Re: [PATCH 1/5] python/utils: add add_visual_margin() text decoration utility

[John Snow <jsnow@redhat.com>]

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On Thu, Mar 3, 2022, 5:43 PM Eric Blake <eblake@redhat.com> wrote:

> On Thu, Mar 03, 2022 at 03:58:58PM -0500, John Snow wrote:
> > >>> print(add_visual_margin(msg, width=72, name="Commit Message"))
> > ┏━ Commit Message ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> > ┃ add_visual_margin() takes a chunk of text and wraps it in a visual
> > ┃ container that force-wraps to a specified width. An optional title
> > ┃ label may be given, and any of the individual glyphs used to draw the
> > ┃ box may be replaced or specified as well.
> > ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
>
> I see you dropped the right margin compared to earlier versions, but
> agree that this is still a nice visual indicator, and probably easier
> to maintain in this form.  And it got rid of the weird spacing on the
> left when the wrap point hit at the wrong time.
>
> > +    Decorate and wrap some text with a visual decoration around it.
> > +
> > +    This function assumes that the text decoration characters are single
> > +    characters that display using a single monospace column.
> > +
> > +    ┏━ Example
> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> > +    ┃ This is what this function looks like with text content that's
> > +    ┃ wrapped to 72 characters. The right-hand margin is left open to
> > +    ┃ acommodate the occasional unicode character that might make
> > +    ┃ predicting the total "visual" width of a line difficult. This
> > +    ┃ provides a visual distinction that's good-enough, though.
> > +
> ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
>
> Yep - hand-waving away Unicode messiness is certainly easiest ;)
>

I started reading the unicode specification for determining the number of
"visual grapheme clusters" in a string, got a headache, and gave up.

(See also the PyPI package "grapheme", which was last updated for unicode
13.0 and appears unmaintained. It's no small amount of code!)

I could write a function that gives a *pretty good estimate*, but I don't
want to maintain something like that.

Urwid has functions that give *great* estimates, but I'd like to avoid
dependencies.

Leaving the right margin open was the quickest, cleanest hack :) I'm amazed
at how hard this is to accomplish.

(See https://hsivonen.fi/string-length/ which ought to be required reading
in all CS classes from now on.)

Ultimately I took both this decoration and the exception code into utils as
an admission of guilt and a pledge to maintain what I did write ;)


> Reviewed-by: Eric Blake <eblake@redhat.com>
>
> [take with a grain of salt - my python is weak. But as you said in the
> cover letter, it's fairly straightforward to reproduce an environment
> where you can see it in action for hands-on testing]
>

I've long since given up on anyone understanding the Python I write.
Eduardo did, so he quit. 😅

Thanks for the reviews.


>
> --
> Eric Blake, Principal Software Engineer
> Red Hat, Inc.           +1-919-301-3266
> Virtualization:  qemu.org | libvirt.org
>
>

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