Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!chad
From: chad@csd4.csd.uwm.edu (D. Chadwick Gibbons)
Newsgroups: comp.lang.pascal
Subject: Re: Reading the keyboard
Keywords: keyboard scancodes
Message-ID: <3950@csd4.csd.uwm.edu>
Date: 23 Aug 89 03:28:40 GMT
References: <835@eutrc3.urc.tue.nl>
Sender: news@csd4.csd.uwm.edu
Reply-To: chad@csd4.csd.uwm.edu (D. Chadwick Gibbons)
Followup-To: comp.lang.pascal
Distribution: usa
Organization: University of Wisconsin-Milwaukee
Lines: 42

In article <835@eutrc3.urc.tue.nl> p.v.bemmelen writes:
|the user should be able to press multiple keys, and the program should
|detect all of them, not just the last one pressed.

	To have this work properly, the main loop of your program needs to be
a keyboard scanning routine.  This can be done very easily in Turbo Pascal,
accomplished with a routine such as:
	
	FUNCTION InKey : CHAR;
	BEGIN
	  Port[$60] := $00; { set "no delay" repeat }
	  WHILE NOT (KeyPressed) DO
	    ;
	  InKey := ReadKey
	END;

This is all you need.  Repeats will be handled as expected: upon they next
call, they are still in the buffer, and will be able to read immediately read
from this function.

	A few things to note: setting the repeat delay above may not work on 
XT class machines.  I don't have access to an XT, but I have seen this used in
one of Borland's OOP demonstration programs included with version 5.5 of TP.
You'll have to experiment to determine if this is a portable usage.  It makes
no real difference to the program, but a faster repeat is indispensable, in my
opinion.  Note too that ReadKey returns zero if an extended key has been
pressed.  If you're using InKey as an expression in the case, check for zero
and read the buffer again, i.e.:

	ch := InKey;
	CASE ch OF
	  0: ch := ReadKey; { get extended key }
	  ...
	  ...
	END;

	Keyboard reading is easily accomplished using Turbo's own built in
function and really does not require any external interference unless you are
preforming actions based upon control keys being pressed (i.e. if ALT is
touched, the status line may display another set of functions, etc, etc.)
--
D. Chadwick Gibbons (chad@csd4.csd.uwm.edu)