error: cannot convert 'tyObject_XEvent__EZvRvOUywFnBp4PzilZBoA' to 'XEvent&'

[sls1005]

You can just convert the arguments when calling.
    
    
    proc processMessage*(this: var XwWindow; theListener: var 
AIS_ViewController;
                        theMsg: var XEvent): bool {.cdecl, importcpp: 
"#.ProcessMessage(('2) #, ('3) #)".}
    
    
    Run