These frame parameters, meaningful on all kinds of terminals, deal with which buffers have been, or should, be displayed in the frame.
onlymeans this frame is just a minibuffer. If the value is a minibuffer window (in some other frame), the frame uses that minibuffer.
This frame parameter takes effect when the frame is created, and can not be changed afterwards.
other-bufferuses this predicate (from the selected frame) to decide which buffers it should consider, if the predicate is not
nil. It calls the predicate with one argument, a buffer, once for each buffer; if the predicate returns a non-
nilvalue, it considers that buffer.
nil, this frame's window is never split automatically.