restrict point movement
restrict the area the point can be dragged on
HTML
<script src="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraphcore.js"></script>
<link rel="stylesheet" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css">
<div id="jxgbox" style="width: 500px; height: 500px;"></div>
JavaScript
var board = JXG.JSXGraph.initBoard('jxgbox', {boundingbox: [-10, 10, 10, -10], axis: true,showNavigation:true});
var l = board.create('line', [[0, 0], [1, 0]], {straightFirst: false, visible: false});
var g = board.create('glider', [l]);