Well, this question has not much to do with ScreenSpace, but in fact how up-scaling is implemented in WP7.

If you set preferedBackBuffer.Width to 300 in your XNA game (or do it pretty much the same way with Settings.Resolution = new Size(300, 200) via the Delta Engine), your game will actually use 300 pixels in PixelSpace. No pixel beyond that will be rendered. Your GraphicsDevice.Viewport is just used to tell the device where to render your back-buffer (it could even just be half your screen or whatever else region you want to paint, usually it will cover the whole device to do the up-scaling).

So the pixelspace is your prefered back buffer size (or Settings.Resolution in DE) and not the up-scaling size of your device, which is Graphics.Viewport by default if you have not changed it (or Application.Information.MaxResolution in DE).

See: http://msdn.microsoft.co...us/library/ff966425.aspx

Checkout the wiki page about Quadratic Screen Space to understand it better: http://deltaengine.net/Wiki.ScreenSpace

The basic idea is to get rid of resolutions and aspect ratios and keep all applications and games inside the (0-1) range for both width and height. Obviously everything would look stretched and wrong, so either top and bottom (for widescreen or landscape mode) will be cropped or left and right (for portrait mode) will be cropped.

This means you should not use the full (0-1) range in your game, but instead some inner area that is always available. You can still dock stuff at the screen borders via Screen.DrawArea (which tells you where the border is in quadratic space).

Use the ScreenSpace.ToQuadraticSpace and ToPixelSpace helper methods to convert from one space to another. Since this functionality is not in XNA it won't be that easy to port it outside of the Delta Engine ^^