bug#13473: 24.3.50; Display Tables doc bug

bug#13473: 24.3.50; Display Tables doc bug

[Stephen Berman]

The (elisp) Display Tables node neglects to mention that changing the
vertical-border slot does not work on graphical terminals (compare
e.g. (set-display-table-slot standard-display-table 'vertical-border
(make-glyph-code 8214)) on graphical and non-graphics-capable displays)
(whereas it does mention this difference for the truncation and wrap
slots).


=== modified file 'doc/lispref/display.texi'
*** doc/lispref/display.texi	2013-01-05 21:18:01 +0000
--- doc/lispref/display.texi	2013-01-17 10:22:19 +0000
***************
*** 5904,5910 ****
  The glyph used to draw the border between side-by-side windows (the
  default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
  when there are no scroll bars; if scroll bars are supported and in use,
! a scroll bar separates the two windows.
  @end table
  
    For example, here is how to construct a display table that mimics
--- 5904,5912 ----
  The glyph used to draw the border between side-by-side windows (the
  default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
  when there are no scroll bars; if scroll bars are supported and in use,
! a scroll bar separates the two windows.  On graphical terminals, Emacs
! uses a thin line to indicate the border, so the display table has no
! effect.
  @end table
  
    For example, here is how to construct a display table that mimics




In GNU Emacs 24.3.50.4 (x86_64-suse-linux-gnu, GTK+ Version 3.4.4)
 of 2013-01-17 on rosalinde
Bzr revision: 111542 michael.albinus@gmx.de-20130117090647-lb9mkbk6n8q142w5
Windowing system distributor `The X.Org Foundation', version 11.0.11203000
System Description:	openSUSE 12.2 (x86_64)

bug#13473: 24.3.50; Display Tables doc bug

[Noam Postavsky]

Stephen Berman <stephen.berman@gmx.net> writes:

>   The glyph used to draw the border between side-by-side windows (the
>   default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
>   when there are no scroll bars; if scroll bars are supported and in use,
> ! a scroll bar separates the two windows.  On graphical terminals, Emacs
> ! uses a thin line to indicate the border, so the display table has no
> ! effect.
>   @end table

If it's only effective on a tty display, then is the scroll bar
reference irrelevant?  AFAIK, there are never scroll bars on a tty
display anyway.

The change which introduced the text about the scroll bars is [1:
8241495da5].  It's old, has no log message, and contains many changes,
so it's unclear why that particular text was added.

[1: 8241495da5]: 1999-09-17 06:59:04 +0000
  *** empty log message ***
  https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=8241495da57ca0efed1b2e86ff693b5614e0aebd

bug#13473: 24.3.50; Display Tables doc bug

[Stephen Berman]

On Tue, 13 Feb 2018 20:18:41 -0500 Noam Postavsky <npostavs@users.sourceforge.net> wrote:

> Stephen Berman <stephen.berman@gmx.net> writes:
>
>>   The glyph used to draw the border between side-by-side windows (the
>>   default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
>>   when there are no scroll bars; if scroll bars are supported and in use,
>> ! a scroll bar separates the two windows.  On graphical terminals, Emacs
>> ! uses a thin line to indicate the border, so the display table has no
>> ! effect.
>>   @end table
>
> If it's only effective on a tty display, then is the scroll bar
> reference irrelevant?  AFAIK, there are never scroll bars on a tty
> display anyway.

I think that's right, so the above is misleading (with or without the
change).  I guess it's sufficient just to say "On graphical terminals,
this has no effect."[1] But maybe it would be helpful to say why it has
no effect (even though you see it when you use a graphical display):

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index fbf943a08c..81084d7c06 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -6988,9 +6988,10 @@ Display Tables
 
 @item 5
 The glyph used to draw the border between side-by-side windows (the
-default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
-when there are no scroll bars; if scroll bars are supported and in use,
-a scroll bar separates the two windows.
+default is @samp{|}).  @xref{Splitting Windows}.  On graphical
+terminals, this has no effect: if scroll bars are in use, a scroll bar
+separates the two windows, and if scroll bars are not in use, the
+border is a thin unbroken line.
 @end table
 
   For example, here is how to construct a display table that mimics

Steve Berman

Footnotes:
[1]  At least not on GTK+ builds.  Someone should check other toolkits
     and non-toolkit builds (I currently can't readily do that), though
     it seems unlikely they would differ on this.

bug#13473: 24.3.50; Display Tables doc bug

[martin rudalics]

 > @@ -6988,9 +6988,10 @@ Display Tables
 >
 >   @item 5
 >   The glyph used to draw the border between side-by-side windows (the
 > -default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
 > -when there are no scroll bars; if scroll bars are supported and in use,
 > -a scroll bar separates the two windows.
 > +default is @samp{|}).  @xref{Splitting Windows}.  On graphical
 > +terminals, this has no effect: if scroll bars are in use, a scroll bar
 > +separates the two windows, and if scroll bars are not in use, the
 > +border is a thin unbroken line.
 >   @end table
 >
 >     For example, here is how to construct a display table that mimics
 >

I had prepared the below.  Maybe we could reconcile them somehow.

martin


diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 7bf03b8..f7170fe 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -4485,6 +4485,16 @@ Window Dividers
  window on a minibuffer-less frame.
  @end defun

+When dividers and vertical scroll bars are both disabled for a
+specific graphical frame, Emacs separates windows on that frame with
+the help of a one-pixel wide "vertical border", see (@pxref{Scroll
+Bars,,, emacs, The Emacs Manual}).  When dividers are disabled but
+vertical scroll bars are enabled on that frame, Emacs draws these
+borders on mode lines only since the scroll bars are already
+considered sufficent for separating the windows visually.  In either
+case, borders can be dragged with the mouse in order to resize the
+adjacent windows.
+

  @node Display Property
  @section The @code{display} Property

bug#13473: 24.3.50; Display Tables doc bug

[Eli Zaretskii]

> Date: Wed, 14 Feb 2018 17:05:29 +0100
> From: martin rudalics <rudalics@gmx.at>
> Cc: 13473@debbugs.gnu.org
> 
> I had prepared the below.  Maybe we could reconcile them somehow.

Thanks, I just added a cross-reference to that node.

bug#13473: 24.3.50; Display Tables doc bug

[Eli Zaretskii]

> From: Stephen Berman <stephen.berman@gmx.net>
> Date: Wed, 14 Feb 2018 14:33:18 +0100
> Cc: 13473@debbugs.gnu.org
> 
> On Tue, 13 Feb 2018 20:18:41 -0500 Noam Postavsky <npostavs@users.sourceforge.net> wrote:
> 
> > Stephen Berman <stephen.berman@gmx.net> writes:
> >
> >>   The glyph used to draw the border between side-by-side windows (the
> >>   default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
> >>   when there are no scroll bars; if scroll bars are supported and in use,
> >> ! a scroll bar separates the two windows.  On graphical terminals, Emacs
> >> ! uses a thin line to indicate the border, so the display table has no
> >> ! effect.
> >>   @end table
> >
> > If it's only effective on a tty display, then is the scroll bar
> > reference irrelevant?  AFAIK, there are never scroll bars on a tty
> > display anyway.
> 
> I think that's right, so the above is misleading (with or without the
> change).

Careful here: the same could be said about the truncation and
continuation glyphs (and in fact, the manual actually did say that),
but it's incorrect, because those glyphs _are_ used on GUI frames when
the user disables the fringes.

So any such "irrelevancy" must be qualified by "currently" etc.,
because no one prevents us from implementing a feature whereby they
will be used.

I will soon install the following:

  @item 5
  The glyph used to draw the border between side-by-side windows (the
  default is @samp{|}).  @xref{Splitting Windows}.  This currently has
  effect only on text terminals; on graphical terminals, if vertical
  scroll bars are supported and in use, a scroll bar separates the two
  windows, and if there are no vertical scroll bars and no dividers
  (@pxref{Windows Dividers}), Emacs uses a thin line to indicate the
  border.

bug#13473: 24.3.50; Display Tables doc bug

[Stephen Berman]

On Wed, 14 Feb 2018 20:06:01 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Date: Wed, 14 Feb 2018 14:33:18 +0100
>> Cc: 13473@debbugs.gnu.org
>> 
>> On Tue, 13 Feb 2018 20:18:41 -0500 Noam Postavsky
>> <npostavs@users.sourceforge.net> wrote:
>> 
>> > Stephen Berman <stephen.berman@gmx.net> writes:
>> >
>> >>   The glyph used to draw the border between side-by-side windows (the
>> >>   default is @samp{|}).  @xref{Splitting Windows}.  This takes effect only
>> >>   when there are no scroll bars; if scroll bars are supported and in use,
>> >> ! a scroll bar separates the two windows.  On graphical terminals, Emacs
>> >> ! uses a thin line to indicate the border, so the display table has no
>> >> ! effect.
>> >>   @end table
>> >
>> > If it's only effective on a tty display, then is the scroll bar
>> > reference irrelevant?  AFAIK, there are never scroll bars on a tty
>> > display anyway.
>> 
>> I think that's right, so the above is misleading (with or without the
>> change).
>
> Careful here: the same could be said about the truncation and
> continuation glyphs (and in fact, the manual actually did say that),
> but it's incorrect, because those glyphs _are_ used on GUI frames when
> the user disables the fringes.
>
> So any such "irrelevancy" must be qualified by "currently" etc.,
> because no one prevents us from implementing a feature whereby they
> will be used.
>
> I will soon install the following:

Thanks, this is a good fix (and also addresses Martin's concern).

Steve Berman

bug#13473: 24.3.50; Display Tables doc bug

[Stefan Kangas]

Eli Zaretskii <eliz@gnu.org> writes:

> I will soon install the following:
>
>   @item 5
>   The glyph used to draw the border between side-by-side windows (the
>   default is @samp{|}).  @xref{Splitting Windows}.  This currently has
>   effect only on text terminals; on graphical terminals, if vertical
>   scroll bars are supported and in use, a scroll bar separates the two
>   windows, and if there are no vertical scroll bars and no dividers
>   (@pxref{Windows Dividers}), Emacs uses a thin line to indicate the
>   border.

That fix was installed, and there doesn't seem to be anything else to do
here.  I'm therefore closing this bug.

Best regards,
Stefan Kangas