Function apply_layout 

fn apply_layout(
    conn: &Connection,
    queue: &mut EventQueue<CtrlState>,
    state: &mut CtrlState,
    qh: &QueueHandle<CtrlState>,
    slots: &[LayoutSlot],
) -> bool

Ask the host (wlr-output-management) to give every active output its wanted mode and layout position in one atomic configuration. Retries across a canceled (stale serial). Returns whether the host said it applied the layout: false for a refusal, no answer by LAYOUT_DEADLINE, or no manager at all (KWin offers only its own kde_output_management protocol). Either answer settles the request, and the session owner then re-sizes its capture to the mode the host announces, so capture follows the host instead of gating forever on a size it will never produce.