Scale canvas with mouse anchor

resources/ui/carla_host.ui

@@ -136,7 +136,11 @@
          <number>1</number>
         </property>
         <item row="0" column="1">
-         <widget class="DraggableGraphicsView" name="graphicsView"/>
+         <widget class="DraggableGraphicsView" name="graphicsView">
+          <property name="transformationAnchor">
+           <enum>QGraphicsView::AnchorUnderMouse</enum>
+          </property>
+         </widget>
         </item>
         <item row="0" column="2">
          <widget class="DigitalPeakMeter" name="peak_out" native="true"/>