min-width display property, but with padding at the start

min-width display property, but with padding at the start

[Spencer Baugh]

I'm writing a mode which adds an entry to the mode-line containing a
number.  This number can rapidly grow or shrink (it's a number of build
targets left to build, for a build system like Bazel) so I would like to
pad it to a specified width, to avoid the mode-line jittering around as
the number changes.

Adding a `display' property with the value '(min-width (5.0)) works
fine.

However, min-width pads by adding padding at the end.  I'd like to add
padding at the start instead.

Is there a way to achieve this with display properties?

Re: min-width display property, but with padding at the start

[Eli Zaretskii]

> From: Spencer Baugh <sbaugh@janestreet.com>
> Date: Mon, 19 Aug 2024 16:53:58 -0400
> 
> 
> I'm writing a mode which adds an entry to the mode-line containing a
> number.  This number can rapidly grow or shrink (it's a number of build
> targets left to build, for a build system like Bazel) so I would like to
> pad it to a specified width, to avoid the mode-line jittering around as
> the number changes.
> 
> Adding a `display' property with the value '(min-width (5.0)) works
> fine.
> 
> However, min-width pads by adding padding at the end.  I'd like to add
> padding at the start instead.
> 
> Is there a way to achieve this with display properties?

Why do you need display properties?  What's wrong with

  (format "%5s" THE-STRING)

?

Re: min-width display property, but with padding at the start

[Spencer Baugh]

Eli Zaretskii <eliz@gnu.org> writes:
>> From: Spencer Baugh <sbaugh@janestreet.com>
>> Date: Mon, 19 Aug 2024 16:53:58 -0400
>> 
>> 
>> I'm writing a mode which adds an entry to the mode-line containing a
>> number.  This number can rapidly grow or shrink (it's a number of build
>> targets left to build, for a build system like Bazel) so I would like to
>> pad it to a specified width, to avoid the mode-line jittering around as
>> the number changes.
>> 
>> Adding a `display' property with the value '(min-width (5.0)) works
>> fine.
>> 
>> However, min-width pads by adding padding at the end.  I'd like to add
>> padding at the start instead.
>> 
>> Is there a way to achieve this with display properties?
>
> Why do you need display properties?  What's wrong with
>
>   (format "%5s" THE-STRING)
>
> ?

That is probably what I'll do if I can't find another solution, but
doing it with display properties works with non-fixed-width characters
and faces, which a user might have configured.

If simply padding with spaces sufficed, the display properties in
(info "(elisp) Specified Space") would have little reason to exist.

Re: min-width display property, but with padding at the start

[tomas]

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On Tue, Aug 20, 2024 at 02:59:51PM +0300, Eli Zaretskii wrote:
> > From: Spencer Baugh <sbaugh@janestreet.com>

[...]

> > Is there a way to achieve this with display properties?
> 
> Why do you need display properties?  What's wrong with
> 
>   (format "%5s" THE-STRING)

This was my "inner question", too. Then I thought that some folks might
like to use proportional fonts (yeah, Computer Modern has explicit fixed
width for numerals, but not everyone's as wise as DEK ;-)

Not that I would allow a proportional font near my Emacs, ever...

Cheers
-- 
t

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Re: min-width display property, but with padding at the start

[Eli Zaretskii]

> From: Spencer Baugh <sbaugh@janestreet.com>
> Date: Tue, 20 Aug 2024 08:09:51 -0400
> 
> >> Is there a way to achieve this with display properties?
> >
> > Why do you need display properties?  What's wrong with
> >
> >   (format "%5s" THE-STRING)
> >
> > ?
> 
> That is probably what I'll do if I can't find another solution, but
> doing it with display properties works with non-fixed-width characters
> and faces, which a user might have configured.

Using variable-pitch fonts on the mode line is not recommended, as the
results could be problematic around fields that change dynamically.
The min-width property was introduced to make that easier during the
short period when we considered switching to variable-pitch font by
default, but we later decided not to do that for several reasons.

Are there many people who use variable-pitch fonts on the mode line?

> If simply padding with spaces sufficed, the display properties in
> (info "(elisp) Specified Space") would have little reason to exist.

As an alternative to min-width, you could use a :space display spec
whose width you calculate in Lisp, given string-width of the string
you want to pad.  I think this should work.

Re: min-width display property, but with padding at the start

[Spencer Baugh]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Spencer Baugh <sbaugh@janestreet.com>
>> Date: Tue, 20 Aug 2024 08:09:51 -0400
>> 
>> >> Is there a way to achieve this with display properties?
>> >
>> > Why do you need display properties?  What's wrong with
>> >
>> >   (format "%5s" THE-STRING)
>> >
>> > ?
>> 
>> That is probably what I'll do if I can't find another solution, but
>> doing it with display properties works with non-fixed-width characters
>> and faces, which a user might have configured.
>
> Using variable-pitch fonts on the mode line is not recommended, as the
> results could be problematic around fields that change dynamically.
> The min-width property was introduced to make that easier during the
> short period when we considered switching to variable-pitch font by
> default, but we later decided not to do that for several reasons.

Ah, okay, that makes sense.  I'll just use a format invocation as you
described, then.

> Are there many people who use variable-pitch fonts on the mode line?
>
>> If simply padding with spaces sufficed, the display properties in
>> (info "(elisp) Specified Space") would have little reason to exist.
>
> As an alternative to min-width, you could use a :space display spec
> whose width you calculate in Lisp, given string-width of the string
> you want to pad.  I think this should work.

Yes, that makes sense as a way to support variable-pitch fonts (although
probably a little less reliable than something supported directly by the
display engine)

Re: min-width display property, but with padding at the start

[Ihor Radchenko]

Eli Zaretskii <eliz@gnu.org> writes:

> Are there many people who use variable-pitch fonts on the mode line?

I think that it is fairly common to use various Unicode symbols or
emojis that may come from different fonts that may or may not have the
same symbol width (even if each single font is monospaced).

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>

Re: min-width display property, but with padding at the start

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: Spencer Baugh <sbaugh@janestreet.com>, emacs-devel@gnu.org
> Date: Tue, 20 Aug 2024 14:03:53 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Are there many people who use variable-pitch fonts on the mode line?
> 
> I think that it is fairly common to use various Unicode symbols or
> emojis that may come from different fonts that may or may not have the
> same symbol width (even if each single font is monospaced).

Spencer's problem was not with such symbols.

Re: min-width display property, but with padding at the start

[Ihor Radchenko]

Eli Zaretskii <eliz@gnu.org> writes:

>> > Are there many people who use variable-pitch fonts on the mode line?
>> 
>> I think that it is fairly common to use various Unicode symbols or
>> emojis that may come from different fonts that may or may not have the
>> same symbol width (even if each single font is monospaced).
>
> Spencer's problem was not with such symbols.

Yes, of course. But the topic is more broad.
I do not think that the proposed min-width property is something that is
inherently limited to using on numbers.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>

Re: min-width display property, but with padding at the start

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: sbaugh@janestreet.com, emacs-devel@gnu.org
> Date: Tue, 20 Aug 2024 14:34:27 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> > Are there many people who use variable-pitch fonts on the mode line?
> >> 
> >> I think that it is fairly common to use various Unicode symbols or
> >> emojis that may come from different fonts that may or may not have the
> >> same symbol width (even if each single font is monospaced).
> >
> > Spencer's problem was not with such symbols.
> 
> Yes, of course. But the topic is more broad.

No, it isn't, not AFAIU.  Spencer wanted to pad dynamically-generated
strings, so fixed symbols are not very relevant.

> I do not think that the proposed min-width property is something that is
> inherently limited to using on numbers.

Numbers are usually padded on the left, unlike strings.

Re: min-width display property, but with padding at the start

[Ihor Radchenko]

Eli Zaretskii <eliz@gnu.org> writes:

>> >> > Are there many people who use variable-pitch fonts on the mode line?
>> >> 
>> >> I think that it is fairly common to use various Unicode symbols or
>> >> emojis that may come from different fonts that may or may not have the
>> >> same symbol width (even if each single font is monospaced).
>> >
>> > Spencer's problem was not with such symbols.
>> 
>> Yes, of course. But the topic is more broad.
>
> No, it isn't, not AFAIU.  Spencer wanted to pad dynamically-generated
> strings, so fixed symbols are not very relevant.

Unicode symbols can also be dynamically generated.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>

Re: min-width display property, but with padding at the start

[Petteri Hintsanen]

Eli Zaretskii <eliz@gnu.org> writes:

> Are there many people who use variable-pitch fonts on the mode line?

I do.  Haven't spotted any problems, although I haven't looked too
closely either.

FWIW, Emacs tsdh-dark theme uses also variable pitch font on the mode
line.

Thanks,
Petteri

Re: min-width display property, but with padding at the start

[Jim Porter]

On 8/20/2024 6:28 AM, Eli Zaretskii wrote:
>> That is probably what I'll do if I can't find another solution, but
>> doing it with display properties works with non-fixed-width characters
>> and faces, which a user might have configured.
[snip]
> Are there many people who use variable-pitch fonts on the mode line?

For what it's worth, I could see 'visual-wrap-line-mode' + SHR/EWW using 
this. If I make an ordered list like so,

   1. Here is
      some text
   2. Here is
      some more
   ...
   10. Here is
       even more

the two-digit items won't line up. It's not hard to compute the max 
number of characters for the numbers, but then you'd end up with:

   1.  Here is
       some text
   ...
   10. Here is
       even more

It'd be nice to right-align the numbers. As you mention up-thread, we 
could do this today via 'format', but that only works because SHR 
currently uses a fixed-pitch font for item numbers no matter what. (I'd 
like to change that so the fonts in EWW are consistent.)

That's not to say we need to add this feature; but if it existed 
already, I'd probably be tinkering with it right now. :)