libksane seems to break QProcess::start calls

[Tobias Leupold]

> It shouldn't have any side-effects. In fact, the code exists to *avoid*
> side-effects in the first place.
>
> Of course, it assumes that there isn't buggy code elsewhere. If there is,
> then all bets are lost. I'm not going to document how to bugfix other code,
> especially complex code like this. And we've already established that the
> SANE backend is buggy.

Sorry, I got that wrong. I thought that always if one subclasses a QProcess, 
one would have to care about implementing some virtual functions to get it 
working correctly.

If it's only the SANE backend that breaks this, you're of course right.

> > If you're really bored some time, maybe you want to file an issue for the
> > SANE Pixma backend and tell the devs what exactly is wrong there and/or
> > how to fix this?
> 
> I'm not. I'll explain if you file or if you want to actually fix, but I
> don't have that much free time available.

Within what I could grasp, I filed an issue:
https://gitlab.com/sane-project/backends/-/issues/582

I fear fixing this is far beyond my programming skills. I hardly understand 
what's going on here at all ...

> Well, if you use QProcess to call the full SANE backend, that will also
> avoid the problem.

Yeah, maybe if I would acquire the images not by using libksane, but by 
calling scanimage via QProcess, I would not have any problem. But apart from 
losing the functionality I wanted to implement (setting the scanner options in 
a nice GUI way) that would only work around the real problem, which is a buggy 
implementation of the plustek backend, wouldn't it?

> "If you write buggy code, the application may misbehave" is not
> documentation.

Let's hope the SANE devs fix it ;-)