Re: [AD] 4.3 display update methods

["Robert Ohannessian" <ROhannessian@xxxxxxxxxx>]

Why can't Allegro implement the dirty rectangle part?

> -----Original Message-----
> From: alleg-developers-bounces@xxxxxxxxxx [mailto:alleg-
> developers-bounces@xxxxxxxxxx] On Behalf Of Chris
> Sent: Monday, July 24, 2006 5:00 PM
> To: Coordination of admins/developers of the game programming library
> Allegro
> Subject: Re: [AD] 4.3 display update methods
> 
> On Monday 24 July 2006 14:39, Peter Hull wrote:
> > The thing is, there's nothing AFAICS in OpenGL (or D3D) that
> > guarantees that your front buffer is always retained*.
> 
> No, but if you're drawing to the back buffer, you'll clear it up with
the
> next
> update. If you're drawing to the front buffer, you'd be using a
> dirty-rectangle-like system (or otherwise could have your own buffer),
and
> would check for display update events to clear it up. There's no dire
need
> to
> keep a copy of the front buffer.
> 
> > However, there may be performance issues. For example, on my
(slightly
> > old) iBook, requesting a retained OpenGL context is incompatible
with
> > the hardware renderer. In D3D there is an indication you can get
> > better performance by telling it that the backbuffer need not be
> > preserved.
> 
> I mean, preserve the front buffer for when the system wants to make it
> 'dirty'
> for whatever reason.
> 
> > Thinking about our target audience, the choice they should be
thinking
> > about is "Do I want to handle redraws myself or let Allegro do it?",
> > not "Do I want to implement a dirty rectangle system on a front
buffer
> > or use the back buffer"
> 
> The two are rather synonymous.
> Handle redraws yourself - dirty rectangles - draw to front
buffer/screen
> Allegro handles redraws - buffered drawing - draw to back buffer and
flip
> 
>
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