Fixes: #16201
Changing the Group property type of layers to `App::PropertyLinkListHidden` also means that they longer occur in the InList of nested objects. This side-effect was missed in #14506.
Discussion: #13657.
This PR adds the ShapeAppearance view property to Draft Layers.
The DefaultShapeColor is used for the DiffuseColor of the ShapeAppearance material. Other material properties are not based on the preferences when a layer is created.
The old ShapeColor and Transparency properties remain (ShapeColor as a hidden property) and are kept in synch with the ShapeAppearance. This is consistent with how ShapeAppearance is implemented in Core.
The gui_layers.py and make_layer.py files do not have to be changed. They manipulate the vobj via the mentioned old properties.
Uses new material system for appearance
Each feature object now has a property called ShapeMaterial that
describes its physical properties. If it has a shape, it has a
material.
The ShapeColor attribute is replaced by a ShapeAppearance attribute.
This is a material list that describes all appearance properties, not
just diffuse color. As a list in can be used for all elements of a
shape, such as edges and faces.
A new widget is provided to allow the user to select materials in a
consistent fashion. It can also launch the material editor with its
more advanced capabilities.
These messages were perhaps originally intended as a debuggin aid but now add clutter to the output panes. Remaining messges are mostly the result of methods to display attributes of an object (which one could call from the Python console) or actually provide some information which would not be obvious from the circumstances
The current make_layer function has a `None` default for the shape color and the line color. With that value the current preference is used. This, and how the function is called, results in some confusing behaviors:
* Newly created layers will only use 2 values from the preferences when they might use 5. The latter makes more sense for the end-user IMO.
* Layers created during DXF import (for example) will have a different shape color depending on the current preferences.
* The make_layer function may reapply colors that have already been set by the view provider.
To solve this all view property related function parameter have been changed to a not None value. If a None value is supplied the view property as set by the view provider is not changed. The Layer Manager has been updated accordingly.
I realize that calling a function with 6 None values is not very convenient, but think it is the solution that is least likely to break other exiting code.
Additionally:
* Removed the makeLayer function. Layers were introduced in V0.19 when the naming scheme was changed to "make_*". Maybe it was created by mistake, or before the actual renaming operation started, but it is safe to remove it now.
* Removed overly verbose messages.
* gui_layers.py had a missing import (result of a previous V0.22 PR): `from draftutils import utils`.
Since Py3.11 the methods names __setstate__ and __getstate__ conflict with the method names added to the object class.
Thus rename them to 'loads' and 'dumps'
The "Merge layer duplicates" Tree view context menu option for LayerContainers did not work.
Additionally:
- Using `openTransaction` and `commitTransaction` is required for the `merge_by_name` function but also for the `add_layer` function. Otherwise undo-redo does not work properly.
- Have replaced `translate("Draft", ...)` with `_tr(...)`.
Move `make_layer` to `draftmake`; `Layer` and `LayerContainer`
to `draftobjects`; `ViewProviderLayer` and `ViewProviderLayerContainer`
to `draftviewproviders`.
The make function and the classes are imported in `Draft.py`
to support the usage of the older `VisGroup`.
