bug#18337: 24.4.50; apropos fails on "scroll"

[Detlev Zundel <dzu@akk.org>]

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Hi,

> Hi Stefan,
>
> [added Dmitry on CC as the changelog seems to make a connection to the
> problem at hand]
>
>>> (when (setq properties (symbol-plist 'vertical-scroll-bar))
>>>   (setq doc (list (car properties)))
>>>   (while (setq properties (cdr (cdr properties)))
>>>     (setq doc (cons (car properties) doc)))
>>>   (nreverse doc))
>>
>>> => (0 event-symbol-element-mask event-symbol-elements
>>> modifier-cache variable-documentation)
>>   
>>> Applying 'symbol-name to that list then yields the error.
>>
>> Note that, while convention is to use a symbol for property names, that
>> is not the only valid choice.  0 is a valid property name (tho an odd
>> one, arguably).
>
> I think in this case it actually caught an error though.
>
>> So while this 0 should probably be changed the mapconcat code that burps
>> on it should probably be changed not to assume that only symbols will
>> be used as property names.
>
> Looking deeper, it turns out that the 0 results from this:
>
> buffer.c:5473
>
>   DEFSYM (Qvertical_scroll_bar, "vertical-scroll-bar");
>   Fput (Qvertical_scroll_bar, Qchoice, list4 (Qnil, Qt, Qleft, Qright));
>   DEFSYM (Qhorizontal_scroll_bar, "horizontal-scroll-bar");
>
>   DEFSYM (Qfraction, "fraction");
>   Fput (Qfraction, Qrange, Fcons (make_float (0.0), make_float (1.0)));
>
>   DEFSYM (Qoverwrite_mode, "overwrite-mode");
>   Fput (Qoverwrite_mode, Qchoice,
> 	list3 (Qnil, intern ("overwrite-mode-textual"),
> 	       intern ("overwrite-mode-binary")));
>
> As far as I can tell, it should thus really be 'choice.  Actually both
> vertical-scroll-bar and overwrite-mode have the problem:
>
> (symbol-plist 'vertical-scroll-bar)
>
> => (0 (nil t left right) event-symbol-element-mask (vertical-scroll-bar 0) event-symbol-elements (vertical-scroll-bar) modifier-cache ((0 . vertical-scroll-bar)) variable-documentation 374228)
>
> (symbol-plist 'overwrite-mode)
>
> => (0 (nil overwrite-mode-textual overwrite-mode-binary) event-symbol-element-mask (overwrite-mode 0) event-symbol-elements (overwrite-mode) modifier-cache ((0 . overwrite-mode)) :minor-mode-function binary-overwrite-mode variable-documentation 370277)
>
> The changelog mentions this
>
> 2014-07-16  Dmitry Antipov  <dmantipov@yandex.ru>
>
> 	More precise control over values of some buffer-local variables.
> 	* keyboard.c (Qvertical_scroll_bar):
> 	* frame.c (Qleft, Qright): Move to ...
> 	* buffer.c (Qleft, Qright, Qvertical_scroll_bar): ... here.
> 	* buffer.c (Qchoice, Qrange, Qoverwrite_mode, Qfraction): New symbols.
> 	(syms_of_buffer): DEFSYM all of the above, attach special properties.
> 	Use special symbols to DEFVAR_PER_BUFFER overwrite-mode,
> 	vertical-scroll-bar, scroll-up-aggressively
> 	and scroll-down-aggressively.
>
> Dmitry, do you know why the construct for choice fails?

The attached patch fixes the problem for me as the plist now looks like
this:

(symbol-plist 'vertical-scroll-bar)
=> (choice (nil t left right) event-symbol-element-mask (vertical-scroll-bar 0) event-symbol-elements (vertical-scroll-bar) modifier-cache ((0 . vertical-scroll-bar)) variable-documentation 374812)

Cheers
  Detlev
  
-- 
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From 5294eb80883abc3fb06805f972693664b294079f Mon Sep 17 00:00:00 2001
From: Detlev Zundel <dzu@member.fsf.org>
Date: Thu, 11 Sep 2014 10:37:54 +0200
Subject: [PATCH] * src/buffer.c (syms_of_buffer): Add forgotten Qchoice DEFSYM

---
 src/ChangeLog | 4 ++++
 src/buffer.c  | 1 +
 2 files changed, 5 insertions(+)

diff --git a/src/ChangeLog b/src/ChangeLog
index e20072d..393fbe7 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2014-09-11  Detlev Zundel  <dzu@member.fsf.org>
+
+	* buffer.c (syms_of_buffer): Add forgotten Qchoice DEFSYM
+
 2014-09-03  Martin Rudalics  <rudalics@gmx.at>
 
 	* buffer.c (scroll-bar-height): Fix typo in doc-string.
diff --git a/src/buffer.c b/src/buffer.c
index 45e614f..dd1e205 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -5386,6 +5386,7 @@ syms_of_buffer (void)
   staticpro (&Qpermanent_local);
   staticpro (&Qkill_buffer_hook);
 
+  DEFSYM (Qchoice, "choice");
   DEFSYM (Qleft, "left");
   DEFSYM (Qright, "right");
   DEFSYM (Qrange, "range");
-- 
2.1.0