Volume 6A: Motif Programming Manual

XmTextInsert() to add the dashes when appropriate. The problem with this approach is that XmTextInsert()

activates the XmNmodifyVerifyCallback function again, so the dash would be subject to the input filtering.

As a result, the only way to handle the situation is to actually add the dashes in the

XmN-modifyVerifyCallback routine at the same time the digits are added. This approach involves modifying

the ptr and length fields of the XmTextBlock structure in the XmTextVerifyCallbackStruct. The

check_phone() routine checks the current length of the phone number. If it is either two or six characters long, the

routine reallocates ptr to hold two characters, adds the dash, and increments length to account for the dash.

When the Text widget adds the digit and the dash, it positions the insertion cursor at the end of the new text. Prior to

Motif 1.2, the position of the insertion cursor was not affected by the amount of text that was added. The workaround

to this problem was to use the XmNvalueChangedCallback and call XmTextSetInsertionPosition().

Although we haven't demonstrated its use, the XmNvalueChangedCallback is useful when you need to keep

track of the changes in a Text widget, but you don't need to monitor or change the input before it is displayed. This

callback is invoked after the text has been modified in any way, which means that it is called for each insertion and

deletion. The call_data parameter to the routine is of type XmAnyCallbackStruct; the reason field is

always XmCR_VALUE_CHANGED ...