Constructs an editor reactor object that notifies of a change to a system variable

(vlr-sysvar-reactor data callbacks)



Any AutoLISP data to be associated with the reactor object; otherwise nil if no data.


A list of pairs of the following form:

(event-name . callback_function)

where event-name is one of the symbols listed in the “SysVar reactor events” table below, and callback_function is a symbol representing a function to be called when the event fires. Each callback function accepts two arguments:

reactor_object The VLR object that called the callback function.

list A list of extra data elements associated with the particular event. The contents of this list for particular events are shown in the “SysVar reactor callback data” table.

Return Values

The reactor_object argument.

SysVar reactor events

Event name



AutoCAD is about to change the value of a system variable.


The value of a system variable has changed.

SysVar reactor callback data


List length




A string identifying the system variable name.



First parameter is a string identifying the system variable name.

Second parameter is symbol indicating whether the change was successful (T if successful, nil if not).