[API Proposal] System.Windows.WindowStartupMonitor

In times of multi monitor setup I would like to propose a new API that allows us to set the startup monitor of the window. I am open for naming changes. The reason is that many developers would prefer to use the WindowStartupLocation.CenterScreen but only change the monitor from the monitor on which the mouse is currently located to a fixed monitor.

The way to do this ourselves is tedious. Enumerating all screens, calculating the center, use WinAPIs to move the window. `WindowStartupMonitor` could be an integer which stands for the index of the monitor. By default it could be `-1` which means "the monitor on which the mouse is currently located".

Ideas? Suggestions?

Edit: based on the discussion and all the mentioned problems this proposal has been changed to provide a way to set the startup monitor to the primary monitor (instead of the current behavior of "screen that contains the mouse cursor").

```diff
namespace System.Windows
{
public class Window
{

+ [DefaultValue(WindowStartupMonitor.Cursor)]
+ public WindowStartupMonitor WindowStartupMonitor
+ {
+ get {...}
+ set {...}
+ }

}

+ public enum WindowStartupMonitor
+ {
+ Cursor = 0,
+ Primary = 1
+ }

}


```