OSNews

Apple Dashboard widget support is being worked on by Aaron and Zack, literally as we speak. Well, maybe not literally - but when they wake up, in a few hours time So it shouldn't be long now, especially now that one of the dependencies (Qt 4.4, with integrated Webkit) is now in KDE SVN trunk.

Widget Plug-Ins

If you need to dig deeper into the system, or if you need to tap into your own application to create a Widget that closely interacts with it, you can create your own Cocoa-based plug-in. These plug-ins work by providing a JavaScript object that's made available to the Widget.

Widget plug-ins are created in Xcode using the "Cocoa Bundle" template. Once the project has been set up, the main class of the plug-in must implement the following methods:

- (id) initWithWebView:(WebView *) webView;
- (void) windowScriptObjectAvailable:(WebScriptObject *) windowScriptObject;

The first method is called when your Widget first loads the plug-in. The second method is then called and allows you to provide a JavaScript object that your Widget can use. This bridges the gap between JavaScript and Objective-C. For example, the following implementation creates a JavaScript object with the name MyScriptObject and allows methods on that object to be called from JavaScript:

- (void) windowScriptObjectAvailable:(WebScriptObject *) windowScriptObject
{
MyScriptObject *myObj = [[MyScriptObject alloc] init];
[windowScriptObject setValue:myObj forKey:@"MyScriptObject"];
}

The object can be accessed from JavaScript as follows:

<script>
if (window.MyScriptObject) {
MyScriptObject.someMethod(someArg);
}
</script>

Using this plug-in model, you can expose most any kind functionality from the system or from your application to a Widget.
Deploying a Widget

Once you have created a Widget, the next step is to get it into the hands of your users. For a Widget to be found by the Dashboard, it needs to be located in one of the following locations:

* /Library/Widgets
* ~/Library/Widgets

Conclusion

As you can see, Dashboard provides a great new development environment. Widgets are easy and fast to create, and yet very powerful. They have full access to the Internet, can use the advanced drawing capabilities of Quartz, and the rest of the functionality available in Mac OS X. The opportunities to be creative are enormous.

WebKit for Cocoa/OS X is much broader than WebKit for Qt and to think otherwise shows you aren't looking at the same WebKit source trunk from Apple as I am.