> > > > > I've recently started using urxvt instead of xterm everywhere,
> > > > > in major part because xterm was losing glyphs, and after a few months
> > > > > of not figuring out why (and asking the guys in charge of X11 and drm
> > > > > I didn't get any useful answer for my setup) I decided to switch.
> > > > >
> > > > 
> > > > I not completley understand what do you mean as "losing glyphs" but if you
> > > > mean text on resize of screen...
> > > 
> > > No, it's just some glyphs on my xterm that would randomly not show. With
> > > absolutely zero error messages and randomness. And it would happen after
> > > a while, that could be some random e that would not show. Quite infuriating.
> > I also don't understand the problem you explain.  Some questions:
> > 
> >   - Does it happen with unicode only or also with ascii?
> 
> Basic ascii letters.

As in, the xterm window would display something like "l tt r"?
Can you please a xwd(1) of the xterm window?

> The symptom is that after a while of gfx use (lots of mpv running here),
> some terminals would randomly lose letters...

Will it lose all instances of the given letter in the given xterm window?
Or just some of them? Or in all the xterm windows all instances of "letter"
would suddenly become "l tt er"?

> Some ascii glyphs would stop rendering,

Meaning no new instances will have the glyph,
or will it also disappear from the previous instances already displayed?

> Opening another xterm would restore normalcy for a bit of time.

Meaning, the new xterm will behave correctly, or will also
the already running xterms start behaving correctly?
Will the missing glyphs re-appear in the blank spaces?

> Never got any idea how to debug it... perfectly silent error, no message
> in any log, and couldn't figure out what to set to make it emit actual
> errors.

Have you tried setting fontWarnings or forceBoxChars?

  When “false”, xterm also shows a blank where otherwise
  printable glyphs are missing from the current font.

  When “true”, xterm also shows a dashed box outline where
  otherwise printable glyphs are missing from the current font.

(Not that I think your font fails to load
or some glyphs suddenly become missing.)

Anyway, I have never seen such behaviour.

Jan