Date:	Thu, 3 Jun 93 10:56:52 CST
From:	(csaba AT vuse DOT vanderbilt DOT edu) <csaba AT vuse DOT vanderbilt DOT edu>
To:	hegt AT iaci DOT kun DOT nl
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu
Subject:	Re: fast memory to VGA update

On Thu, 03 Jun 93 08:20:58 CDT,
  <hegt AT iaci DOT kun DOT nl> writes:

>
>Hello all,
>
>I am currently porting an application to the PC using DJGPP. Everything
>works remarably smooth, but I have this little qusetion involving the
>graphics part of my port.
>
>The application I am working on is some kind of windowing system, which
>does maintain a memory mapped 2 bits deep bitmap of the image that is to
>be displayed on the screen. I have already prototyped a solution where I
>have replaced my own graphical primitives by LIBGRX primitives, and that
>works quite alright. Because it is very likely that I am going to have
>to port more of this type of applications, which are using the same
>memory bitmap scheme but different primitives I would rather like a
>blazingly fast way to update the PC screen from this 640x400x2 bitmap.
>
>Since I am only supporting the standard VGA mode, I suppose the can be a
>faster way than using the standard libgrx calls, which are portable
>between several drivers and modes.
>
>Does anyone have any hints on where to look or how to go on?
>
>Thanks,
>Rob Hegt

You could change the standard GRX bitblt code to transfer only two planes 
instead of four. The 16 color planar VGA version of this routine is in 
'p4bitblt.c'. 

Csaba

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