Rigify: add more utility code for the upcoming face rig.

Move widget and driver utilities from the feature set and rewrite
create_circle_widget. Also increase the line length for autopep8.

1 files changed, 37 insertions, 0 deletions

diff --git a/rigify/utils/mechanism.py b/rigify/utils/mechanism.py
index b4b2d389..413d8a00 100644
--- a/rigify/utils/mechanism.py
+++ b/rigify/utils/mechanism.py
@@ -312,6 +312,11 @@ def make_driver(owner, prop, *, index=-1, type='SUM', expression=None, variables
     return fcu
 
 
+#=============================================
+# Driver variable utilities
+#=============================================
+
+
 def driver_var_transform(target, bone=None, *, type='LOC_X', space='WORLD', rotation_mode='AUTO'):
     """
     Create a Transform Channel driver variable specification.
@@ -337,6 +342,38 @@ def driver_var_transform(target, bone=None, *, type='LOC_X', space='WORLD', rota
     return { 'type': 'TRANSFORMS', 'targets': [ target_map ] }
 
 
+def driver_var_distance(target, *, bone1=None, target2=None, bone2=None, space1='WORLD', space2='WORLD'):
+    """
+    Create a Distance driver variable specification.
+
+    Usage:
+        make_driver(..., variables=[driver_var_distance(...)])
+
+    Target bone name can be provided via a 'lazy' callable closure without arguments.
+    """
+
+    assert space1 in {'WORLD', 'TRANSFORM', 'LOCAL'}
+    assert space2 in {'WORLD', 'TRANSFORM', 'LOCAL'}
+
+    target1_map = {
+        'id': target,
+        'transform_space': space1 + '_SPACE',
+    }
+
+    if bone1 is not None:
+        target1_map['bone_target'] = bone1
+
+    target2_map = {
+        'id': target2 or target,
+        'transform_space': space2 + '_SPACE',
+    }
+
+    if bone2 is not None:
+        target2_map['bone_target'] = bone2
+
+    return {'type': 'LOC_DIFF', 'targets': [target1_map, target2_map]}
+
+
 #=============================================
 # Constraint management
 #=============================================