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- 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.
==================================================================
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
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This is a light-weight c++ only geometry extension to enable migration of information that was stored within
the Part WB and should be migrated to another WB (for example Sketcher WB)
It is designed so that a single extension can migrate different types of data (current and future).
When new data needs to be migrated, first a new enum bit is to be added to the class enum and new data members are to
be added to store the information within GeometryMigrationExtension class.
In the Restore() function restoring the data to be migrated, a GeometryMigrationExtension extension is added to the
geometry to be migrated with the data information and the corresponding enum bit set.
In the object to receive the migration data, onDocumentRestored() it is checked whether an extension of type
GeometryMigrationExtension is present, if yes, it is checked whether a bit used for migration is set and, if yes,
the data is retrieved and the GeometryMigrationExtension extension (preferably) removed from the Geometry object.
