=========================================================================================
- Long overdue refactor to avoid repetition during save/restore and copy.
- New interface to notify an extension when it is attached. It also enables the extension to gain
a pointer to the geometry container. This is intended to extend the functionality already existing
in Part::Geometry.
===================================================
Currently the ID is a unique number without an specific use and it is
conceived to be taken over by future RT's Sketcher PRs.
Because of this, and not to interfere with RT's implementation, it is
not stored, but will be restored if attribute available.
Unrelated:
Similarly, ExternalGeometryExtension is also there conceived for RT's
future sketcher PRs, but it is not used.
==================================================================
GeometryExtension was originally designed to be serializable (save/restore). However,
GeometryMigrationExtension and ViewProviderSketchGeometryExtension have demonstrated the
usefulness of runtime-only GeometryExtensions.
The problem with runtime-only extensions being of a serializable type (GeometryExtension before
this commit) arises when Part::Geometry is to serialize the extensions and serialise the number
of extensions the geometry has. If runtime-only GeometryExtensions do not save a tag, then the
restore mechanism will expect more extensions that are actually in the XML file.
This commit makes GeometryExtension by default not serializable and deriving directly from
Base::BaseClass. A new class GeometryPersistentExtension is created, deriving from GeometryExtension
to provide serialisation. All Extensions requiring serialization derive from GeometryPersistentExtension
and those not requiring it from GeometryExtension directly.
This commit adapts all extensions to the new situation:
Part: GeometryDefaultExtension
Part: GeometryMigrationExtension
Sketcher: ViewProvierSketchGeometryExtension
Sketcher: SketchGeometryExtension and ExternalGeometryExtension
=============================================================================
Minor refactoring to centralise string to enum conversion in a single place
============================================================
This commit extends SketchGeometryExtension to store within a Geometry if it is an internal aligment geometry
and which type.
std::move is redundant when it is used to return a local object from a function (eg return std::move(local)): indeed, returning a local object from a function implicitly moves it. Moreover using std::move this way
See https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rf-return-move-local
However, in order to avoid -Wreturn-std-move as well, a Base object is move-constructed
from Derived when required.
