why pop-to-buffer has this ugly behavior?

[Klaus Berndl <klaus.berndl@sdm.de>]

This is the implementation of custom-create-buffer in GNU Emacs 21.3:

,----
| (defun custom-buffer-create (options &optional name description)
|   "Create a buffer containing OPTIONS.
| Optional NAME is the name of the buffer.
| OPTIONS should be an alist of the form ((SYMBOL WIDGET)...), where
| SYMBOL is a customization option, and WIDGET is a widget for editing
| that option."
|   (unless name (setq name "*Customization*"))
|   (kill-buffer (get-buffer-create name))
|   (pop-to-buffer (get-buffer-create name))
|   (custom-buffer-create-internal options description))
`----

I have wondered why here pop-to-buffer does not split the unsplitted window in
my frame. Then i have tested the following (The value of `pop-up-windows' is
t!): 

(pop-to-buffer (get-buffer-create "*BlaBlaBla*"))

which splits an unsplitted window in 2 windows - well!

(pop-to-buffer (get-buffer-create "*Customization*"))

which does not split an unsplitted windows in 2 - very bad and ugly!

Conclusion: pop-up-buffer must have somewhere in the c-code - or maybe
display-buffer) but anyway - some logic which decides dependent on the
buffer-name if the window should be splitted or not?! I write this not to the
bug-list because it is not really a bug but it is a strong violation of one
of the most important design-principles: "Separation of concerns".

It is not the job of pop-to-buffer to decide on the buffer-name when to split
but it is the job of libraries like cus-edit.el to decide this.

Ugly things like that makes it sometimes really hard to develop
elisp-libraries like ECB.

Ciao,
Klaus

P.S.

BTW: here is how XEmacs implements custom-create-buffer - IMO the right way:

(defun custom-buffer-create (options &optional name description)
  "Create a buffer containing OPTIONS.
Optional NAME is the name of the buffer.
OPTIONS should be an alist of the form ((SYMBOL WIDGET)...), where
SYMBOL is a customization option, and WIDGET is a widget for editing
that option."
  (unless name (setq name "*Customization*"))
  (kill-buffer (get-buffer-create name))
  (switch-to-buffer (get-buffer-create name))
  (custom-buffer-create-internal options description))




-- 
Klaus Berndl			mailto: klaus.berndl@sdm.de
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