Re: displaying missing glyphs

[Leo Butler <leo.butler@umanitoba.ca>]

<2QdxY4RzWzUUiLuE@potatochowder.com> writes:

>
> On 2021-04-12 at 12:08:08 -0500,
> Regarding "Re: displaying missing glyphs,"
> Leo Butler <leo.butler@umanitoba.ca> wrote:
>
>> Andreas Eder <a_eder_muc@web.de> writes:
>> 
>> > On Fr 09 Apr 2021 at 11:32, Leo Butler <leo.butler@umanitoba.ca> wrote:
>> >
>> >> I use `emacs -nw` inside of screen inside of uxterm. Unfortunately, many
>> >> unicode glyphs are not displayed correctly (although they are if I
>> >> attach the screen session in gnome-terminal, for example).
>> >>
>> >> In emacs/elisp, how might I override the default empty box to display
>> >> something more informative?
>> >
>> > The problem is - most likely - a font that is not unicode capable.
>> > If you set uxterm to ise the same font as gnome-terminal then it should
>> > work.
>> > The same combination (uxterm, screen and emacs) works perfectly well
>> > here.
>> 
>> Thanks for the suggestion. I have attached a marked-up screen shot of an
>> xterm (left) and gnome-terminal running `emacsclient -nw` and showing
>> the same buffer. You can see there is a noticeable clipping of some of
>> the characters in the xterm.
>> 
>> According to lsof, gnome-terminal is using
>> 
>>  /usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf
>> 
>> so the xterm has been run using
>> 
>> xterm -fa 'DejaVuSansMono' -fs 9
>> 
>> (and all font-related options are commented out in ~/.Xdefaults).
>> 
>> FWIW, this is on a debian testing system with XTERM_LOCALE=en_US.UTF-8.
>
> At startup time, both programs have to determine the size of a character
> cell.  They do so by applying some algorithm to the font(s) involved
> (the maximum width of all glyphs?  the average width of selected glyphs?
> something else?).  Evidently, xterm's algorithm doesn't account for all
> the glyphs, and ends up clipping some of them, whereas gnome-terminal
> has a different algorithm.

That seems like a reasonable answer, although, because I am ignorant of
all things font-related, I would have thought the font would have
contained this information.

>
> You clipped the xterm and gnome-terminal windows.  Are they the same
> size?

The two windows share 50% of the width of my screen. I used gimp to
select the whole screen, but I may have missed a few pixels on the
margins. Also, the WM (fluxbox) seems to create a 2-3 pixel-wide overlap
for reasons that escape me and this is consistent across applications.

>   Does the gnome-terminal contain more pixels (because it accounts
> for the wider glyphs)?

xwininfo shows the left window is 2 pixels wider than the right (800 v
798). If I give each window 799 pixels, I still see the same behaviour.

Leo