Keys reach a game under Wine on Xvfb only with a window manager running

Symptoms

On a headless X server (Xvfb), the mouse works in the game but keys do nothing. Keys sent with xdotool reach the window. The game ignores them.

Cause

With no window manager, no window becomes the foreground window. A DirectInput device with foreground cooperation then stays unacquired, so the game reads no keys (observed: keys moved the menu highlight only after a window manager ran).

What to do

Start a small window manager on the display before the game: openbox & (or any other). Wine's virtual desktop (explorer /desktop=) does not replace it. On Xvfb under Wine 10 it gave a black desktop of the wrong size.

Tried

• Wine's virtual desktop on Xvfb: a black desktop of the wrong size.