The MIT-SHM shared memory extension was added pretty early on. And nowadays (in GTK etc.) everything is drawn on the client side and sent over as a bitmap. The

The MIT-SHM shared memory extension was added pretty early on. And nowadays (in GTK etc.) everything is drawn on the client side and sent over as a bitmap. The old-style serialized drawing commands model is only responsive when you have a very simple UI that doesn't do much drawing.