[TD]use QGraphicsView anchor for zoom

src/Mod/TechDraw/Gui/QGVNavStyle.cpp

@@ -287,13 +287,9 @@ void QGVNavStyle::handleWheelEvent(QWheelEvent *event)
 
 void QGVNavStyle::zoom(double factor)
 {
-    QPoint center = getViewer()->viewport()->rect().center();
+    setAnchor();
     getViewer()->scale(factor,
                        factor);
-
-    QPoint newCenter = getViewer()->viewport()->rect().center();
-    QPoint change = newCenter - center;
-    getViewer()->translate(change.x(), change.y());
     m_zoomPending = false;
 }
 

src/Mod/TechDraw/Gui/QGVNavStyleTouchpad.cpp

@@ -47,14 +47,12 @@ void QGVNavStyleTouchpad::handleKeyPressEvent(QKeyEvent *event)
 {
 //    Q_UNUSED(event)
     if (event->key() == Qt::Key_PageUp) {
-        setAnchor();
         zoom(1.0 + zoomStep);
         event->accept();
         return;
     }
 
     if (event->key() == Qt::Key_PageDown) {
-        setAnchor();
         zoom(1.0 - zoomStep);
         event->accept();
         return;
@@ -101,7 +99,6 @@ void QGVNavStyleTouchpad::handleMouseMoveEvent(QMouseEvent *event)
         QGuiApplication::keyboardModifiers().testFlag(Qt::ShiftModifier) ) {
         //if control and shift are down, then we are zooming
         if (zoomingActive) {
-            setAnchor();
             zoom(mouseZoomFactor(event->pos()));
         } else {
             startZoom(event->pos());