net@TUB.BITNET (Oliver Laumann) (12/11/88)
I don't understand the rationale behind the functions XtCallbackNone, XtCallbackNonexclusive, XtCallbackExclusive, and XtCallbackPopdown. Why are they called `callback' functions and why would one want to use these functions instead of XtPopup and XtPopdown? Usually, `callback functions' are provided by an application programmer and called by the code implementing a widget. The above mentioned functions, however, are exported by the Toolkit. Should they be put into a callback list, and if so, into which one? Regards, -- Oliver Laumann net@TUB.BITNET net@tub.UUCP
asente@decwrl.dec.com (Paul Asente) (12/14/88)
In article <8812111548.AA07300@tub.UUCP> net@TUB.BITNET (Oliver Laumann) writes: >I don't understand the rationale behind the functions XtCallbackNone, >XtCallbackNonexclusive, XtCallbackExclusive, and XtCallbackPopdown. >Why are they called `callback' functions and why would one want to use >these functions instead of XtPopup and XtPopdown? > >Usually, `callback functions' are provided by an application programmer >and called by the code implementing a widget. The above mentioned >functions, however, are exported by the Toolkit. Should they be put >into a callback list, and if so, into which one? These are just convenience functions for the programmer. If all your callback routine needs to do is call XtPopup or XtPopdown, you can put XtCallback{None, Nonexclusive, Exclusive, Popdown} in the callback list and avoid having to write the function. -paul asente asente@decwrl.dec.com decwrl!asente