When is message passing required?

dunbarx at aol.com dunbarx at aol.com
Mon May 23 12:09:57 EDT 2016

I think the question is being asked "backwards".

If you trap a message, it will die in that handler unless passed explicitly. This is simple to understand  for the"mousdUp" message, say, because that is trapped for a specific reason, and may or may not be passed, as required. 

But with "keyDown", the action taken also disrupts what most would consider an automatic engine action, apart, perhaps, from any specific additional user action. So the "automatic" action will not take place unless the message is passed, and this lack of function trips up new users.

But there is no intrinsic difference, only that the expectations of the user are different.

Craig Newman

-----Original Message-----
From: J. Landman Gay <jacque at hyperactivesw.com>
To: How to use LiveCode <use-livecode at lists.runrev.com>
Sent: Mon, May 23, 2016 11:31 am
Subject: Re: When is message passing required?

On May 23, 2016 8:15:52 AM Paul Dupuis <paul at researchware.com> wrote:

> Does anyone have a compiled list of which messages need to be passed or
> *should* be passed vs those that you do not have to concern yourself with?

There's no real rule about it, it all depends on the stack and it's own set 
of handlers. In some cases you want the message passed so that another 
handler can continue to process the message, and in other cases you don't 
want to do that because further processing isn't wanted or needed. And if 
there aren't any other handlers in the message path that process the 
message then it doesn't matter if you pass it or not.

Jacqueline Landman Gay         |     jacque at hyperactivesw.com
HyperActive Software           |     http://www.hyperactivesw.com

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