The client-side framework is based on the Google Web Toolkit (GWT), with added features and bug fixes. Vaadin is compatible with GWT to the extent of the basic GWT feature set. Vaadin Ltd is a member of the GWT Steering Committee, working on the future direction of GWT together with Google and other supporters of GWT.
Widgets and Components
Google Web Toolkit uses the term widget for user interface components. In this book, we use the term widget to refer to client-side components, while using the term component in a general sense and also in the special sense for server-side components.
The main idea in server-side Vaadin development is to render the server-side components in the browser with the Client-Side Engine. The engine is essentially a set of widgets paired with connectors that serialize their state and events with the server-side counterpart components. The client-side engine is technically called a widget set, to describe the fact that it mostly consists of widgets and that widget sets can be combined, as described later.