Preview Composition is your first stop for testing. It displays your compositions as they would appear in the app without the need for devices and build scripts. This greatly accelerates the testing process, allowing you to try multiple iterations of your project in a short amount of time and without developer assistance.
One of the biggest advantages of using You.i Engine is that one project file can be used for multiple devices. Preview Composition allows you to quickly test your project file on any screen size without the need for a physical device to export to. You can also simulate dynamic content to see how your layout will hold up in any situation.
Select You.i: Preview Current Composition from the Composition menu to access this feature. The current composition is then displayed in a top level window with an application menu.
The features of the preview app are arranged under three menus: Animation, Content and Screen.
The preview feature is intended primarily for compositions that will function as screens, that is, ones that will fill the whole target device screen at run time, rather than those that are elements of screens like lists and buttons. The Screen menu contains screen profiles representing the most popular mobile and 10 foot resolutions and allow you to see quickly how the current composition will look on them. Initially the composition will be displayed at a size equal to its size in AE and if that matches a known screen profile that will be indicated. You can also easily switch between portrait and landscape orientations.
The Animation menu provides options for playing default screen oriented timelines (In, Out, etc) as well as selecting and playing custom timelines.
The Content menu provides options for dynamically setting the text and the font size of text layers. It also provides options for displaying various backgrounds, grids, outlines and overlays to help you visualize your composition.