Although XWT is bundled in e4, it is in fact designed, developed and tested in classic eclipse environment. It can be used in applications on top of SWT/Jface with or without eclipse platform. So the integration with standard SWT application is really straight forward.
This paragraph explains the integration concept of XWT in an existing SWT application: how an existing classic SWT applications use XWT. XWT provides some APIs to load a UI component as children of an existing Composite via the class XWT.
The customized UI "UserControl" contains a Button with a selection event.

Now integrate the above example into a new XWT component directly. See the screenshot below.

Run the application and click the button.

