Some things about backgrounds i never knew

[David Bovill]

I thought things were fairly simple - a background is a group with the
background behavior set to true, well at least as long as it is a toplevel
group and not a nested group - this definition works with the way that "the
backgroundids of stack" works.

The thing that throws me is that - what you really want to know is if a
group is the same object - that is if you change it's properties, colour
position etc - that these changes are reflected on other cards that share
this group. This equates to the groups having the same id = they are the
same object, and it turns out that this is not at all the same thing as the
definition above.

To test this all you need to do is create a group with "the
backgroundBehavior" set to true - create a few cards then turn "the
backgroundBehavior" off (set it to false). Now "the backgroundids of stack"
returns empty, but all the groups are the same id and therefore are and
behave as a background. It seems therefore that every toplevel group is a
potential background.

So the question is how do I find out what groups in a stack are in fact
backgrounds other than going through every card and checking the toplevel
ids of the groups to look for duplicates (and I guess "the backgroundids of
stack"). The LiveCode IDE's menu figures this out - but I guess only by
checking each card? Or is there a command to do this that I've missed?