# Modeless Operation

> [HTML Version](modelessoperation_1.htm)

In addition to the additional programming required (multiple XCALL XTREE operations using different XTR\_OPCODE values), these present the problem of how to respond to the user clicking on the list box when some other input field has the input focus (i.e. when not inside of an XCALL XTREE operation). You can prevent this problem by disabling the control on exit (see flags XTF\_DISABLE) or you can define a keyboard click-to-enable string in XTR\_KBDSTR, which would be received by whatever input routine had the focus at the time the user clicked on the tree control. This would allow your application logic to take appropriate action, presumably including executing a new XCALL XTREE operation. If you neither disable the pick list when inactive, nor define a click-to-enable string in XTR\_KBDSTR, then the user may have the impression of operating on the control, but your program will not be aware of it. (It could, however, retrieve the current selection(s) at some later time by executing XCALL XTREE with XTR\_OPCODE set to 4 and _flags_ set to include XTF\_NOSEL, which would have the effect of simply returning the current selection information.)

The recommended sequence for XTR\_KBDSTR is chr(7)+chr(250)+###. (where ### is the desired _EXITCODE_ number to be returned from the INFLD call which receives the sequence.) For example, to return _EXITCODE_ 175 to INFLD when the user clicks on the pick list (while an INFLD operation is active), set XTR\_KBDSTR=chr(7)+chr(250)+"175." (Note the trailing period.)