What are the limitations of scaling to multiple resolutions on WP7

Question

I 'am developing an app targeted to WP7.1 but I want it to work well on WP8 devices too. Assuming creating layout using dynamic resizng elements (grids with auto height etc) will the app scale just like WP8 app under Windows Phone 8 (WP8 handles WVGA HD WXGA resolutions)? If yes, is this possible to get a exact screen size under WP7 and what about in-app images in high resolution? If not, should I build 2 different apps to handle scaling well? One for WP7 and another for WP8 (even if the only change is build target?)

Answer 1

WP7 only supports 800x480 resolution and will automatically scale on WP8.

WP7 app cannot however do any resolution dependant tweaks when app runs on WP8. You need to recompile it to WP8