Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!ncar!tank!uwvax!umn-d-ub!gandreas
From: gandreas@umn-d-ub.D.UMN.EDU (Glenn Andreas)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Odd scrollbar behavior with TrackControl
Message-ID: <536@umn-d-ub.D.UMN.EDU>
Date: 27 Oct 88 16:34:48 GMT
References: <942@ccnysci.UUCP> <13726@dhw68k.cts.com> <953@ccnysci.UUCP>
Reply-To: gandreas@ub.d.umn.edu.UUCP (Glenn Andreas)
Organization: University of Minnesota, Duluth
Lines: 50

In article <953@ccnysci.UUCP> alexis@ccnysci.UUCP (Alexis Rosen) writes:
>
>Ken McLeod recently responded to my original query (no, I'm not going to quote
>two pages.)
>
>Unfortunately, he erred in exactly the opposite direction that I did. I first
>said, "I'm using an ActionProc, and its arguments are sometimes garbage." Ken
>responds "Declare you arguments explicitly." That's exactly what I was doing,
>and that's why I was crashing.
>
>In fact, ActionProcs take EITHER two args (normal case) or none, for "dial
>indicators." That's one ugly interface. Yuck. (Wonder how NeXT does it ;-)
>
>----
>Alexis Rosen                       alexis@dasys1.UUCP  or  alexis@ccnysci.UUCP


How about just skipping the explicit tracking call all together?  I was a DA
recently that needed a scroll bar, so I though, no problem.  However, any
routine used as a ProcPtr needed to be scoped globallly (i.e., it can't be a
nested procedure, the static link throws everything off).  But, I needed to
get some information that was with the DA, and thus passed to the main
routine.  But you can't use global variables with DA's, so there was no easy
way to get information between the ActionProc and the main routine (well,
you could probably use the control's RefCon, but I said easy).  So what I
did was do my own TrackControl, and the whole thing looked clearer than
using TrackControl with and ActionProc.  Basically, I did the following:

	Get the part hit in the control.
	if the part hit = inThumb then
		TrackControl with no Action Proc
	else while part first hit = where the mouse now is and still down do
		case part hit of
		up : Scroll down one
		down : Scroll up one
		pageUp : Scroll down one page
		pageDown : Scroll up one page

Or something to this effect (I don't have the code nearby to be able to
quote).  The scroll routine took the amount and then updated the control by
that amount, checking min & max, etc - basically I did the work of
TrackControl, and if I get around to this, I will code this up as a simple
procedure that I can reuse.  This can go with my SetDialogItemValue and
GetDialogItemValue routines that I use all the time.  These could be good
candidates for the code sample library that was once talked about here.

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= "Whether you like it, or don't like it, sit   | - gandreas@ub.d.umn.edu - =
=  back and take a look at it, because it's the |   Glenn Andreas           =
=  best going today!  WOOOOoooo!" - Ric Flair   |                           =
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