Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!pdn!xanadu!reese
From: reese@xanadu.nm.paradyne.com (Don Reese)
Newsgroups: comp.os.minix
Subject: Re: MOUSE SYSTEM
Keywords: Description of my  mouse system
Message-ID: <6824@pdn.paradyne.com>
Date: 11 Dec 89 13:41:55 GMT
References: <2675@gos.ukc.ac.uk>
Sender: usenet@pdn.paradyne.com
Reply-To: reese@xanadu.paradyne.com (Don Reese)
Organization: AT&T Paradyne, Largo, Florida
Lines: 42

In article <2675@gos.ukc.ac.uk> tkb1@ukc.ac.uk (Tor Kristjan Berge) writes:
>
>Basic description:
>When the mouse driver detects a change in  the  status  of  the  mouse
>driver  (ie. the mouse has moved or a button is pressed / released), a
>signal is sent to the application program. The application program now
>reads the mouse driver and updates the internal data of the mouse.  If
>neccesary, the mouse cursor is moved. 
>

I am not a minix programmer, though I have been a Unix programmer (since rel 3
on a PDP11/34), I have also spent a good bit of time writing code for
MS/Dos and X Windows systems.  I have been reading this news group on an
off since it became available and should personal time become available,
would like to put minix on my personal machine (AT Compatable) at home.
But I am a little concerned over the use of signals to indicate mouse
events.  Exactly what will be considered a mouse event.  Any movement of
the mouse?  This could generate an event for each pixel the mouse is moved
(if the mickey/pixel ratio is set to one both hirizontally and vertically).
Why not set up the mouse driver to store all information about the current
mouse state in a simple structure.  Then provide a read/write interface
that allows the user to set the control part of the structure via a write
and access the current mouse information with a read.  Use the mouse driver to
keep track of the current state of the mouse, then let the application program
worry about how often the mouse status is read.

How will access to the mouse driver by multiple programs be controlled?.
Since Minix is a multitasking environment, you will either have to limit the
driver to supporting a single open (returning a busy state to the second open)
or must provide some knowlege of window geometries within the mouse driver
(probably better to use single open and let the window geometry code belong
to a windowing system).

Where will the drawing of the mouse icon be handled?  In MS/Dos, the mouse
driver is responsible for the drawing and moving of the mouse icon.  In this
way the mouse icon provides for smooth mouse movement, even when the
application can not keep up with the flow of mouse information.
--
Don Reese              reese@pdn.paradyne.com    | Eney Meeny, Jelly Beanie,
AT&T Paradyne          {mtdca, uunet}!pdn!reese  | the spirits are about to
P.O. Box 2826          Mail Stop LG-133          | speak. - Bullwinkle Moose
Largo, FL  34649-2826  Phone: (813) 530-8361