Mail Archives: djgpp/1997/04/12/10:23:50
Nick Bray writes:
> Well, I just got Allegro and I would have to say that it rules! Thanks
>Shawn! But I was a bit disturbed to learn that SVGA has no support for
>scrolling one pixel horizontally(?!). I wanted to use SVGA in my game but
>scrolling is very important and I think that four pixels at a time is just too
>jerky. Is there anything I can do about this? Any way around it?
I don't know of any workaround for this restriction: sorry! On some
cards you will be able to do pixel scrolling without any trouble (for
example with my native Tseng ET4000 driver, or using the Cirrus VESA
driver in my brother's PC). On others, which unfortunately seem to be
the majority, you will only be able to scroll in four pixel increments.
As far as I am aware this is a hardware restriction, because the display
start address only specifies a four-byte boundary and many SVGA chipsets
don't support the VGA pelpan registers, so there isn't anything I can do
to work round it. Please, someone correct me if I am wrong here, I'd
love to make it work properly!
The only workaround I can see would be to use a 16 or 32 bit mode, which
would give you 2 or 1 pixel scrolling respectively, but a) they are much
slower, b) they require more video memory, and c) I haven't finished
implementing them in Allegro yet :-)
--
Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
Beauty is a French phonetic corruption of a short cloth neck ornament.
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