Make it possible to implement engine-specific drop shadow filters

It wasn't possible for the paint engine to override the drop
shadow filter because QPixmapDropShadowFilter::draw() was not
asking for an engine-specific filter object.

Also, change the OpenVG filter to use vgGaussianBlur() instead of
vgConvolve(), and draw the original image on top of the shadow.

Task-number: QTBUG-4583
Reviewed-by: trustme

1 files changed, 10 insertions, 0 deletions

diff --git a/src/gui/image/qpixmapfilter.cpp b/src/gui/image/qpixmapfilter.cpp
index 749b8f3c11..df445db53a 100644
--- a/src/gui/image/qpixmapfilter.cpp
+++ b/src/gui/image/qpixmapfilter.cpp
@@ -1074,6 +1074,16 @@ void QPixmapDropShadowFilter::draw(QPainter *p,
                                    const QRectF &src) const
 {
     Q_D(const QPixmapDropShadowFilter);
+    QPixmapFilter *filter = p->paintEngine() && p->paintEngine()->isExtended() ?
+        static_cast<QPaintEngineEx *>(p->paintEngine())->pixmapFilter(type(), this) : 0;
+    QPixmapDropShadowFilter *dropShadowFilter = static_cast<QPixmapDropShadowFilter*>(filter);
+    if (dropShadowFilter) {
+        dropShadowFilter->setColor(d->color);
+        dropShadowFilter->setBlurRadius(d->blurFilter->radius());
+        dropShadowFilter->setOffset(d->offset);
+        dropShadowFilter->draw(p, pos, px, src);
+        return;
+    }
 
     QImage tmp = src.isNull() ? px.toImage() : px.copy(src.toRect()).toImage();
     QPainter tmpPainter(&tmp);