add_cross_hair( fig )

This tool enables easily add/remove a mouse following cross-line.

I found this tool especially useful when you want to compare 2 curves in 2 subplots. Just at command line input add_cross_hair then you will see a mouse following cross-line in x and y direction covering whole figure canvas.
To use other figure tools (such as zoom and pan tools), press 'space' on your keyboard and you temporarily toggle off this mouse function. When you press 'space' again, you will get the lovely lines again.

To totally remove this mouse following function for your current figures 'WindowButtonMotionFcn' function, just press 'esc' on your keyboard.

Hope you enjoy the function.

Chen