Re: displaying missing glyphs

[2QdxY4RzWzUUiLuE@potatochowder.com]

On 2021-04-12 at 13:45:20 -0500,
Regarding "Re: displaying missing glyphs,"
Leo Butler <leo.butler@umanitoba.ca> wrote:

> <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.

Okay, the windows are the same size in pixels, but look at the number of
characters on a line.  The xterm window includes more characters, which
means that the gnome-terminal window includes more pixels per character
(the gnome-terminal window cuts your command off in the middle of the
closing parenthesis of the call to format).

I don't think emacs has anything to do with it.