Path: utzoo!attcan!uunet!snorkelwacker!usc!brutus.cs.uiuc.edu!psuvax1!psuvm!dn5
From: DN5@psuvm.psu.edu
Newsgroups: comp.sys.mac.hypercard
Subject: Re: Backgrounds, sub (super backgrounds)
Message-ID: <90073.091704DN5@psuvm.psu.edu>
Date: 14 Mar 90 14:17:04 GMT
References: <16814@orstcs.CS.ORST.EDU> <285@gazette.bcm.tmc.edu>
 <287@gazette.bcm.tmc.edu>
Organization: Penn State University
Lines: 38


-    I have 100 cards all sharing the same
-    background (fields,buttons, icons,drawings) plus that 10 of these 100
-    cards also share in addition other things(buttons,fields, ..) between
-    these 10 cards.
-    is it possible to define one background in terms of another?
-    currently I only know how to define a background from scratch.
-    I mean, If I have a backgound that has a,b,c can I define another
-    that have a,b,c plus d,e,f (like a super set)?

The traditional way is to create a clean background, and then copy
over everything (don't forget any background graphics) into the
new background.

There is, however, a much easier way.  Copy a card (by choosing the
menu item).  Then make any change to the background (even 1 pixel
to the background graphics does it).  Then paste the card where you
want the new background.  By comparing background ids, you will
notice that the background for this new card has a different id
than the original background.  You can now go back to the original
card, and fix the background graphic (or whatever else you changed).

This works because when you copy a card (put it into the clipboard),
the complete information for that card includes a complete description
of the background -- in case you were to paste it into another stack.
When it is pasted back, it compares ids with any backgrounds in the
stack, and ONLY if the backgrounds are IDENTICAL (I assume by
checksum or somesuch device) will the id remain the same.  Otherwise
the pasted background is given a new id number, and assumed to be
a completely different background.

Simple, easy, and totally non-obvious.  There should have been
a better way of copying a background, or better yet, getting
rid of the background/card dicotomy, and having multiple levels
of background, each inheriting things from its ancestors.

                          D. Jay Newman
                          dn5@psuvm.psu.edu