bug#19395: 25.0.50; Setting left fringe to 0 messes up window-width

[Titus von der Malsburg <malsburg@posteo.de>]

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On 2014-12-16 Tue 12:09, Eli Zaretskii wrote:
>> From: Titus von der Malsburg <malsburg@posteo.de>
>> Date: Tue, 16 Dec 2014 12:01:45 -0800
>> 
>> 
>> - emacs -Q
>> - (set-fringe-mode '(0 . 2))
>>   The left fringe has to be zero, the right fringe doesn't seem to matter.
>> - Fill a line completely with n characters such that it doesn't break.
>> - (window-width) reports n+1 characters instead of n.
>
> The n+1st character is usurped for the continuation glyph.  This is
> not a bug.

Sorry, but I don't understand that.  If (window-width) says there is
space for 50 characters and I put 50 characters on a line, there
shouldn't be a continuation character in the first place.  Also, I don't
see why I should get different behaviour for different values of
left-fringe.  When left-fringe is > 0, I get as many characters on a
line as (window-width) reports.  But if left-fringe is 0, I get one
character less on the line.  This behaviour doesn't seem to be
consistent with the documentation of window-width.  Quote:

  The return value does not include any vertical dividers, fringes or
  marginal areas, or scroll bars.

My understanding of this is that the fringes should not matter at
all.  If window-with reports n, I should be able to fit n characters on
a line irrespective of what the fringes are.  Moreover, why is this
specific to the left-fringe?  The value of right-fringe does not affect
influence whether I can get (window-width) or (window-width) -1
characters on a line.

  Titus

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