Hi Marius, Thank you for creating the API! I am still trying to figure out how to display the gwt tree edit panel in the WYSIWYG editing mode. Is it correct that I use the new api like last time you told me? Please see the code below: native void setBackgroudColor(String color) /*-{ editorJSReference.execute('backcolor', color); }-*/; and if (((TreeItem)event.getSelectedItem()).getText().equals("Alternative")) { setBackgroudColor("yellow"); } What do you think? Do you think that will work? Thank you! Hope I could get it done before meeting in the coming week. Otherwise, my advisors will give me unhappy look again =_= If there are anything I could help free feel to let me know, like documenting how to use your new background API. Remember you have to create the page for me first. Leon