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From: vishniac@wanginst.UUCP (Ephraim Vishniac)
Newsgroups: net.micro.mac
Subject: Re: Is My Thumb an Indicator?
Message-ID: <1318@wanginst.UUCP>
Date: Tue, 12-Nov-85 15:44:39 EST
Article-I.D.: wanginst.1318
Posted: Tue Nov 12 15:44:39 1985
Date-Received: Wed, 13-Nov-85 04:01:34 EST
References: <1283@wanginst.UUCP>
Distribution: net
Organization: Wang Institute, Tyngsboro, Ma.  01879
Lines: 28

> According to the Control Manager chapter of IM, the action proc for
> a particular control will be called repeatedly as long as the mouse is
> down in some part of the control.  True enough, it will.  It also says
> that there are two flavors of action procs, depending on whether or not
> the control is an "indicator".  If it is, the action proc is a parameterless
> procedure (no arguments, no return value).  If not, the action proc
> receives the control handle and part code as arguments.  IM points out
> that it's important to know what kind of control you're dealing with,
> since "obviously" your action proc can only be of one type or the other.
> 
> My problem: when I mouse down in the scrolling or paging regions of my
> scrollbar, my action proc is called exactly as advertised with the
> appropriate handle and part code on the stack.  When I mouse down in the
> thumb (the little square item that shows the scroll bar position), my
> action proc is called without parms as though the thumb were an indicator!

Since writing this, I've found that the Control Manager chapter does mention
that the thumb of a scroll bar is, generically speaking, the "indicator" of
a "dial."  This still fails to explain, though, why my actionProc is called
with varying argument lists and how one is expected to deal with this.  So,
I repeat my original question:

> Has anyone run into this curiosity?  Has anyone used a scrollbar action
> proc and *not* run into this?
-- 
Ephraim Vishniac
  [apollo, bbncca, cadmus, decvax, harvard, linus, masscomp]!wanginst!vishniac
  vishniac%Wang-Inst@Csnet-Relay