Add layer-swipe example

examples/layer-swipe.js

@@ -0,0 +1,47 @@
+goog.require('ol.Map');
+goog.require('ol.RendererHint');
+goog.require('ol.View2D');
+goog.require('ol.layer.Tile');
+goog.require('ol.source.BingMaps');
+goog.require('ol.source.OSM');
+
+var osm = new ol.layer.Tile({
+  source: new ol.source.OSM()
+});
+var bing = new ol.layer.Tile({
+  source: new ol.source.BingMaps({
+    key: 'Ak-dzM4wZjSqTlzveKz5u0d4IQ4bRzVI309GxmkgSVr1ewS6iPSrOvOKhA-CJlm3',
+    style: 'Aerial'
+  })
+});
+
+var map = new ol.Map({
+  layers: [osm, bing],
+  renderer: ol.RendererHint.CANVAS,
+  target: 'map',
+  view: new ol.View2D({
+    center: [0, 0],
+    zoom: 2
+  })
+});
+
+var swipe = document.getElementById('swipe');
+
+bing.on('precompose', function(event) {
+  var ctx = event.getContext();
+  var width = ctx.canvas.width * (swipe.value / 100);
+
+  ctx.save();
+  ctx.beginPath();
+  ctx.rect(width, 0, ctx.canvas.width - width, ctx.canvas.height);
+  ctx.clip();
+});
+
+bing.on('postcompose', function(event) {
+  var ctx = event.getContext();
+  ctx.restore();
+});
+
+swipe.addEventListener('change', function() {
+  map.requestRenderFrame();
+}, false);