QtSpeech and speech-dispatcher

[Sébastien Lerique]

Hello all!

I'm trying to make speech-dispatcher available in Okular. For the
moment, Okular doesn't see speech-dispatcher installed (and working with
in the shell, e.g. `spd-say "hello"`).

The original drv build log of qtspeech mentions:

--8<---------------cut here---------------start------------->8---
Running configuration tests...
Checking for Flite... no
Checking for Speech Dispatcher... no
Done running configuration tests.

Configure summary:

Qt TextToSpeech:
  Flite .................................. no
  Flite with ALSA ........................ no
  Speech Dispatcher ...................... no
--8<---------------cut here---------------end--------------->8---

And adding "speech-dispatcher" in the inputs and/or native-inputs of
qtspeech doesn't change anything (following
<https://github.com/NixOS/nixpkgs/issues/173872>
<https://github.com/NixOS/nixpkgs/pull/173941/files>). And the
speech-dispatcher path does appear in the `environment variable PATH`,
`PKG_CONFIG_PATH`, and all the others.

Next, this comment
<https://github.com/void-linux/void-packages/issues/31608#issuecomment-867884847>
hints towards a problem with access to libraries for Qt to use the
available libraries. And indeed other qt packages have many adaptations
to reposition the qt5 libs.

Debian <https://packages.debian.org/buster/qtspeech5-speechd-plugin>,
and others (e.g.
<https://github.com/hazayan/void-packages/commit/548321cd75395953b95795cebaaff2295e117997>)
also separate out the qtspeech plugins from the non-plugins -- could
this be related to the comment
<https://github.com/void-linux/void-packages/issues/31608#issuecomment-867884847>
which may say that the multiple library files won't be produced in this
case?

It seems the problem is coming from the combination of these qt build
changes, but I can't see how it could be fixed. Anybody having some
ideas?

Best, and take care!
Sébastien

PS: this has also been explored in 2022
<https://lists.gnu.org/archive/html/guix-devel/2022-11/msg00236.html>