Change the window's opacity / hide it without affecting its childs

问题

I simply have a drawing area, contained in a GtkWindow toplevel.

How can I hide the window / make it fully transparent without doing that to its children too (in that case the the drawing area) ?

I am aiming to the case in which everything drawn by the program is just the canvas drawing.

来源：https://stackoverflow.com/questions/32534734/change-the-windows-opacity-hide-it-without-affecting-its-childs