Re: pseudo transparency

[Sasha Vasko <sasha aftercode net>]

On Friday 11 January 2002 17:56, Owen Taylor wrote:
> >
> > Iportant problem here is that you leave shared resource unprotected
> > and unmanaged. Its as if you allowed client apps to set current
> > colormap as they like.
> >
> > Colormaps are actually another part of this particular issue, since it
> > would be desirous for clients to obtain the colormap/visual with which
> > such root pixmap was rendered.
>
> This is indeed somewhat of an issue. I don't think it's really worth
> the complexity of a whole new protocol, since even negotiating this
> doesn't provide a nice user interface to the user. Making sure
> that the background is set by only one app is the responsibility
> of the person configuring the desktop.

Like that we can blame anything at all on the user.
I could compile you nice big stack of bugreports and support requests related 
to this specific issue, since ESETROOT method is rather prone to 
misconfiguration. Don't forget also that applications tend to have bugs, and 
letting them play with such an important resource, that is used by many 
others, is not a good idea.

The problem is that you have shared resource at hand, and like anything else 
it has to be managed by window manager. And ICCCM compliant/recommended way 
of doing it is to use selection. Not that I'm inventing a wheel here.

> >  > >>Now one problem with the E method is that it may need
> > >>
> > >>a lot of memory (this depends on the memory you have and
> > >
> > > It takes _no_ extra memory. The pixmap is already referenced
> > > by the server, all the E method does is keep around a XID pointing
> > > to the pixmap.
> >
> > Not exactly correct. When you do XSetWindowBackgroundPixmap, what
> > server does is it creates a protected copy of the pixmap. X protocol
> > does not have clear requirement for this, but I'm yet to find a server
> > that does not do that. So you normally use twice as much memory as
> > needed with above approach.
>
> Making a copy wouldn't even be conformant to the X protocol. I can
> set the pixmap, change the pixmap, and subsequent exposes will
> reflect the change. I invite you to read the XFree86 sources and
> see if you can find the copy.

Alright! My prayers has been answered! Yooohoo.
It was not like this prior to XF 4.* thou
Still even memory usage is not a determining factor here. The main issue is 
resource management, and it is not a good idea to let clients to play with 
resource they don't own.


> Regards,
>                                         Owen

Sasha.