fixed #387 - Setting viewport isn't quite synchronous

@@ -66,6 +66,7 @@ Last, all the casper test suites have been upgraded to use the new testing featu
 
 - closed [#392](https://github.com/n1k0/casperjs/issues/392) - `--direct` & `--log-level` options available for the `casperjs` executable
 - closed [#350](https://github.com/n1k0/casperjs/issues/350) - Add a Casper.waitForSelectorTextChange() method
+- fixed [#387](https://github.com/n1k0/casperjs/issues/387) - Setting viewport isn't quite synchronous
 
 2013-02-08, v1.0.2
 ------------------

@@ -1645,13 +1645,15 @@ Casper.prototype.userAgent = function userAgent(agent) {
 };
 
 /**
- * Changes the current viewport size.
+ * Changes the current viewport size. That operation is asynchronous as the page
+ * has to reflow its contents accordingly.
  *
- * @param  Number  width   The viewport width, in pixels
- * @param  Number  height  The viewport height, in pixels
+ * @param  Number    width   The viewport width, in pixels
+ * @param  Number    height  The viewport height, in pixels
+ * @param  Function  then    Next step to process (optional)
  * @return Casper
  */
-Casper.prototype.viewport = function viewport(width, height) {
+Casper.prototype.viewport = function viewport(width, height, then) {
     "use strict";
     this.checkStarted();
     if (!utils.isNumber(width) || !utils.isNumber(height) || width <= 0 || height <= 0) {
@@ -1662,7 +1664,7 @@ Casper.prototype.viewport = function viewport(width, height) {
         height: height
     };
     this.emit('viewport.changed', [width, height]);
-    return this;
+    return utils.isFunction(then) ? this.then(then) : this;
 };
 
 /**

 /*global casper*/
 /*jshint strict:false*/
+var utils = require('utils');
+
 casper.test.begin('viewport() tests', 3, function(test) {
     casper.start();
     casper.viewport(1337, 999);
@@ -11,3 +13,22 @@ casper.test.begin('viewport() tests', 3, function(test) {
         'Casper.viewport() validates viewport size data');
     test.done();
 });
+
+casper.test.begin('viewport() asynchronous tests', 2, function(test) {
+    var screenshotData;
+
+    casper.start('tests/site/index.html').viewport(800, 600, function() {
+        this.setContent(utils.format('<img src="data:image/png;base64,%s">',
+                                     this.captureBase64('png')));
+    });
+
+    casper.then(function() {
+        var imgInfo = this.getElementInfo('img');
+        test.assertEquals(imgInfo.width, 800, 'Casper.viewport() changes width asynchronously');
+        test.assertEquals(imgInfo.height, 600, 'Casper.viewport() changes height asynchronously');
+    });
+
+    casper.run(function() {
+        test.done();
+    });
+});