Universal Windows Platform (UWP) is about making it easy for app experiences to work across devices. This is a quick guide to making your 2D UWP app work great in mixed reality.
Windows 10 moves all visual design from real screen pixels to effective pixels. That means, developers design their UI following the Windows 10 Human Interface Guidelines for effective pixels, and Windows scaling ensures those effective pixels are the right size for usability across devices, resolutions, DPI, etc. See this great read on MSDN to learn more as well as this BUILD presentation.
Even with the unique ability to place apps in your world at a range of distances, TV-like viewing distances are recommended to produce the best readability and interaction with gaze/gesture. Because of that, a virtual slate in the Mixed Reality Home will display your flat UWP view at:
1280x720, 150%DPI (853x480 effective pixels)
This resolution has several advantages:
The app model for mixed reality is designed to use the Mixed Reality Home, where many apps live together. Think of this as the mixed reality equivalent of the desktop, where you run many 2D apps at once. This has implications on app life cycle, Tiles, and other key features of your app.
2D views are decorated with a app bar above their content. The app bar has two points of app-specific personalization:
Title: displays the displayname of the Tile associated with the app instance
Back Button: raises the BackRequested event when pressed. Back Button visibility is controlled by SystemNavigationManager.AppViewBackButtonVisibility.
It is important to test your app to make sure the text is readable, the buttons are targetable, and the overall app looks correct. You can test on a desktop headset, a HoloLens, an emulator, or a touch device with resolution set to 1280x720 @150%.