Re: [AD] per-thread transformation and blending mode

[Peter Wang <novalazy@xxxxxxxxxx>]

Peter Hull: sorry, it was on A.cc:
    http://www.allegro.cc/forums/thread/604400/871602#target

On 2010-06-24, Elias Pschernig <elias.pschernig@xxxxxxxxxx> wrote:
> On Thu, 2010-06-24 at 13:59 -0400, Pavel Sountsov wrote:
> > 
> > On 06/24/2010 09:49 AM, Peter Wang wrote:
> > >
> > > If you replace the "current display" with the "currently targetted
> > > display" (i.e. the display that owns the target bitmap), this scheme
> > > leads to confusing behaviour.  When you target a video bitmap, you take
> > > the transformation/blending from the target display.  But when you
> > > target a memory bitmap, there is no target display, so the
> > > transformation/blending has to be taken from thread-local state.
> 
> Another idea would be to keep it per-target-bitmap. For example if you
> use transformations to make the coordinate system go from 0,0 to 1,1 for
> the whole backbuffer it would be annoying if you have to reset it each
> time you switch back from drawing to another bitmap.

Good idea.  Each bitmap has its own clipping rectangle, and I think
transformations go along with that.

I *think* I would prefer the blending mode to be per-thread, though.

> > Do you have any plans for deferred drawing also? It's the other 
> > display-local feature other than transformations and blending.
> > 
> 
> I think changing the target bitmap while deferred drawing is on should
> not be permitted.

I agree.

Peter