WPF Activity in Xamarin Forms

I’ve recently been working on extending an existing product written in Xamarin Forms to Windows desktop and this has meant learning a lot more about the WPF implementation. Originally Xamarin Forms was created for mobile platforms such as Android and iOS (and Windows Phone – more on that later) but has since expanded to desktop platforms such as macOS, GTK and WPF on Windows (UWP originally straddled mobile and desktop). WPF is a more recent addition to Xamarin Forms and so understandably the implementation is less mature. It does follow the native look and feel closely but I soon found quite a jarring omission.

Our app uses the ActivityIndicator to represent indeterminate activity. On Android et al. this displays a rotating circular spinner but on WPF it was using an indeterminate progress bar squashed into a rectangular space which looked odd. This is understandable as there is no native control in WPF. I then had a flash of deja vu when thinking about something I wrote some time ago for Windows Phone!

Windows Phone 8.1 introduced the WinRT application model (from Windows 8) alongside the existing Silverlight approach but there were some complications and some types of apps could only be written in Silverlight. I created a library called Charming which added some of the Windows 8 style APIs to the Silverlight app model. This was later expanded and became Pontoon. One of the APIs was a Silverlight ProgressRing control which looked just like the Windows 8 equivalent. The progress ring still regularly appears in the Windows shell and is implemented in UWP. Since Silverlight is a subset of WPF it was straightforward to port it into the Xamarin Forms WPF platform library and modify the renderer for ActivityIndicator. Voila! A nice native looking ActivityIndicator for Windows desktop apps. This has now been merged into the Xamarin Forms code and should appear in a preview release soon alongside the MediaElement that also got merged recently. Until it hits a stable release you can add it via InTheHand.Forms too.