Allow toggling voice navigation while navigation is active

[otsaloma]

i.e. get rid of the enabled below.

whogo-maps/qml/NavigationPage.qml

Lines 203 to 209 in 884ed83

	TextSwitch {
	id: voiceNavigationSwitch
	checked: app.conf.get("voice_navigation")
	enabled: !app.navigationActive
	text: app.tr("Voice navigation instructions")
	onCheckedChanged: enabled && app.conf.set("voice_navigation", voiceNavigationSwitch.checked);
	}

I just don't quite remember why this needed to locked – @rinigus: your code, do you remember? Given the pregeneration, turning it on might have a slight delay, but that should be no big deal, and turning it off would still serve previously generated audio, but we can add a simple check on the QML side to ignore those. Anything else?

[rinigus]

@otsaloma - not from the top of my head. I will look tonight and see why was it. I can only speculate that its due to the lag in generation of sound files, but I'll have to check the details. Let me come back to you with it.

[rinigus]

Looked into the code a bit. If we want to do it on-fly, we'll have to call map.initVoiceNavigation . Other than that, I don't see why it shouldn't work. As you pointed out, we have verbal instructions anyway and user should expect some small delay...

While reading through the source, I could see that rerouting messages are created at each call of _get_voice_uri. In reality, its cached and not regenerated, but we could still move them maybe into set_voice

[otsaloma]

OK, I'll do this via a PR and ping you when done so you can look it over too.

[rinigus]

Will be happy to.

[otsaloma]

This looked straight-forward, so I skipped the PR. Anyway, you can look over those two commits. As far as I can tell there's just three things needed:

1. Don't play sound if voice navigation off (added, first commit)

2. Don't generate new WAVs if voice navigation off (already existed)

3. Reinitialize the voice generator if toggled on while navigation is active (added, second commit)