Cheers, please send us a the test stack!
As far as I can see though from all your detailed comments there is no such
thing as a background script that can be shared by a number of scripts a
card level (at control level yes), but there is no script layer between the
card and the stack.
For most situations this is not a problem, as most scripts are called from
controls. I just happened to have a stack where I used the card script - and
voila no background scripts get intercepted!
Thanks.
> From: "Raymond E. Griffith" <[EMAIL PROTECTED]>
> Reply-To: [EMAIL PROTECTED]
> Date: Fri, 21 Jul 2000 09:00:56 -0400
> To: [EMAIL PROTECTED]
> Subject: Re: There is no background script: card script come first...
>
> on 7/21/2000 6:11 AM, David Bovill <[EMAIL PROTECTED]> wrote:
>>
>> Starting to use groups and they are definitely a major advance, but I guess
>> I have to change the architecture of my stack for testing scripts, which
>> used to rely on card script passes to background script hierarchy.
>>
> Here are some scenarios for the message hierarchy. There are some *very*
> definite differences in how these things behave, depending upon the origin
> of the call.
>
> Control on a Card (Button, etc)
> The Card
> Group 4 (highest layered group)
> Group 3
> Group 2
> Group 1 (lowest layered group)
> Stack
>
> A script on a Card
> Group 4 (highest layered group)
> Group 3
> Group 2
> Group 1 (lowest layered group)
> Stack
>
> A button in group 2
> Group 2
> The Card
> Stack
>
>> Now with Metacard we have Stacks - cards - groups? So the only way for a
>> script on a card to have access to shared scripts is to place them at stack
>> level, or perhaps do something unorthodox with the message hierarchy.
>
> No, shared scripts can be done with groups.
>
>> Inserting would seem to allow me to effectively place scripts before the
>> target/card or after the "home" scripts???
>
> Insert into Front places the script of the object inserted into prominence
> before anything else. Suppose you have a handler "on doittoit" in your
> button, and a handler "on doittoit" in the object whose script is set to the
> front. Your button's call to "doittoit" will not go the the button's script
> first, but to the front script!
>
> So you should only put items in the front that you would never want to
> intercept in an object.
>
> Insert into Back places the script of the object inserted into place after
> the stack's script. Any handler in a back script can be intercepted by
> blocking the message hierarchy with a handler of the same name.
>>
>> The "Objects" card of the "Concepts & Techniques" stack seems to indicate
>> that messages pass through along:
>>
>> control - group - card - background - stack
>>
> It depends. See the above examples. I set up a situation in which I had
> several controls which would "pass" a handler after receiving it, and would
> record the object that received it. That is how I figured this out.
>
>> Since as far as I can tell a group is identical to a background except for
>> how it is referred to then I am unclear when a groups/backgrounds script
>> will be called?
>>
>> Does it depend whether the group is on the card??? If it is not will it
>> still be intercepted as a background object (as suggested by "Objects" card
>> of the "Concepts & Techniques")?
>>
> A group not on a card does not sit in the hierarchy for that card.
>
>> I think the answer for my stack will be to set the script of an object on a
>> group in order to test it, rather than setting the card script. Suppose I'm
>> just trying to pin down the concept of "backgrounds" in MetaCard and the
>> implications for property inheritance and message passing.
>>
>> How's this for a definition:
>>
>> 1) a group is a background placed on a card
>> 2) all groups are therefore in this sense backgrounds
>> 2b) or alternatively a background is a group not on the current card.
>> 3) stacks can contain backgrounds which are not placed on any cards
>> 4) backgrounds do not receive messages, only when placed on a card as a
>> group.
>> 5) try to forget about backgrounds and think of groups and layers
>>
> I see where you are going here. I'm not sure all of this is technically
> correct, but it is a start.
>
> I have a one-page stack with the message hierarchy test on it. If you want
> it, send a request off list.
>
> Cheers,
>
> Raymond
>
>
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