Function XPLMGetWindowGeometryOS 

pub unsafe extern "C" fn XPLMGetWindowGeometryOS(
    inWindowID: XPLMWindowID,
    outLeft: *mut c_int,
    outTop: *mut c_int,
    outRight: *mut c_int,
    outBottom: *mut c_int,
)

XPLMGetWindowGeometryOS

This routine returns the position and size of a “popped out” window (i.e., a window whose positioning mode is xplm_WindowPopOut), in operating system pixels. Pass NULL to not receive any parameter.