bug#52324: 29.0.50; "Padded" mode line lacks uniform border

[Protesilaos Stavrou]

On 2021-12-06, 16:47 +0200, Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Protesilaos Stavrou <info@protesilaos.com>
>> Date: Mon, 06 Dec 2021 10:58:02 +0200
>> 
>> In an emacs -Q session with version 27 we could evaluate the following
>> to make the mode line look more spacious ("padded", so to speak):
>> 
>>     (setq x-underline-at-descent-line t)
>> 
>>     (set-face-attribute 'mode-line nil
>>                         :foreground "black"
>>                         :background "gray80"
>>                         :box '(:line-width 6 :color "gray80")
>>                         :overline "gray30"
>>                         :underline "gray30"
>>                         :distant-foreground 'unspecified)
>> 
>> Whereas with master, the same results in a box with interrupted lines.
>
> This seems to be a general bug regarding display of stretches of
> whitespace with overline and underline.  In Emacs 27, after evaluating
> the above settings, try this:
>
>    M-: (setq mode-line-format "%b             %p HELLO") RET
>
> where the whitespace between %b and %p is 2 TAB characters.  you will
> see that the stretch glyph produced for the TABs lacks the overline
> and underline in Emacs 27 as well.
>
> So this is not a bug introduced by the recent changes in the mode
> line, it is a bug that was always in Emacs, and those recent changes
> just exposed it.
>
> I'll try to dig into this when I have time.

I see.  Thanks!

>> Furthermore, there exists an invisible button (?) to the left of the
>> "All" text.  The emacs-29-mode-line-padded-mouse-pointer-button.png
>> shows it and also captures the tooltip.  (Maybe these are related to the
>> same underlying change on how the mode line is produced, otherwise I can
>> file a separate bug report).
>
> I think that's a separate bug, so please file a separate report for
> it.

Did that in bug#52332.

-- 
Protesilaos Stavrou
https://protesilaos.com