Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!ames!ucbcad!ucbvax!ucdavis!egg-id!ui3!wsucshp!kinner
From: kinner@wsucshp.UUCP (Bill Kinnersley )
Newsgroups: comp.sys.amiga
Subject: Who is Intuition?  What is she?
Message-ID: <160007@wsucshp.UUCP>
Date: Mon, 18-May-87 17:51:34 EDT
Article-I.D.: wsucshp.160007
Posted: Mon May 18 17:51:34 1987
Date-Received: Sat, 23-May-87 11:24:20 EDT
Organization: WSU Computer Science
Lines: 55



(I'm running about two months late..this has been a busy
semester)

In article <2679@well.UUCP> ewhac@well.uucp (Leo 'Bols Ewhac'
Schwab) writes:

  [in a discussion of messages and replies thereto]

> 	For the sake of completeness, Intuition is a totally
> different animal.  Intuition is not an I/O driver, it's a sort
> of application.  You don't send requests (messages) to
> Intuition, Intuition sends messages to YOU.  That's why, when
> you get an IntuiMessage, you should reply to it as soon as you
> can..

	It's a different animal, I'll grant you that, but it's not
even "sort of" an application.  The way I understand it,
Intuition is a library.  Nothing more.

	It is made to have the appearance of an independent task,
but only because it is called at such frequent intervals by other
system tasks.  Mostly by the input.device, which calls the entry
point Intuition() and supplies a stream of input events. 
Intuition() turns some of these into IntuiMessages.

	Messages and ports are designed to handle communications
between two exec tasks.  Intuition appears to act as a task when
it sends you a message to your IDCMP UserPort and you have to
send it a reply, but that's a fake--it's all done with mirrors.  

	Take a look at the contents of an IntuiMessage.  The Reply
Port for the Message is the other IDCMP port in your Window,
w->WindowPort.  But the SigTask is NULL, and the Flag is IGNORE. 
There *is* no Intuition task listening on the other end, and your
faithful replies to Intuition are just being enqueued. 
Presumably Intuition() has to scoot around and poll all these
ports itself as part of its own housekeeping.

	In fact, Intuition implemented as a task would quickly run
into problems.  In the first place, someone would surely be
tempted to RemTask() it.  Secondly, since there is a limit of 16
signals available to each task, there can only be allocated 16
different Message Ports at once, hence Intuition (if it were a
task) could manage only 16 windows.

---
"Nesting is for the birds"
                --Bill Kinnersley
    USENET: ...!ucbvax!ucdavis!egg-id!ui3!wsucshp!kinner
    INTERNET: kinner%wsu@RELAY.CS.NET
    CSNET: kinner@wsu
    MAIL: CS Dept, Washington State Univ, Pullman WA 99164-1210
    PHONE: (509)332-3340