Bingo.

https://tomscii.sig7.se/zutty/wiki/FAQ.html

"Your graphics hardware or driver is not sufficient, you need support
for GLSL ES 3.1 or better"

Think I might just avoid zutty for the foreseeable future.

The decision to default x-terminal-emulator to a program which depends
on specific levels of graphics hardware/software seems somewhat rash,
to put it very mildly indeed. In fact, it seems positively
unbelievable.

Final workaround was to run

"update-alternatives --config x-terminal-emulator"

- and set it to /usr/bin/xfce4-terminal.wrapper

After this, setting the xfce4 default terminal application to "Debian X
Terminal Emulator" works again.

Another point: I installed zutty on the older daedalus install in the
virtualbox VM. On this, zutty throws an error: "libEGL warning: DRI2:
failed to authenticate" but starts anyway. (The font is unappealing.)

On Fri, 2025-04-18 at 17:13 +0100, Peter Duffy wrote:
> Got a bit further with this.
>
> "update-alternatives --get-selections | grep terminal"
>
> - shows that the default setting for x-terminal-emulator is
> /usr/bin/zutty - and apparently that's what's throwing the weird GLSL
> error.
>
> Only found one relevant post so far:
>
> https://wiki.webevaluation.nl/xfce-terminal
>
> (In the version of daedalus running in the virtualbox VM, installed
> about 2 months ago, the alternative setting for x-terminal emulator
> is
> /usr/bin/xfce4-terminal.wrapper. And - /usr/bin/zutty doesn't
> exist.) 
>
> I've never heard of zutty before. Apparently it's quite new. I'll try
> to find out why the version on daedalus is throwing that error.
>
> https://www.linuxlinks.com/zutty-high-end-terminal-emulator-low-end-systems/
>
> On Fri, 2025-04-18 at 15:59 +0100, Peter Duffy wrote:
> > I've just been installing daedalus on an old Dell notebook, and hit
> > a
> > strange problem. (Don't think the hardware is relevant, but I could
> > be
> > wrong.)
> >
> > I left the desktop to default to xfce4 (I always use that anyway).
> > Install completed successfully. However, when I tried to open a
> > terminal via the icon on the launchpad, I got:
> >
> > "Failed to execute default terminal emulator: input/output error"
> >
> > The command executed was "exo-open --launch TerminalEmulator"
> > (which
> > I
> > think is standard for this in xfce4)
> >
> > I checked applications -> settings -> default applications ->
> > utilities
> > -> terminal emulator: set to "Debian X Terminal Emulator".
> >
> > In /usr/share/xfce4/helpers/debian-x-terminal-emulator, X-XFCE-
> > Binaries
> > is set to "x-terminal-emulator"
> >
> > If I run /usr/bin/x-terminal-emulator, it bombs with the following:
> >
> >
> >
> > Error: Compiling fragment shader:
> >
> > 0:1(10): error: GLSL ES 3.10 is not supported. Supported versions
> > are:
> > 1.00 ES, and 3.00 ES
> >
> > terminate called after throwing an instance of 'std::system_error'
> >   what():  Resource deadlock avoided
> >
> >
> >
> > At the moment, that's as far as I've got with
> > investigation/diagnosis.
> >
> > Workaround was straightforward: just set the xfce4 terminal
> > emulator
> > to
> > "xfce4-terminal".
> >
> > Weird thing is that I installed daedalus into a virtualbox VM about
> > 2
> > months ago: the terminal icon pointed to x-terminal-emulator,  and
> > x-
> > terminal-emulator worked fine. I've just done an update/upgrade on
> > it,
> > and it still works.
> >
> > Sorry if this is a well-known problem.  If not, I'm happy to raise
> > it
> > as a bug if required.
> >
> >
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