Disabling the fullscreen editing view for soft keyboard input in landscape?

I finally answered my own question:

The extract UI (i.e. the fullscreen editing mode) can be disabled at the point at which the input connection is hooked up:

@Override
public InputConnection onCreateInputConnection(EditorInfo outAttrs) {

    outAttrs.imeOptions = EditorInfo.IME_FLAG_NO_EXTRACT_UI;

    // etc.
}