Sets window to be embedded in embedder.
To fully embed an offscreen window, in addition to calling this
function, it is also necessary to handle the "pick-embedded-child"
signal on the embedder and the "to-embedder" and
"from-embedder" signals on window.
Since 2.18
Sets window to be embedded in embedder. To fully embed an offscreen window, in addition to calling this function, it is also necessary to handle the "pick-embedded-child" signal on the embedder and the "to-embedder" and "from-embedder" signals on window. Since 2.18