I second @wonder-sk, no need to introduce Qgis::SCALE_PRECISION, it's only used in one place and doesn't clarify the code.

addZvalue() should be sufficient.

I don't see why, while specifying that this is a PointZ, we still must give the default z-value. The ctor is the best place for init with defaults.

IMO the 3rd value in QgsPointV2 ctor should be Z coordinate. Or implicit conversion from {x,y,z}. That, or a QgsPointV2::createWithZ(real, real, real) static.

do we need to expose that here if it's a global setting ?

I guess that should be `double defaultZValue() const;`?

Can we change `p` to `point`? It would be nice to have a more verbose api in 3.0. Is that point changed within the method? If not, that should be `const QgsPointV2& point`

Hi, that could be rename from "Geometries with Z coordinate" to "Geometries with Z/M coordinate" since M is also saved apparently

Nicer ui would be to disable (and clear) the mGeometryWithZCheckBox checkbox if the geometry type is set to none by the user.

This won't work - geomType will never be null. It should be instead: if ( geometryType == QgsWkbTypes::NoGeometry )

QGIS convention is not to name getters with a "get" prefix. This should be: double defaultZValue() const;

"default". A description of when this is used and how it is set would also be useful.

Seems odd to me to store this value in a member variable. Why not just modify getDefaultZValue() to retrieve the settings value? This would allow the default to be changed and immediately reflected.

Can you add a description of what this constant represents to the docs