Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!dimacs.rutgers.edu!rutgers!cbmvax!peter
From: peter@cbmvax.commodore.com (Peter Cherna)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: How to do a "MovePointer()"?
Message-ID: <22627@cbmvax.commodore.com>
Date: 21 Jun 91 15:58:36 GMT
References: <19997@csli.Stanford.EDU> <caw.2099@miroc.Chi.IL.US>
Reply-To: peter@cbmvax.commodore.com (Peter Cherna)
Organization: Commodore-Amiga, Inc.  West Chester, PA.
Lines: 53

In article <caw.2099@miroc.Chi.IL.US> caw@miroc.Chi.IL.US (Christopher A. Wichura) writes:
>In article <19997@csli.Stanford.EDU> bratt@csli.Stanford.EDU (Harry Bratt) writes:
>>I need to change the position of Intuition's mouse pointer.  I
>
>>Currently I'm doing:
>>
>>IntuitionBase->MouseX = x;
>>IntuitionBase->MouseY = y;
>>SetPointer(...);
>>
>>This appears to work....  but...

That is illegal.
>
>The above looks kinda illegal to me.  What you might consider is doing
>something like this:
>
>	lock = LockIBase(0);
>	CurX = IntuitionBase->MouseX;
>	CurY = IntuitionBase->MouseY;
>	<calculate delta to where you want the mouse to be>
>	<create an input event and send it to input.device>
>	UnlockIBase(lock);

I don't think I'd do a DoIO() to input.device while inside LockIBase().
In any case, you can't guarantee that there aren't other input events
(from the hardware) moving the mouse.  All you want to do is get
an atomic reading of MouseX and MouseY.  That is to say, if the
mouse-coords change from (100,50) to (120,40) at one time, you
want to avoid reading (100,40) or (120,50).  Since MouseX and
MouseY are both words, you can grab them in one shot:

sturct MouseCoords
{
    WORD MouseY;
    WORD MouseX;
} mouse;

	(* (ULONG *)(&mouse)) = (* (ULONG *)(&IntuitionBase->MouseY) )
	/* set-up event and perform DoIO() */

That horrible expression basically reads:  pretend there is a ULONG
value starting at IntuitionBase->MouseY, and copy it into the ULONG
we're pretending is located at 'mouse'.

>Christopher A. Wichura                Multitasking.  Just DO it.

     Peter
--
Peter Cherna, Operating Systems Development Group, Commodore-Amiga, Inc.
{uunet|rutgers}!cbmvax!peter    peter@cbmvax.commodore.com
My opinions do not necessarily represent the opinions of my employer.
"Gosh, didn't he have anything positive to say at all?"