Re: [AD] Triple Buffering under X?

[Evert Glebbeek <eglebbk@xxxxxxxxxx>]

On Saturday 04 September 2004 02:29, Chris wrote:
> I'm not sure if this is a good idea. For one, X doesn't even really do 
> page flipping (it just emulates it), so emulating a page flip method on 
> top of an emulated page flip is just heading for trouble.

Well, I'm not sure that's going to be much more trouble really. It's not 
really true triple buffering though; just page flipping with an unused 
video page.

> Plus, this 
> looks to be exactly why the retrace simulator was there in DOS (to 
> provide triple buffering when the driver wasn't capable), which was 
> recently deprecated.

Hmm... true. On the other hand, did that even work with X?

> I personally wouldn't even like X to do page flipping or allow for extra 
> "VRAM" access, although it seems that too many Allegro programs rely on 
> it and the X11 driver doesn't do a half-bad implementation of it.

I'm not sure how X handles this at all. I thought scrolling was a real 
possibility though? Or is that emulated as well?

> and the driver handles the rest. The only reason it wouldn't work is if 
> it's a buggy driver implementation. Besides, a quick look at the source 
> reveals that DGA2 can do triple buffering, so why not use that when 
testing?

Well, for one thing, it requires root access and if something screws up and 
the program hangs while in DGA 2 mode, I usually can't regain control of 
my computer except by doing a hard reset.
Not to mention the X11 driver actually is faster when using page flipping 
or triple buffering for me at the moment (~50 fps vs. ~4 fps). Not sure 
why that is though...

Evert