Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!harrier.ukc.ac.uk!elder.ukc.ac.uk!rlh2
From: rlh2@ukc.ac.uk (R.L.Hesketh)
Newsgroups: comp.windows.x
Subject: Re: Wcl conceptual trouble
Message-ID: <234@elder.ukc.ac.uk>
Date: 4 Feb 91 09:47:56 GMT
References: <jsparkes.665548362@bwdls49>
Reply-To: rlh2@ukc.ac.uk (Richard Hesketh)
Organization: Computing Lab, University of Kent at Canterbury, UK.
Lines: 47

In article <jsparkes.665548362@bwdls49> jsparkes@bwdls49.bnr.ca (Jeff Sparkes) writes:
	
>	Wcl programming is done on a callback basis, right?  The problem is
>that an Xaw dialog has no callback.  What I really want to do is have a
>callback in the OK button which says "call callback X with the value of the
>text field".  It would probably be useful in some cases to specify the
>"src" widget for the callback.

If the OK button is a commandWidget then the callback is "callback".
Callbacks can be passed the name of a widget as a string argument:

	*loadDialog.okButton.callback: load_file(*loadDialog.value)

The load_file callback would be bound using:

	WcRegisterCallback(app, "load_file", load_file, NULL);

and when called the client_data is a string "*loadDialog.value".  This
can be converted into the the Widget id using:

void
load_file(w, client_data, call_data)
Widget w;
XtPointer client_data, call_data;
{
	Widget id = WcFullNameToWidget(w, (char *)client_data);

	...
}

>	This is more generally applicable too.  I have a list widget in
>which I select a field; then a command button is clicked which wants to call
>a callback with the value of the list widget.

Again you can pass the widget name as the client data.

What would be useful is a GetValues interface for Wc which already has
WcSetValuesCB() and WcSetValuesACT().  However to get an equivalent
WcGetValuesCB() which would return a string when used in something like:

	fred.callback: do_something(WcGetValuesCB(*valueEntry.value))

the addition of TypeToString converters would be required for all the different
application resource types.  This would also be very useful for UI Builders
etc but I fear we have missed the boat on this one.

Richard