Specifies whether or not map layers in the group are potentially visible.
For the map layer to actually be visible on the map, this property and the layer's visibility property must be true, and the current view must be within the visible scale range defined for the group.
This property adheres to the setAutoRefresh method except when called from the onViewChanging or onViewChanged events.
Note that this property is not available during a busy state. For additional information about the busy state, see "Handling Busy State and Map Refresh" in the Autodesk MapGuide Developer's Guide.