private int GET_Y_LPARAM( LONG_PTR lParam ) {
			return (short) ((lParam.longValue() >> 16) & 0xffff);
		}
Same implementation as GET_Y_LPARAM(lp) macro in windowsx.h.
Y-coordinate is in the high-order short and may be negative.

https://docs.microsoft.com/en-us/windows/win32/inputdev/wm-nchittest#remarks
flatlaf-natives/flatlaf-natives-jna/src/main/java/com/formdev/flatlaf/natives/jna/windows/FlatWindowsNativeWindowBorder.java