You mean the underlying Inkscape mockup? Not sure. I've read it to become part of the official HIG for Luna+1, but there were still some issues to be solved and I'm not even sure if elementary core developers are fine with that vision.
Creo que sería bastante bueno una clase de combinación entre la maqueta previa a ésta y la segunda de arriba a abajo de ésta; en si, una clase de modal dialog pero con el resto de la ventana en gris, o al menos lo que este debajo de la decoración.
Yeah, it seems like it ought to just be consistent with other modal dialogs. The topleft position is familiar from menubars, but as something that's keyboard-driven and by nature interrupts other interaction with the window, it makes the most sense just to float it at the center of the window.
The close button might be redundant if clicking outside the box exits the search anyway, though. What happens when a user clicks outside the box?