Use pixel events for smooth zooming

ui/pageview.cpp

@@ -3347,17 +3347,11 @@ void PageView::wheelEvent( QWheelEvent *e )
         vScroll = verticalScrollBar()->value();
     e->accept();
     if ( (e->modifiers() & Qt::ControlModifier) == Qt::ControlModifier ) {
-        d->controlWheelAccumulatedDelta += delta;
-        if ( d->controlWheelAccumulatedDelta <= -QWheelEvent::DefaultDeltasPerStep )
-        {
-            slotZoomOut();
-            d->controlWheelAccumulatedDelta = 0;
-        }
-        else if ( d->controlWheelAccumulatedDelta >= QWheelEvent::DefaultDeltasPerStep )
-        {
-            slotZoomIn();
-            d->controlWheelAccumulatedDelta = 0;
-        }
+        d->zoomFactor *= exp( (double)delta / 120.0 );
+        d->blockPixmapsRequest = true;
+        updateZoom( ZoomRefreshCurrent );
+        d->blockPixmapsRequest = false;
+        viewport()->repaint();
     }
     else
     {