private int GET_X_LPARAM( LONG_PTR lParam ) {
			return (short) (lParam.longValue() & 0xffff);
		}
Same implementation as GET_X_LPARAM(lp) macro in windowsx.h.
X-coordinate is in the low-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