Optimized blur / drop shadow effects for the GL 2 paint engine.

Do the blur in half the resolution in software and then upload the
result as a texture and smooth-scale it on the GPU. This leads to stable
and decent performance regardless of the blur radius, and simplifies the
implementation quite a bit.

Reviewed-by: Bjørn Erik Nilsen

1 files changed, 4 insertions, 7 deletions

diff --git a/src/gui/effects/qgraphicseffect.cpp b/src/gui/effects/qgraphicseffect.cpp
index dafea52..a523bab 100644
--- a/src/gui/effects/qgraphicseffect.cpp
+++ b/src/gui/effects/qgraphicseffect.cpp
@@ -844,22 +844,19 @@ QRectF QGraphicsBlurEffect::boundingRectFor(const QRectF &rect) const
 void QGraphicsBlurEffect::draw(QPainter *painter)
 {
     Q_D(QGraphicsBlurEffect);
-    if (d->filter->radius() <= 0) {
+    if (d->filter->radius() < 1) {
         drawSource(painter);
         return;
     }
 
     PixmapPadMode mode = PadToEffectiveBoundingRect;
     if (painter->paintEngine()->type() == QPaintEngine::OpenGL2)
-        mode = PadToTransparentBorder;
+        mode = NoPad;
 
     // Draw pixmap in device coordinates to avoid pixmap scaling.
     QPoint offset;
-    const QPixmap pixmap = sourcePixmap(Qt::DeviceCoordinates, &offset, mode);
-    QTransform restoreTransform = painter->worldTransform();
-    painter->setWorldTransform(QTransform());
+    QPixmap pixmap = sourcePixmap(Qt::LogicalCoordinates, &offset, mode);
     d->filter->draw(painter, offset, pixmap);
-    painter->setWorldTransform(restoreTransform);
 }
 
 /*!
@@ -1040,7 +1037,7 @@ void QGraphicsDropShadowEffect::draw(QPainter *painter)
 
     PixmapPadMode mode = PadToEffectiveBoundingRect;
     if (painter->paintEngine()->type() == QPaintEngine::OpenGL2)
-        mode = PadToTransparentBorder;
+        mode = NoPad;
 
     // Draw pixmap in device coordinates to avoid pixmap scaling.
     QPoint offset;