DDLightbarMenu OnItemNav on initial display

DDLightbarMenu can now optionally call its OnItemNav function when
it's first displayed.  By default this behavior is disabled, but it
can be enabled by setting the (new) callOnItemNavOnStartup property
to true.

exec/load/dd_lightbar_menu.js

@@ -291,7 +291,12 @@ lbMenu.exitOnItemSelect = false;
 OnItemNav is a function that is called when the user navigates to a new item (i.e., via
 the up or down arrow, PageUp, PageDown, Home, End, etc.).  Its parameters are the old
 item index and the new item index.
-this.OnItemNav = function(pOldItemIdx, pNewItemIdx) { }
+lbMenu.OnItemNav = function(pOldItemIdx, pNewItemIdx) { }
+
+To have the menu object call OnItemNav() when it is first displayed to get the user's
+choice, set the callOnItemNavOnStartup property to true:
+lbMenu.callOnItemNavOnStartup = true;
+By default, it is false.
 
 The 'key down' behavior can be called explicitly, if needed, by calling the DoKeyDown() function.
 It takes 2 parameters: An object of selected item indexes (as passed to GetVal()) and, optionally,
@@ -474,6 +479,10 @@ function DDLightbarMenu(pX, pY, pWidth, pHeight)
 	this.inputTimeoutMS = 300000; // Input timeout in ms
 	this.mouseEnabled = false;
 
+	// Whether or not to call OnItemNav() when the menu is first displayed
+	// to get the user's choice
+	this.callOnItemNavOnStartup = false;
+
 	// Member functions
 	this.Add = DDLightbarMenu_Add;
 	this.Remove = DDLightbarMenu_Remove;
@@ -1389,6 +1398,9 @@ function DDLightbarMenu_GetVal(pDraw, pSelectedItemIndexes)
 			this.DisplayInitialScrollbar(this.scrollbarInfo.solidBlockLastStartRow);
 	}
 
+	if (this.callOnItemNavOnStartup && typeof(this.OnItemNav) === "function")
+		this.OnItemNav(0, this.selectedItemIdx);
+
 	// User input loop
 	var userChoices = null; // For multi-select mode
 	var selectedItemIndexes = { }; // For multi-select mode