Resolve "Add option to define rows for preferences forms"

Closes #337 (closed)

aleksis/core/util/forms.py

+from collections import OrderedDict
+
+from material import Layout, Row
+
+
+def preference_layout_builder(form_base_class, section=None):
+    """
+    Return a django-material Layout object for the given form_base_class.
+
+    :param form_base_class: A Form class used as the base. Must have a ``registry` attribute
+    :param section: A section where the layout builder will load preferences
+    """
+    registry = form_base_class.registry
+    if section:
+        # Try to use section param
+        preferences_obj = registry.preferences(section=section)
+
+    else:
+        # display all preferences in the form
+        preferences_obj = registry.preferences()
+
+    rows = OrderedDict()
+
+    for preference in preferences_obj:
+        row_name = preference.get("row", preference.identifier())
+        rows.setdefault(row_name, [])
+        rows[row_name].append(preference.identifier())
+
+    rows_material = []
+    for fields in rows.values():
+        rows_material.append(Row(*fields))
+    return Layout(*rows_material)