X had security in Solaris with B2 security extensions. By 2006 at the latest: https://en.m.wikipedia.org/wiki/Trusted_Solaris https://en.m.wikipedia.org/wiki/T

X had security in Solaris with B2 security extensions. By 2006 at the latest: https://en.m.wikipedia.org/wiki/Trusted_Solaris https://en.m.wikipedia.org/wiki/Trusted_Solaris Window tearing is a function of the drivers or some poor design decision and not intrinsic to X11.