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
+
+
+class PreferenceLayout(Layout):
+    """django-material Layout object for managing preferences."""
+
+    def __init__(self, form_base_class, section=None):
+        """
+        Create 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))
+        super().__init__(*rows_material)