[comp.sys.mac.hypercard] Layers

mesard@bbn.com (Wayne Mesard) (05/09/89)

In article <12877@ut-emx.UUCP> newman@emx.UUCP (David Newman) writes:
>What this thread seems to imply to me is that we need a way to inherit
>material from other backgrounds.  I too have a stack with several similar
>backgrounds, and the ideal thing would be to create one bg with all the 
>common elements, and inherit those features in the other backgrounds.

Why not generalize it a bit more:  Make a "Card" a collection of layers,
where each layer has the property of a having a layer underneath it.
Think of it as a pile of transparancies.  What we call the card layer
now is the first layer pointed to by the Card object in the new scheme.
The background layer becomes the bottommost layer on the pile (i.e. the
last layer in the card's layer list.)  This allows things like

   set bg of this card ...

which we were discussing at the start of this thread and ...

>
>I know this would be tough in HyperCard, and terribly incompatible with
>earlier releases.

it would be completely compatible with earlier releases ;-)


-- 
void *Wayne_Mesard();         Mesard@BBN.COM         BBN, Cambridge, MA