bug#4338: 23.1; truncate-partial-width-windows yields too small width

[Andrew Hyatt]

I just tested, and can confirm that this is still a problem in Emacs 25.

Eli Zaretskii <eliz@gnu.org> writes:

> Please write in English if possible, because the Emacs maintainers
> usually do not have translators to read other languages for them.
>
> Your bug report will be posted to the bug-gnu-emacs@gnu.org mailing list,
> and to the gnu.emacs.bug news group.
>
> Please describe exactly what actions triggered the bug
> and the precise symptoms of the bug:
>
>   emacs -Q
>   C-x 3
>   M-x set-variable RET truncate-partial-width-windows RET 30 RET
>
> Now type "C-x }" in the left window until the right window starts
> truncating its lines on the display.  When that happens, count the
> number of columns in the right window.  I get 25, whereas the expected
> value is 29, or at least 27, if someone wants to argue that the fringe
> counts.
>
> It may be that the width of the scroll bar counts as well, but in that
> case this should be reflected in the doc string.
>
> The above is in a GUI session.  On a TTY, I do get 29 characters, but
> only if I count the truncation glyph as well.
>
> If Emacs crashed, and you have the Emacs process in the gdb debugger,
> please include the output from the following gdb commands:
>     `bt full' and `xbacktrace'.
> If you would like to further debug the crash, please read the file
> d:/usr/emacs/etc/DEBUG for instructions.
>
>
> In GNU Emacs 23.1.1 (i386-mingw-nt5.1.2600)
>  of 2009-07-31 on HOME-C4E4A596F7
> Windowing system distributor `Microsoft Corp.', version 5.1.2600
> configured using `configure --with-gcc (3.4)'
>
> Important settings:
>   value of $LC_ALL: nil
>   value of $LC_COLLATE: nil
>   value of $LC_CTYPE: nil
>   value of $LC_MESSAGES: nil
>   value of $LC_MONETARY: nil
>   value of $LC_NUMERIC: nil
>   value of $LC_TIME: nil
>   value of $LANG: ENU
>   value of $XMODIFIERS: nil
>   locale-coding-system: cp1255
>   default-enable-multibyte-characters: t
>
> Major mode: Lisp Interaction
>
> Minor modes in effect:
>   tooltip-mode: t
>   tool-bar-mode: t
>   mouse-wheel-mode: t
>   menu-bar-mode: t
>   file-name-shadow-mode: t
>   global-font-lock-mode: t
>   font-lock-mode: t
>   blink-cursor-mode: t
>   global-auto-composition-mode: t
>   auto-composition-mode: t
>   auto-encryption-mode: t
>   auto-compression-mode: t
>   line-number-mode: t
>   transient-mark-mode: t
>
> Recent input:
> <help-echo> <help-echo> C-x 3 M-x s e t - v a r <tab> 
> <return> t r u n c a <tab> p <tab> <return> 3 0 <return> 
> <mouse-1> <mouse-1> <down-mouse-1> <drag-mouse-1> <help-echo> 
> <help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
> <down-mouse-1> <help-echo> <help-echo> <mouse-movement> 
> <help-echo> <help-echo> <mouse-movement> <help-echo> 
> <help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
> <help-echo> <mouse-movement> <help-echo> <help-echo> 
> <help-echo> <help-echo> <help-echo> <help-echo> <mouse-movement> 
> <help-echo> <help-echo> <mouse-movement> <help-echo> 
> <help-echo> <mouse-movement> <help-echo> <help-echo> 
> <mouse-movement> <help-echo> <help-echo> <mouse-movement> 
> <help-echo> <help-echo> <mouse-movement> <help-echo> 
> <help-echo> <mouse-movement> <help-echo> <help-echo> 
> <help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
> <mouse-movement> <help-echo> <help-echo> <mouse-movement> 
> <help-echo> <drag-mouse-1> <help-echo> <help-echo> 
> C-x o <up> <up> <up> <up> <right> <right> <right> <right> 
> <right> <right> <right> <right> <right> <right> <right> 
> <right> <right> <right> <right> <right> <right> <right> 
> <right> <right> <left> <left> <left> <left> <left> 
> <left> <left> <left> <left> C-x ^ <down> <up> <down> 
> C-x { C-x } C-x } <up> <up> <right> <right> <right> 
> <right> <right> <right> <right> <right> <right> <right> 
> <right> <right> <right> <right> <right> <right> <right> 
> <right> <right> <right> <right> <right> <right> <right> 
> <right> C-x } C-x { C-x { <left> <left> <left> <left> 
> <left> <left> <left> <left> <left> <left> <left> <left> 
> <left> <left> <left> <left> <left> <left> <left> <left> 
> <left> <left> <left> <left> <left> <help-echo> <help-echo> 
> <help-echo> <help-echo> <help-echo> C-x o C-x } C-x 
> { C-x { C-x } C-x { C-x 1 M-x r e p o r t - e m <tab> 
> <return>
>
> Recent messages:
> For information about GNU Emacs and the GNU system, type C-h C-a.
> Scanning for dabbrevs...100%
> dabbrev-expand: No dynamic expansion for `truncate-par' found
> Scanning for dabbrevs...100%
> dabbrev-expand: No dynamic expansion for `truncate-part' found
> Scanning for dabbrevs...100%
> dabbrev-expand: No dynamic expansion for `truncate-partial-window' found