Re: ddraw: Improve GetScanLine stub so it's usable for timing related tasks

[Christian Costa]

Le 06/04/2012 12:35, Piotr Caban a écrit :
> - /* Simulate a 60Hz display */
> - time = GetTickCount();
> - frame_progress = time&  15; /* time % (1000 / 60) */
> - if (!frame_progress)
> - {
> -
>    *Scanline = 0;
> -
>    return DDERR_VERTICALBLANKINPROGRESS;
> - }
> -
> - /* convert frame_progress to estimated scan line */
> - lines = mode.height / 15;
> - *Scanline = (frame_progress - 1) * lines + time % lines;
>  return DD_OK;
> }

Is time % lines here is to generate a random values (sort of noise) ?

ddraw: Improve GetScanLine stub so it's usable for timing related tasks

[Piotr Caban]

On 04/06/12 13:33, Christian Costa wrote:
> Le 06/04/2012 12:35, Piotr Caban a écrit :
> > - /* Simulate a 60Hz display */
> > - time = GetTickCount();
> > - frame_progress = time& 15; /* time % (1000 / 60) */
> > - if (!frame_progress)
> > - {
> > - *Scanline = 0;
> > - return DDERR_VERTICALBLANKINPROGRESS;
> > - }
> > -
> > - /* convert frame_progress to estimated scan line */
> > - lines = mode.height / 15;
> > - *Scanline = (frame_progress - 1) * lines + time % lines;
> >
> > return DD_OK;
> > }
>
> Is time % lines here is to generate a random values (sort of noise) ?

Yes. It's mainly there to make the function return more then 16 
different values. But it's not guarantying that all of the lines may be 
ever returned.

ddraw: Improve GetScanLine stub so it's usable for timing related tasks

[Christian Costa]

Le 06/04/2012 13:45, Piotr Caban a écrit :
> On 04/06/12 13:33, Christian Costa wrote:
> > Le 06/04/2012 12:35, Piotr Caban a écrit :
> > > - /* Simulate a 60Hz display */
> > > - time = GetTickCount();
> > > - frame_progress = time& 15; /* time % (1000 / 60) */
> > > - if (!frame_progress)
> > > - {
> > > - *Scanline = 0;
> > > - return DDERR_VERTICALBLANKINPROGRESS;
> > > - }
> > > -
> > > - /* convert frame_progress to estimated scan line */
> > > - lines = mode.height / 15;
> > > - *Scanline = (frame_progress - 1) * lines + time % lines;
> > >
> > > return DD_OK;
> > > }
> >
> > Is time % lines here is to generate a random values (sort of noise) ?
>
> Yes. It's mainly there to make the function return more then 16 
> different values. But it's not guarantying that all of the lines may 
> be ever returned.

Ok. Thanks. It might worth adding a comment for that tough.