Will Windows 8 Metro apps require any change to the code in order to work on ARM based devices?

Question

As far as I understand the Metro part of the runtime is not x86 processor architecture and native code dependant and will work without any change to the code on say an x86 tablet or ARM tablet. Is this correct?

Also how easy would it be to port apps from Windows Phone metro to Windows 8 metro? Can we hope that no change to code at all is a possibility?

Similarly, what about XBOX? Is there any chance Windows 8/Windows Phone metro apps can be easily ported to the new XBOX metro environment?

Answer 1

Windows 8 has something of a split personality, with the architecture shown below:

The left hand side is the newer metro-style / WinRT architecture, whilst the right-hand side is the older Win32 / .NET architecture. It has been widely reported that ARM tablets will only support the Metro / WinRT architecture. There has been no indication that ARM devices will require different code, and this seems quite unlikely based on the fact that it will have the same architecture.

Also how easy would it be to port apps from Windows Phone metro to Windows 8 metro? Can we hope that no change to code at all is a possibility?

It is slightly easier to port WP7 apps to Win8 due to the similarities in their architecture, i.e. a similar application lifecycle and a similar restricted set of APIs. However, there certainly are code changes required, see this article which presents a simple cross-platform Win8-WinRT / Silverlight application. The XAML UI elements are in different namespaces, which has an impact on all of your UI code, the XAML namespace mapping syntax is different, so you cannot share XAML. It is a bit of a mess really.

There are rumours that WP8 will use the same WinRT architecture, which would make code sharing possible. However, I think this is highly unlikely, Microsoft already introduced significant architectural changes from WP6.5 to WP7, doing it again would alienate developers.