Function set_screen_layout 

pub fn set_screen_layout(
    socket_path: &str,
    rects: Vec<(i32, i32, i32, i32)>,
) -> Result<usize, String>

Position the session’s screens at rects, one (x, y, width, height) per screen in screen order; sizes are validated but not applied, because a nested KWin screen’s size follows its host window. The rectangles are capture pixels and the positions land in the session’s logical space, closed up around each screen’s scale (outclient::close_gaps). Returns how many were positioned; 0 when the compositor serves no kde_output_management_v2.