Re: [AD] DGA driver improvement

[Shawn Hargreaves <shawn@xxxxxxxxxx>]

Eric Botcazou <botcazou@xxxxxxxxxx> writes:
> I've tried to improve the linux DGA driver, more precisely the
> interaction between the windowed modes and the window manager:
> Allegro will ask the user to choose the window location before entering
> the DGA windowed mode.

Is this really how it ought to work, though? Since the DGA mode disables 
other apps while it is active, what is the point of being able to control 
the exact placement on your desktop? It really behaves like a fullscreen 
mode with regard to other apps, so it's almost just a fluke that when you 
don't use the mode changing version, it may not cover your entire screen.

At one point someone suggested that maybe the DGA window should be 
centered on your desktop in these situations, and should black out the 
border areas, which seems logical to me.

Another thing to consider is what happens when you do page flipping, or 
use offscreen video memory. At the moment this works ok in fullscreen DGA 
mode, but when you do it in windowed DGA mode, you can see the supposedly 
'hidden' pages flickering across other parts of the display. Michael 
pointed out that this can be useful for debugging, which is very true, 
but it is also quite disturbing when you are trying to play a game :-)
It's hard to see how this could be made to work, though, as every video 
bitmap would need a suitable black border if we wanted to prevent 
anything else from being visible.

I guess the question is whether non-fullscreen DGA mode is intended to be 
useful for actual games, or just for development, and if the former, how 
exactly should it work? Comments would be appreciated...

On a related note, does anyone know how other DGA games (eg. the Loki 
stuff) behave? Do they always switch to the desired fullscreen video 
mode, or do they have options to use DGA in a window?



-- 
Shawn Hargreaves - shawn@xxxxxxxxxx - http://www.talula.demon.co.uk/
"A binary is barely software: it's more like hardware on a floppy disk."