Added some optimizations to the blur and drop shadow GL filters.

* Use ExpandToTransparentBorderPadMode since we can use GL_CLAMP_TO_EDGE
  to clamp to the texture.

* Shrink the bounding rects reported by the blur
  and drop shadow filters (expanding by 2 * radius isn't needed).

* Use a single-pass blur for radii <= 3 to avoid the overhead of
  rendering to an FBO.

* Made the fast blur setting generate filters for only a predefined set
  of radii, and then use the actual blur radius to spread the sample
  points outwards.

* Optimized the generated program to rely less on temporary variables,
  as those seemed to not be handled very well by certain GLSL compilers.

Reviewed-by: Gunnar Sletta

2 files changed, 20 insertions, 4 deletions

diff --git a/src/gui/effects/qgraphicseffect.cpp b/src/gui/effects/qgraphicseffect.cpp
index 9ed003c..3a6bab5 100644
--- a/src/gui/effects/qgraphicseffect.cpp
+++ b/src/gui/effects/qgraphicseffect.cpp
@@ -101,6 +101,7 @@
 
 #include <QtGui/qimage.h>
 #include <QtGui/qpainter.h>
+#include <QtGui/qpaintengine.h>
 #include <QtCore/qrect.h>
 #include <QtCore/qdebug.h>
 #include <private/qdrawhelper_p.h>
@@ -260,12 +261,13 @@ QPixmap QGraphicsEffectSource::pixmap(Qt::CoordinateSystem system, QPoint *offse
     }
 
     QPixmap pm;
-    if (d->m_cachedSystem == system)
+    if (d->m_cachedSystem == system && d->m_cachedMode == mode)
         QPixmapCache::find(d->m_cacheKey, &pm);
 
     if (pm.isNull()) {
         pm = d->pixmap(system, &d->m_cachedOffset, mode);
         d->m_cachedSystem = system;
+        d->m_cachedMode = mode;
 
         d->invalidateCache();
         d->m_cacheKey = QPixmapCache::insert(pm);
@@ -708,9 +710,13 @@ void QGraphicsBlurEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
         return;
     }
 
+    QGraphicsEffectSource::PixmapPadMode mode = QGraphicsEffectSource::ExpandToEffectRectPadMode;
+    if (painter->paintEngine()->type() == QPaintEngine::OpenGL2)
+        mode = QGraphicsEffectSource::ExpandToTransparentBorderPadMode;
+
     // Draw pixmap in device coordinates to avoid pixmap scaling.
     QPoint offset;
-    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
+    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset, mode);
     QTransform restoreTransform = painter->worldTransform();
     painter->setWorldTransform(QTransform());
     d->filter->draw(painter, offset, pixmap);
@@ -893,9 +899,13 @@ void QGraphicsDropShadowEffect::draw(QPainter *painter, QGraphicsEffectSource *s
         return;
     }
 
+    QGraphicsEffectSource::PixmapPadMode mode = QGraphicsEffectSource::ExpandToEffectRectPadMode;
+    if (painter->paintEngine()->type() == QPaintEngine::OpenGL2)
+        mode = QGraphicsEffectSource::ExpandToTransparentBorderPadMode;
+
     // Draw pixmap in device coordinates to avoid pixmap scaling.
     QPoint offset;
-    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
+    const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset, mode);
     QTransform restoreTransform = painter->worldTransform();
     painter->setWorldTransform(QTransform());
     d->filter->draw(painter, offset, pixmap);
diff --git a/src/gui/effects/qgraphicseffect_p.h b/src/gui/effects/qgraphicseffect_p.h
index dff84a1..1ed7103 100644
--- a/src/gui/effects/qgraphicseffect_p.h
+++ b/src/gui/effects/qgraphicseffect_p.h
@@ -66,7 +66,12 @@ class QGraphicsEffectSourcePrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QGraphicsEffectSource)
 public:
-    QGraphicsEffectSourcePrivate() : QObjectPrivate() {}
+    QGraphicsEffectSourcePrivate()
+        : QObjectPrivate()
+        , m_cachedSystem(Qt::DeviceCoordinates)
+        , m_cachedMode(QGraphicsEffectSource::ExpandToTransparentBorderPadMode)
+    {}
+
     virtual ~QGraphicsEffectSourcePrivate() { invalidateCache(); }
     virtual void detach() = 0;
     virtual QRectF boundingRect(Qt::CoordinateSystem system) const = 0;
@@ -88,6 +93,7 @@ public:
 
 private:
     mutable Qt::CoordinateSystem m_cachedSystem;
+    mutable QGraphicsEffectSource::PixmapPadMode m_cachedMode;
     mutable QPoint m_cachedOffset;
     mutable QPixmapCache::Key m_cacheKey;
 };