Add getStylePreview

src/style_manager/model/PropertyStack.js

@@ -213,6 +213,17 @@ export default class PropertyStack extends PropertyComposite {
       : style;
   }
 
+  getStylePreview(layer, opts = {}) {
+    let result = {};
+    const preview = this.get('preview');
+
+    if (preview) {
+      result = this.getStyleFromLayer(layer, opts);
+    }
+
+    return result;
+  }
+
   /**
    * Get layer separator.
    * @return {RegExp}

src/style_manager/view/LayerView.js

@@ -112,7 +112,7 @@ export default View.extend({
 
     if (pModel.get('preview')) {
       const prvEl = this.getPreviewEl();
-      const style = pModel.getStyleFromLayer(model, { number: { min: -3, max: 3 } });
+      const style = pModel.getStylePreview(model, { number: { min: -3, max: 3 } });
       const styleStr = keys(style)
         .map(k => `${k}:${style[k]}`)
         .join(';');