Qt6 positioning backend broken for hybris systems

[MagneFire]

Since the Qt6 port GeoClue v0 has been removed qt/qtpositioning@3e9dc43

We should figure out a different way to get GPS working again.

AsteroidOS/meta-asteroid#246 removes the geoclue enablement.

[beroset]

There are at least a couple of ways to approach this.

1. Re-add geoclue v0

The Qt5 version used geoclue v0.12.99 which is obsolete and unmaintained, and geoclue-providers-hybris. However, as mentioned above, Qt removed support for it in 2021. The geoclue-providers-hybris supports both time and location injection (tell GNSS approximate current location, if available, to speed satellite acquisition) and A-GPS (assisted GPS uses internet, if available, to speed satellite acquisition). It's not yet clear how a QtPositioning application would access these capabilities, but they exist.

So using this option would require:

1. re-adding geoclue support (could be done as a "new" plugin for QtPositioning)

Advantages

1. known and familiar mechanism
2. no adaptations required for existing AsteroidOS software using QtPositioning

Drawbacks

1. continued dependency on geoclue v0
2. it's unknown whether a known, existing problem (GNSS does not stop, draining battery) would still be present
3. continued dependency on geoclue-providers-hybris

2. Create interface to use QtPositioning geoclue2 plugin

This was proposed in 2023 to the creators of geoclue-providers-hybris but there were two substantive objections:

1. "The problem with geoclue 2 has been that it removed the support for external location providers such as this one. In order to update to a new version we'd need again a mechanism to have location providers that don't live in main geoclue repository."
2. "In addition to the lack of support external plugin mentioned in the previous comment, geoclue 2 also seems a bit limited. It does not support for example satellite info which is supported in the old geoclue but instead seems to only handle getting location."

Using this option would require:

1. rewrite/patch of geoclue2 to include some capability from geoclue-providers-hybris

Advantages

1. no changes required to QtPositioning

Drawbacks

1. effort and mechanism of extension of geoclue2 in this way are unknown
2. both HAL and binder interfaces would need to be supported
3. lose the capability to track satellite data
4. no ability to do location injection (tell GNSS approximate current location, if available, to speed satellite acquisition)
5. no ability to use A-GPS (assisted GPS uses internet, if available, to speed satellite acquisition)

3. Create interface to use QtPositioning nmea plugin

QtPositioning already ships with an nmea plugin which handles raw NMEA sentences.

Advantages

1. no changes required to QtPositioning
2. handling and parsing of NMEA sentences, including GPS, Glonass, Beidou handed by existing Qt code
3. avoids "double conversion" to/from D-Bus

Drawbacks

1. Uncertain mechanism for controlling power on/off of underlying GNSS receiver (which uses a lot of battery energy)
2. no ability to do location injection (tell GNSS approximate current location, if available, to speed satellite acquisition)
3. no ability to use A-GPS (assisted GPS uses internet, if available, to speed satellite acquisition)

4. Create new plugin for QtPositioning

This option would create a new plugin for QtPositioning that could provide both location and satellite information.

Advantages

1. no changes required to QtPositioning
2. avoids "double conversion" to/from D-Bus

Drawbacks

1. only available to Qt applications, and not to GTK or non-Qt command line applications without adaptation
2. no ability to do location injection (tell GNSS approximate current location, if available, to speed satellite acquisition)
3. no ability to use A-GPS (assisted GPS uses internet, if available, to speed satellite acquisition)