- * A function to be called to transform the source property of @source
- * from @source_value into the target property of @target
- * using @target_value.
+ * A function to be called to transform @from_value to @to_value. If
+ * this is the @transform_to function of a binding, then @from_value
+ * is the @source_property on the @source object, and @to_value is the
+ * @target_property on the @target object. If this is the
+ * @transform_from function of a %G_BINDING_BIDIRECTIONAL binding,
+ * then those roles are reversed.