From:	gautam AT interlog DOT com (Gautam N. Lad)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Problem with XOR (Allegro)
Date:	Mon, 27 Oct 97 16:03:37 GMT
Organization:	InterLog Internet Services
Lines:	37
Message-ID:	<632dgn$o5m$2@news.interlog.com>
NNTP-Posting-Host:	ip213-65.cc.interlog.com
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hi,
Ok, I've a palette in a Datafile, which I load up when my program runs.  The 
colours are defined so I don't have to use numbers.   Like so:

#define YELLOW	5
#define WHITE	4
#define XOR_ON	xor_mode(-1);
#define XOR_OFF	xor_mode(0);

circle(screen, 100, 200, 5, YELLOW);

Now, I have a problem.  It seems that when I turn XOR enabled, the colours 
value seem a bit differnet.  What I mean is, if I draw using YELLOW, the colour 
WHITE (index in palette of 4 in my case) get's used.  Is this how XOR 
works?  I'm pretty sure, but I don't think it should change the colour I'm drawing 
with.  Now, this is on a background colour (index value of 0 in palette), with 
nothing on it.  It seems the colour being used is one less then what I want.

I do something like this:

XOR_ON;
	circle(screen, 100, 200, 5, YELLOW);
XOR_OFF;

The result is a WHITE circle.

Any ideas?
Bye!

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Gautam N. Lad
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E-Mail:	gautam AT interlog DOT com
Website:	http://www.interlog.com/~gautam

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