Re: [AD] al_update_display_region

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On Thu February 26 2009, Elias Pschernig wrote:
> On Thu, 2009-02-26 at 17:02 +0200, Milan Mimica wrote:
> > I see. That works too, but I was thinking something more than that.
> > Our official position is: the contents of the backbuffer are undefined
> > after al_flip_display(). OK, that works, you render the whole
> > backbuffer and try to save some resources by indicating the rectangle
> > that has changed since the last frame. It will either flip, or update
> > the whole buffer area, or update only the specified region, or
> > transfer data through space shuttle...
> >
> > I was thinking we could bend the rules a bit, since we also have
> > ALLEGRO_SWAP_METHOD display option which would allow you to choose a
> > buffer copy update method. Then you could render to the backbuffer
> > only the portion of the screen that has changed and update only that
> > region(s). How evil is that?
> > I should also mention that currently no driver supports both
> > ALLEGRO_SWAP_METHOD and al_update_display_region() in a reliable way
> >
> > :)
>
> The question is, how reliably can D3D/WGL/GLX/OSX-GL drivers tell us
> about the swap method? Also, would it require any changes? As far as I
> can see, a swap method of COPY means you can treat the display as if it
> were a single buffer (and the behavior of al_update_display_region in
> current SVN then should be correct).

The question is, what will be needed for a software (X11, GDI+) driver if and 
when its implemented?

> Also, while I updated the docs for the new display options, I was
> thinking ALLEGRO_DOUBLEBUFFERED is named wrong, as it is also used for
> page flipping/triple buffering/undefined method. Maybe we should rename
> it to ALLEGRO_SINGLEBUFFER (with reversed meaning of course) and remove
> the display flag of the same name.
>
> --
> Elias Pschernig <elias@xxxxxxxxxx>
>
>
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-- 
Thomas Fjellstrom
tfjellstrom@xxxxxxxxxx




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