Add move_before() convenience method for GridFilterSet

to more easily rearrange sort order of grid filters

tailbone/grids/filters.py

@@ -770,6 +770,28 @@ class GridFilterSet(OrderedDict):
     Collection class for :class:`GridFilter` instances.
     """
 
+    def move_before(self, key, refkey):
+        """
+        Rearrange underlying key sorting, such that the given ``key`` comes
+        just *before* the given ``refkey``.
+        """
+        # first must work out the new order for all keys
+        newkeys = []
+        for k in self.keys():
+            if k == key:
+                continue
+            if k == refkey:
+                newkeys.append(key)
+                newkeys.append(refkey)
+            else:
+                newkeys.append(k)
+
+        # then effectively replace dict contents, using new order
+        items = dict(self)
+        self.clear()
+        for k in newkeys:
+            self[k] = items[k]
+
 
 class GridFiltersForm(forms.Form):
     """