Re: [AD] al_convert_bitmap

[Peter Wang <novalazy@xxxxxxxxxx>]

On 2011-06-15, Elias Pschernig <elias.pschernig@xxxxxxxxxx> wrote:
> On Wed, Jun 15, 2011 at 2:54 AM, Matthew Leverton <meffer@xxxxxxxxxx> wrote:
> > On Tue, Jun 14, 2011 at 3:29 PM, Elias Pschernig
> > <elias.pschernig@xxxxxxxxxx> wrote:
> >> Makes sense. So al_destroy_display simply would go through the display
> >> bitmaps and remove the VIDEO flag from any bitmaps without the ANY flag
> >> - meaning the only operation allowed on them from now on is calling
> >> al_destroy_bitmap.
> >>
> > I took it to mean it would destroy the video bitmap and replace it
> > with something like a 1x1 memory bitmap. Thus the bitmap and all
> > operations on it would be valid, but there would be little memory
> > associated with it. To the programmer it would look like the bitmap
> > was simply "erased".
> >
> > It's really kind of a no-good-solution situation. I was trying to
> > avoid this altogether with the ANY_BITMAP approach.
> >
> > It was much simpler ... with it there's no difference between a video
> > bitmap and a memory bitmap that has been converted to a video bitmap.
> > Allegro wouldn't be able to tell them apart... they would always be
> > downgraded to memory and added back to the convert-list vector.
> >
> 
> So maybe we should leave it that way - if someone does not want it
> they can destroy all bitmaps before destroying the display. Even when
> converting to a 1x1 memory bitmap the zombie bitmaps still would use
> up memory and need to be destroyed, so the user must keep a list of
> the bitmaps either way.

They should be 0x0 bitmaps without any data associated.

We should allow al_create_bitmap to create 0x0 bitmaps anyway
(if we don't already).

> >> We could provide bitflags instead of numbers:
> >>
> >> NO_AUTO_MEM_VID = 1
> >> NO_AUTO_VID_MEM = 2
> >> NO_TRANSFER = 4
> >>
> > Mine were based on a bitfield, but I didn't have the transfer flag.
> > Given that the person could use al_convert_bitmaps() to transfer those
> > bitmaps, I don't think it's necessary.
> >
> > I wouldn't ever expect Allegro to transfer video bitmaps to another
> > dislpay... if it is doing it now, I wouldn't have thought it would.
> >
> 
> Yes, someone must have implemented that at some point, at least I see
> it for the OSX and X11 display drivers. The problem is when you have
> two displays and draw your bitmaps to both. As long as the OpenGL
> contexts are compatible that works. The bitmaps still are only in the
> list of one display though. When one is destroyed they are
> transferred.
> 
> Maybe we should not have a display option for al_destroy_display after
> all (as Trent said I guess). Then:
> 
> - Display destruction works like now (video bitmaps are transferred to
> anyother display if there is a compatible one, else converted to
> memory bitmaps).
> 
> - If you do not want this, simply destroy all your display bitmaps
> before destroying the display. (This would be slightly easier if we
> had that bitmap tagging system since user code would not need a list
> at all.)
> 
> The only values for the new display option then would be 0
> (AUTO_CONVERT bitmaps are converted in al_create_display) and 1
> (AUTO_CONVERT bitmaps are ignored).

I don't care for auto-conversion anyway so I'm still hoping you will
remove it from al_create_display and retract
al_convert_all_video_bitmaps...

Peter