如何在转换的WPF控件上获得鼠标单击的坐标？

I'm playing with a simple WPF application. One part of it includes a grid containing several controls. The grid is rotated using a LayoutTransform and a RotateTransform. I need to get the co-ordinates of a mouse-click relative to the top-left of the grid, taking the rotation into account.I'm playing with a simple WPF application. One