The behavior of the Draft_SelectGroup command was a bit cryptic. Layers were also regarded as groups. And the selection result was not the same if a nested object, instead of the group that object was in, was selected. The new version selects all objects in the `Group` property of the selected groups (or group-like objects). Nested groups are selected, but their contents is not.
Fix 3 issues with the Draft Tray layer list:
The layer list should display even if there are no layers so that the "Add new Layer" option can be selected.
"Project" and "BuildingPart" objects should be added to the list (depending on "AutogroupAddGroups" of course).
The "LayerContainer" object should not be added to the list. Although it is in fact a group, it is just too confusing.
The code that was intended to handle this preference looked inside
Mod/BIM instad of Mod/Draft for the preference. This seems to have been
broken since the preference was first introduced in commit 507c40669d
(Draft: Turned autogroup button into layers selector (added pref option
to restore old groups-based system)).
This also removes a stray "-" that was probably a leftover from a merge
conflict, introduced in commit 68119de02f (Draft: move Draft_AutoGroup to
gui_groups module). Since -True is still true and -False is still false,
this did not actually break the code, though.
See https://forum.freecadweb.org/viewtopic.php?t=42018 for related
discussion.
These functions were previously in `draftutils.utils`,
and are related to grouping objects and finding objects
inside groups. These include `get_group_names`, `ungroup`,
`get_windows`, `get_group_contents`, `get_movable_children`.
These are imported in the main `Draft.py` module, so compatibility
is retained.
Modules which use these functions are updated; these include
Gui Commands like `Move`, `Rotate`, `Scale`, `AddToGroup`,
as well as objects like `DrawingView` and `Shape2DView`,
and `ViewProviderClone`.
The code inside the `importDXF` module is also updated.
The Arch Workbench uses many of these functions
but it does so from the `Draft` namespace, so these edits
don't change the situation for these commands.
In Python 3 `super()` can be used without an argument
in order to get the parent class, `super()`.
In Python 2 the present class must be used as an argument,
`super(ThisClass, self)`.
This commit is done to support Python 2,
as without it all Gui Command tools will be broken
and will fail to launch, even if the unit tests pass.
Also, set the `__metaclass__` variable to `type`.
This is done to turn all classes into "new style" classes
in Python 2. This is required so `super()` works correctly
in this version of Pyton.
This commit can be reverted once Python 2 support
is completely dropped, and only Python 3 compatible code
is used.
