)
+{
+    Q_D(QVGImagePool);
+    if (data->inLRU) {
+        if (!data->prevLRU)
+            return;     // Already at the head of the list.
+        removeFromLRU(data);
+    }
+    data->inLRU = true;
+    data->nextLRU = d->lruFirst;
+    data->prevLRU = 0;
+    if (d->lruFirst)
+        d->lruFirst->prevLRU = data;
+    else
+        d->lruLast = data;
+    d->lruFirst = data;
+}
+
+void QVGImagePool::removeFromLRU(QVGPixmapData *data)
+{
+    Q_D(QVGImagePool);
+    if (!data->inLRU)
+        return;
+    if (data->nextLRU)
+        data->nextLRU->prevLRU = data->prevLRU;
+    else
+        d->lruLast = data->prevLRU;
+    if (data->prevLRU)
+        data->prevLRU->nextLRU = data->nextLRU;
+    else
+        d->lruFirst = data->nextLRU;
+    data->inLRU = false;
+}
+
+QVGPixmapData *QVGImagePool::pixmapLRU()
+{
+    Q_D(QVGImagePool);
+    return d->lruLast;
+}
+
+QT_END_NAMESPACE