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

4 files changed, 26 insertions, 14 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;
 };
diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index 7d9390c..738c6e3 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -10703,7 +10703,8 @@ QPixmap QGraphicsItemEffectSourcePrivate::pixmap(Qt::CoordinateSystem system, QP
     if (mode == QGraphicsEffectSource::ExpandToEffectRectPadMode) {
         effectRect = item->graphicsEffect()->boundingRectFor(sourceRect).toAlignedRect();
     } else if (mode == QGraphicsEffectSource::ExpandToTransparentBorderPadMode) {
-        effectRect = sourceRect.adjusted(-1, -1, 1, 1).toAlignedRect();
+        // adjust by 1.5 to account for cosmetic pens
+        effectRect = sourceRect.adjusted(-1.5, -1.5, 1.5, 1.5).toAlignedRect();
     } else {
         effectRect = sourceRect.toAlignedRect();
     }
diff --git a/src/gui/image/qpixmapfilter.cpp b/src/gui/image/qpixmapfilter.cpp
index f9ac79f..d0de03e 100644
--- a/src/gui/image/qpixmapfilter.cpp
+++ b/src/gui/image/qpixmapfilter.cpp
@@ -584,7 +584,7 @@ Qt::RenderHint QPixmapBlurFilter::blurHint() const
 QRectF QPixmapBlurFilter::boundingRectFor(const QRectF &rect) const
 {
     Q_D(const QPixmapBlurFilter);
-    const qreal delta = d->radius * 2;
+    const qreal delta = d->radius + 1;
     return rect.adjusted(-delta, -delta, delta, delta);
 }
 
@@ -1057,14 +1057,9 @@ void QPixmapDropShadowFilter::setOffset(const QPointF &offset)
 QRectF QPixmapDropShadowFilter::boundingRectFor(const QRectF &rect) const
 {
     Q_D(const QPixmapDropShadowFilter);
-
-    const qreal delta = qreal(d->radius * 2);
-    qreal x1 = qMin(rect.left(), rect.left() + d->offset.x() - delta);
-    qreal y1 = qMin(rect.top(), rect.top() + d->offset.y() - delta);
-    qreal x2 = qMax(rect.right(), rect.right() + d->offset.x() + delta);
-    qreal y2 = qMax(rect.bottom(), rect.bottom() + d->offset.y() + delta);
-
-    return QRectF(x1, y1, x2 - x1, y2 - y1);
+    qreal delta = d->radius + 1;
+    return rect.adjusted(-2, -2, 2, 2).united(
+            rect.translated(d->offset).adjusted(-delta, -delta, delta, delta));
 }
 
 /*!