Add splitValues helper function to style Property

src/style_manager/model/Property.js

@@ -135,6 +135,20 @@ const Property = Backbone.Model.extend(
       return result;
     },
 
+    /**
+     * Helper function to safely split a string of values.
+     * Useful when style values are inside functions
+     * eg:
+     * -> input: 'value(1,2,4), 123, value(4,5)' -- default separator: ','
+     * -> output: ['value(1,2,4)', '123', 'value(4,5)']
+     * @param {String} values Values to split
+     * @param {String} [separator] Separator
+     */
+    splitValues(values, separator = ',') {
+      const sep = new RegExp(`${separator}(?![^\\(]*\\))`);
+      return (values || '').split(sep).map(i => i.trim());
+    },
+
     /**
      * Get the default value
      * @return {string}

src/style_manager/view/PropertyStackView.js

@@ -241,7 +241,8 @@ export default PropertyCompositeView.extend({
     }
 
     const toAdd =
-      model.getLayersFromTarget(target, { resultValue }) || layersObj;
+      model.getLayersFromTarget(target, { resultValue, layersObj }) ||
+      layersObj;
     layers.reset();
     layers.add(toAdd);
     model.set({ stackIndex: null }, { silent: true });