From:	"Damian Yerrick" <web DOT poison AT pineight DOT 8m DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Allegro datafile load command positioning
Date:	Sun, 3 Oct 1999 00:25:56 -0500
Organization:	Rose-Hulman Institute of Technology
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Stefan Viljoen <rylan AT intekom DOT com> wrote in message
news:7t33md$mnj$3 AT ctb-nnrp2 DOT saix DOT net...
> Hi!
>
> Encountered a nice little messy tick today - it seems that if you use the
> VESA1 driver in set_gfx_mode for Allegro, and use the 640x480x16 bit color
> depth, and want to use RLE sprites, DO NOT load the datafile before
> attempting to set the gfx mode! What I did was
>
> allegro_init();
> install_*();
> foo = load_datafile("foo.dat");
> Then I attempt to display an RLE sprite in the DATAFILE - causes
> crash of whole system (95 goes down too) with no traceback

Are you trying to draw the RLE sprite to the text screen? Maybe
that's it. RLE sprites are designed to be drawn to graphics screens.

> It works however if you load the datafile AFTER the call to set_gfx_mode -
>
> Why?!

Setting the graphics mode tells Allegro how to convert RLE sprites
to the format that the video card expects. Before set_gfx_mode(),
the system is in 8-bit color mode.

> IMHO this does not make sense - you just load the datafile,
> that's all it is - data - what does the setting or not of the gfx mode
> have to with it all?

load_datafile() also reformats the bitmaps to the card's favorite
pixel format.

> It very definitely crashes on my system if I load the datafile before
> setting the mode, and then try to display the RLE sprite after setting gfx
> mode. If I set mode however, and then load the file, it works fine.

Hope this helps!


Damian Yerrick
http://come.to/yerrick

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