Revert "MainRootWindow.qml: remove unused viewSwitch() function"

This reverts commit 9a8acc6c1a.

src/ui/MainRootWindow.qml

@@ -126,6 +126,22 @@ ApplicationWindow {
         return _rgPreventViewSwitch[_rgPreventViewSwitch.length - 1]
     }
 
+    function viewSwitch(currentToolbar) {
+        toolDrawer.visible      = false
+        toolDrawer.toolSource   = ""
+        flightView.visible      = false
+        planView.visible        = false
+        toolbar.currentToolbar  = currentToolbar
+    }
+
+    function showFlyView() {
+        if (!flightView.visible) {
+            mainWindow.showPreFlightChecklistIfNeeded()
+        }
+        viewSwitch(toolbar.flyViewToolbar)
+        flightView.visible = true
+    }
+
     function showPlanView() {
         viewSwitch(toolbar.planViewToolbar)
         planView.visible = true