After pressing Cmd + Shift + 4, press Space and then click on a window or alert to screenshot it entirely, instead of having to drag out a rectangular region. I

After pressing Cmd + Shift + 4, press Space and then click on a window or alert to screenshot it entirely, instead of having to drag out a rectangular region. It works at the level of the compositor so the screenshot includes its chrome and translucent drop shadow, and nothing behind or overlapping the window,