Added caching of graphics effect source pixmaps to speed up effects.

If an effect is applied repeatedly on the same source, just with
varying parameters, we can save a lot by caching the source pixmaps.

Reviewed-by: Bjørn Erik Nilsen

3 files changed, 30 insertions, 2 deletions

diff --git a/src/gui/effects/qgraphicseffect.cpp b/src/gui/effects/qgraphicseffect.cpp
index 91641b0..96d35b0 100644
--- a/src/gui/effects/qgraphicseffect.cpp
+++ b/src/gui/effects/qgraphicseffect.cpp
@@ -253,7 +253,24 @@ bool QGraphicsEffectSource::isPixmap() const
 */
 QPixmap QGraphicsEffectSource::pixmap(Qt::CoordinateSystem system, QPoint *offset) const
 {
-    return d_func()->pixmap(system, offset);
+    Q_D(const QGraphicsEffectSource);
+
+    QPixmap pm;
+    if (d->m_cachedSystem == system)
+        QPixmapCache::find(d->m_cacheKey, &pm);
+
+    if (pm.isNull()) {
+        pm = d->pixmap(system, &d->m_cachedOffset);
+        d->m_cachedSystem = system;
+
+        d->invalidateCache();
+        d->m_cacheKey = QPixmapCache::insert(pm);
+    }
+
+    if (offset)
+        *offset = d->m_cachedOffset;
+
+    return pm;
 }
 
 /*!
diff --git a/src/gui/effects/qgraphicseffect.h b/src/gui/effects/qgraphicseffect.h
index c5d3ede..c89851e 100644
--- a/src/gui/effects/qgraphicseffect.h
+++ b/src/gui/effects/qgraphicseffect.h
@@ -87,6 +87,7 @@ private:
     friend class QGraphicsEffectPrivate;
     friend class QGraphicsScenePrivate;
     friend class QGraphicsItem;
+    friend class QGraphicsItemPrivate;
     friend class QWidget;
     friend class QWidgetPrivate;
 };
diff --git a/src/gui/effects/qgraphicseffect_p.h b/src/gui/effects/qgraphicseffect_p.h
index ff2fb85..8fb55d8 100644
--- a/src/gui/effects/qgraphicseffect_p.h
+++ b/src/gui/effects/qgraphicseffect_p.h
@@ -55,6 +55,8 @@
 
 #include "qgraphicseffect.h"
 
+#include <QPixmapCache>
+
 #include <private/qobject_p.h>
 #include <private/qpixmapfilter_p.h>
 
@@ -65,7 +67,7 @@ class QGraphicsEffectSourcePrivate : public QObjectPrivate
     Q_DECLARE_PUBLIC(QGraphicsEffectSource)
 public:
     QGraphicsEffectSourcePrivate() : QObjectPrivate() {}
-    virtual ~QGraphicsEffectSourcePrivate() {}
+    virtual ~QGraphicsEffectSourcePrivate() { invalidateCache(); }
     virtual void detach() = 0;
     virtual QRectF boundingRect(Qt::CoordinateSystem system) const = 0;
     virtual QRect deviceRect() const = 0;
@@ -77,9 +79,16 @@ public:
     virtual bool isPixmap() const = 0;
     virtual QPixmap pixmap(Qt::CoordinateSystem system, QPoint *offset = 0) const = 0;
     virtual void effectBoundingRectChanged() = 0;
+    void invalidateCache() const { QPixmapCache::remove(m_cacheKey); }
+
     friend class QGraphicsScenePrivate;
     friend class QGraphicsItem;
     friend class QGraphicsItemPrivate;
+
+private:
+    mutable Qt::CoordinateSystem m_cachedSystem;
+    mutable QPoint m_cachedOffset;
+    mutable QPixmapCache::Key m_cacheKey;
 };
 
 class Q_GUI_EXPORT QGraphicsEffectPrivate : public QObjectPrivate
@@ -94,6 +103,7 @@ public:
         if (source) {
             flags |= QGraphicsEffect::SourceDetached;
             source->d_func()->detach();
+            source->d_func()->invalidateCache();
             delete source;
         }
         source = newSource;