Re: Re: FW: XFree86 future

Am Sonntag, 23. März 2003 23:31 schrieb Havoc Pennington:
> On Sun, Mar 23, 2003 at 09:32:09PM +0100, Lukas Molzberger wrote:
> > Sure, you also have to do synchronization in a direct rendering model but
> > it's a whole lot easier if you don't have to take care of the network
> > protocol.
>
> Why would it be?
>
> > If there is no network protocol then you don't need to keep backward
> > compatibility of the network protocol.
>
> Without a network protocol your interface is the ABI of your shared
> library, and you have to keep backward compatibility of *that* - which
> is at least as hard if not harder than keeping the network protocol.
>
> > If the only possibility to keep backward compatibility is to add
> > new extensions to the core protocol then many problems will be solved in
> > a hackish way which leads to complexity and therefore also to other
> > problems.
>
> Same is true of an ABI.
>
> > The issue of backward compatibility also exists in the X11 API's but it's
> > a far smaller problem to break bw compatibility of an API then it is to
> > break the compatibility of a network protocol. Imagine the functionality
> > that has been added from GTK 1.2 to GTK 2.0 would have been added just by
> > extensions.
>
> 2.0 is one big extension to 1.2. We keep 1.2 around installing in
> parallel; see http://ometer.com/parallel.html
Yes, but each of them is a complete and clean API. No application will ever 
use both of them at the same time. I guess that almost all developers are 
using 2.0 by now. It might be that most functionality is added in form of new 
functions but I'm sure there were also a lot of modifications and cleanups to 
functions that were already present in 1.2. However, these modifications and 
cleanups are not possible in X11 API. If you have a problem in some part of 
the X11 API you can either replace that part with a new extension or you can 
come up with a hack. Most of the time people came up with hacks. That's why 
there are still so many functions in use that are more than 10 years old. But 
adding extensions is also more difficult than in the Gtk case. In Gtk either 
new functions are used or the old functions. In X11 a program can use either 
the new functions or the old functions or any mixture of them.    
I guess that in one or two years Gtk 1.2 will be gone for good, but people 
will still have to come up with hacks for issues in more that 10 year old X11 
API functions.
I think the compatibility breakage between Gtk 1.2 and Gtk 2.0 was no big deal 
for the enduser. The same would be true if a new Version X11 API would be 
released. The only thing that would really break would be the X11 protocol.
  
>
> With a network protocol, we keep the old and new parts of the
> protocol. It's the same thing, and equally complicated.  In both
> cases, if everyone stops using the old thing someday, you could
> theoretically delete it, but chances are you never get to delete it in
> practice.
>
> > Another problem of the X11 protocol is that events that an application
> > wants to send have to be compressed by the application to get a decent
> > performance. Correct me if I'm wrong, but as far as I have understood it,
> > the only reason why this is necessary is the network protocol.
>
> I think I'd need more specifics to know what you mean here.
>
> > > We also do have a reasonably OK-looking hack in metacity/GTK that uses
> > > the SYNC extension to ensure that we do 1 frame repaint, 1 client
> > > repaint, 1 frame repaint, 1 client repaint, alternating, instead of
> > > what happens now where sometimes you redo the frame 30 times and
> > > repaint the client only once. (The GTK patch for this hasn't been
> > > applied, so there's no way to try this yourself yet.)
> >
> > That sounds nice! Will this work accross both desktops, Gnome and
> > Kde?
>
> It would if we standardized it, right now it's in the metacity namespace.
> People on wm-spec-list didn't seem interested in standardizing it.
>
> Havoc
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