SimpleGesture is a Vaadin (and plain GWT) component for mouse gesture recognition. It uses a simple, but accurate, algorithm for gesture recognition, which represents the gesture as a human (well, programmer) readable string. The gesture is encoded with numbers representing directions (left-right would be "40", see screenshot), and matching is done using the Levenshtein distance algorithm, which also tells you how closely the gesture was matched. SimpleGesture also supports recording and detection of similar gestures. See links for more details, and a demo.