Titled frame panel for GWT (using FIELDSET and LEGEND html tags)

Answer 1

I think you're looking for CaptionPanel:

A panel that wraps its contents in a border with a caption that appears in the upper left corner of the border. This is an implementation of the fieldset HTML element.

Answer 2

I think the problem here is that you just call DOM.appendChild - this doesn't cause the TitledPanel to adopt the Widget. The normal course of action is that you extend Composite and then call initWidget(Widget widget) - inside the hood it calls widget.setParent(this);, which in turn makes the parent adopt this widget and attach it to the browser's document. However com.google.gwt.user.client.ui.Widget.setParent(Widget) is only package-visible so you can't call it from your code (after, for example, DOM.appendChild).

I'd recommend reading Widget Best Practices / Widget Building, especially the Clean up after yourself and/or look at the source code for some GWT Widgets, to get the idea how the GWT sees custom widget creation.

And, as Robert suggested, CaptionPanel is the safer route :)