Everything is fine under MS-Windows, but :

Is it possible to do hide minimize, maximize andclose buttonon Mac OS ?

I found NSMiniaturizableWindowMaskbut I don't know how to access system API under Mac OS

Remark under windows : WS_MINIMIZEBOX and WS_MAXIMIZEBOX can't work separately

simplified working code is (must have hwnd handle, constant and win32 method declaration) :

style = GetWindowLong.call(hwnd, GWL_STYLE)
style = style & ~WS_MINIMIZEBOX
style = style & ~WS_MAXIMIZEBOX
result = SetWindowLong.call(hwnd, GWL_STYLE,  style)

Thanks for any answer.

Philippe