window configurations no longer (since 21.5) include windows ! ?

[Michael Sperber]

"Stephen J. Turnbull" <stephen at xemacs.org> writes:

> Michael Sperber writes:
>
>  > While this wasn't exactly intentional, identity preservation was a
>  > kludge with the old implementation that tied down a number of internal
>  > invariants related to GC we wanted to get rid of.
>
> Where is this documented?  To the best of my knowledge the window
> configuration refactoring just plopped down on XEmacs Patches one day
> with no design documentation, and I don't recall ever hearing that it
> was related to GC.  I always thought it was about moving to modern
> pixel-based dimensions and getting non-performance-critical code out
> of C.

There were several factors.  The initial motivation was GC.  However,
there were comments (by Ben, I believe) in the code saying that it
should be rewritten in Elisp.  (The old code also used pixel-based
dimensions.)

The thing about identity preservation pops up first here:

http://osdir.com/ml/emacs.xemacs.patches/2002-11/msg00099.html

(I.e. before I even committed the rewrite.)

> I guess you missed this passage from the XEmacs Lisp manual:
>
>     38.3 Deleting Windows
>     =====================
>
>     A window remains visible on its frame unless you "delete" it by
>     calling certain functions that delete windows.  A deleted window
>     cannot appear on the screen, but continues to exist as a Lisp
>     object until there are no references to it.  There is no way to
>     cancel the deletion of a window aside from restoring a saved
>     window configuration (*note Window Configurations::).  Restoring a
>     window configuration also deletes any windows that aren't part of
>     that configuration.
>
> The section on window configurations is pretty careful to avoid
> mentioning window identities, but it doesn't explicitly deny that IDs
> will be preserved.

Sure.  Even the new code *sometimes* preserves them.

> Also, anybody with expertise in X11 (and maybe Windwoes and
> Carbon/Cocoa) would assume that windows can be withdrawn and restored
> without losing their identities.

Without support from the explicit documentation, I would argue that
those assumptions were always unsafe.

-- 
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla