WHAT’S NEW IN WINDOWS 8.1
Windows 8.1 adds the ability to resize applications, replacing “snapping” an application into SnapView from Windows 8.0. Applications can have a minimum size of 500 pixels (px; the default) or 320 px.
Due to this change in the UI, a significant change in Windows 8.1 is the deprecation of ApplicationViewState. ApplicationViewState is utilized by the LayoutAwarePage, and the LayoutAwarePage base class is used in all Windows 8.0 templates and the Basic Page. Therefore, any applications that use a LayoutAwarePage will break.
Determining layout decisions now utilizes the ApplicationView properties, as shown ...