Multiple values in widget?

[Lars Clausen <lrclause cs uiuc edu>]

In Dia, we have a very generic system for Properties dialogs that allows us
to set properties for several objects at the same time.  However, we're not
quite sure how to represent a value that is different in different objects.

Example:

A diagram has three lines, two of width 3, one of width 5.  The user
selects all lines and opens the properties dialog.  What should the line
width widget show?  Obviously, if the user changes it, it will be set to
the same for all three lines.  But there should be some indication that the
values aren't currently the same for all objects.

Other programs:  Abiword will blank out the selectors for fonts, but for
font style, it unselects the B/I/U selectors rather than indicate there's
differences.
Kword sets the selectors based on where you end the select-drag.
Kivio just picks one value (first object, I think) and shows that.
Visio marks one object in a different select color and that object's
values is shown in the dialog.

Are there any HIG people around who could give input on how it's best to
handle this kind of thing?  Ignore it?  Mark one object as 'master'?  Add
some decoration to imply that a value is not the same for all selected
objects? 

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| Hårdgrim of Numenor
"I do not agree with a word that you say, but I   |----------------------------
will defend to the death your right to say it."   | Where are we going, and
    --Evelyn Beatrice Hall paraphrasing Voltaire  | what's with the handbasket?