Fix scroll speed with hand tool when zoomed in/out

src/board/UBBoardController.cpp

@@ -920,7 +920,8 @@ void UBBoardController::zoom(const qreal ratio, QPointF scenePoint)
 
 void UBBoardController::handScroll(qreal dx, qreal dy)
 {
-    mControlView->translate(dx, dy);
+    qreal antiScaleRatio = 1/(mSystemScaleFactor * currentZoom());
+    mControlView->translate(dx*antiScaleRatio, dy*antiScaleRatio);
 
     UBApplication::applicationController->adjustDisplayView();