--- a/svghmi/widgets_common.ysl2	Wed May 13 14:48:52 2020 +0200
+++ b/svghmi/widgets_common.ysl2	Thu May 14 09:24:09 2020 +0200
@@ -65,13 +65,16 @@
 emit "preamble:widget-base-class" {
     ||    
     class Widget {
+        offset = 0;
+        frequency = 10; /* FIXME arbitrary default max freq. Obtain from config ? */
         constructor(elt_id,args,indexes,members){
+            this.element_id = elt_id;
             this.element = id(elt_id);
             this.args = args;
             this.indexes = indexes;
-            this.offset = 0;
             Object.keys(members).forEach(prop => this[prop]=members[prop]);
         }
+
         unsub(){
             /* remove subsribers */
             for(let index of this.indexes){