Function create_output_on 

pub(crate) fn create_output_on(
    state: &mut AppState,
    id: u32,
    width: i32,
    height: i32,
    x: i32,
    y: i32,
    scale: f64,
) -> bool

Create an additional output mapped into the layout at (x, y). Fails (false) on a duplicate id, non-positive geometry/scale, a rectangle overlapping a live output, or a GPU render-target allocation failure. Only Create/Reposition placements are validated: a capture reconfigure (StartCapture on an existing output) resizes UNVALIDATED, so keeping a multi-step relayout overlap-free at every step is the caller’s ordering responsibility.