From:	sorry AT too DOT dangerous (Fly Boy)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: 2 graphics questions
Date:	Tue, 11 Feb 1997 19:36:16 GMT
Lines:	26
Message-ID:	<3300b67e.2979457@news.telepac.pt>
References:	<01bc0fa6$3d6be440$5357f8ce AT 698130> <5d6cpv$b2o AT waldorf DOT csc DOT calpoly DOT edu>
NNTP-Posting-Host:	alm2_p2.telepac.pt
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

On 4 Feb 1997 04:09:35 GMT, jlouwere AT galaxy DOT csc DOT calpoly DOT edu (Jan
Louwerens) wrote:

>Ian Mausolus (mausolus AT ican DOT net) wrote:
>: What is that vertical retrace stuff all about?  Do you actaully have to
>: check to see if the video card or monitor is finished drawing to the screen
>: before displaying another picture?  and how do you do that?
>
>You don't have to wait for vertical retrace, but it could make your 
>animations look smoother by avoiding shearing.Her is how it's done:
>
>#include <pc.h>
>
>#define RetracePort 0x03DA
>
>void WaitVertRetrace(void)
>{
>   while(inportb(RetracePort) & 0x08);    // wait for end if already in VR
>   while(!(inportb(RetracePort) & 0x08)); // wait for VR to start...
>                                          // this way you get the entire VR
>}
>
>JL
>
Is there any way to have the vertical retrace generate a hardware
interrupt, so that you do not burn CPU cycles away waiting for it ?

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