frontends (xmlui): cancelling form now trigger submit with {"cancelled": "true"} instead of being silently ignored

frontends/src/tools/xmlui.py

@@ -663,6 +663,11 @@ class XMLUIPanel(XMLUIBase):
     def onFormCancelled(self, ignore=None):
         """Called when a form is cancelled"""
         log.debug(_("Cancelling form"))
+        if self.submit_id is not None:
+            data = {C.XMLUI_DATA_CANCELLED: C.BOOL_TRUE}
+            self.submit(data)
+        else:
+            log.warning(_("The form data is not sent back, the type is not managed properly"))
         self._xmluiClose()
 
     def onSaveParams(self, ignore=None):