Rigify: add support for user-defined rig packages and related utilities.

As suggested by @icappielo, and after discussion with @meta-androcto,
I start a public request to commit third-party contributions already
accepted to https://github.com/eigen-value/rigify/tree/rigify_0.6_beta

Specifically, this includes:

* User-defined rig package (feature set) support by @pioverfour.
  This allows users to install pre-packaged rig sets via zip
  files, which become accessible together with built-in rigs,
  as discussed in T52758.

  https://github.com/eigen-value/rigify/pull/1

* Modularization of python script generation, allowing rigs to
  add their own utility functions and operators to the generated
  script. This is critical to make custom rig support really
  useful.

  https://github.com/eigen-value/rigify/pull/5

* The utils.py file is split into multiple modules with a backward
  compatibility proxy for old functions.

* Automatic verification that different rigs don't try to create
  different rig settings with the same name to alleviate increased
  risk of namespace conflicts with custom rigs.

  https://github.com/eigen-value/rigify/pull/7

* New utility class that implements bone layer selection UI.

  https://github.com/eigen-value/rigify/pull/6

* New utilities to replace copy & pasted boilerplate code for
  creating custom properties, constraints and drivers.

  https://github.com/eigen-value/rigify/pull/11

Some other random changes by MAD have likely slipped through.

These changes have already been extensively discussed and accepted
into the branch by @luciorossi, so I see no reason not to commit
them to the official repository to be tested during 2.8 beta.

Reviewers: icappiello

Differential Revision: https://developer.blender.org/D4364

1 files changed, 68 insertions, 0 deletions

diff --git a/rigify/utils/collections.py b/rigify/utils/collections.py
new file mode 100644
index 00000000..25596905
--- /dev/null
+++ b/rigify/utils/collections.py
@@ -0,0 +1,68 @@
+#====================== BEGIN GPL LICENSE BLOCK ======================
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+#======================= END GPL LICENSE BLOCK ========================
+
+# <pep8 compliant>
+
+import bpy
+import math
+
+from .errors import MetarigError
+
+
+#=============================================
+# Collection management
+#=============================================
+
+def find_layer_collection_by_collection(layer_collection, collection):
+    if collection == layer_collection.collection:
+        return layer_collection
+
+    # go recursive
+    for child in layer_collection.children:
+        layer_collection = find_layer_collection_by_collection(child, collection)
+        if layer_collection:
+            return layer_collection
+
+
+def ensure_widget_collection(context):
+    wgts_collection_name = "Widgets"
+
+    view_layer = context.view_layer
+    layer_collection = bpy.context.layer_collection
+    collection = layer_collection.collection
+
+    widget_collection = bpy.data.collections.get(wgts_collection_name)
+    if not widget_collection:
+        # ------------------------------------------
+        # Create the widget collection
+        widget_collection = bpy.data.collections.new(wgts_collection_name)
+        widget_collection.hide_viewport = True
+        widget_collection.hide_render = True
+
+        widget_layer_collection = None
+    else:
+        widget_layer_collection = find_layer_collection_by_collection(view_layer.layer_collection, widget_collection)
+
+    if not widget_layer_collection:
+        # Add the widget collection to the tree
+        collection.children.link(widget_collection)
+        widget_layer_collection = [c for c in layer_collection.children if c.collection == widget_collection][0]
+
+    # Make the widget the active collection for the upcoming added (widget) objects
+    view_layer.active_layer_collection = widget_layer_collection
+    return widget_collection