attachement 5572 (in bug 690855) shows artifects with x11alpha. x11 is correct.
Created attachment 5586 [details] x11alpha screen grab screen grab.
the file appears to be gray version of same thing, and since x11alpha is x11 with -dGraphicsAlphaBits=4 set, this is probably same bug as 691181
This appears to be fix with the current head. See attached image of x11alpha vs x11 output.
Created attachment 16825 [details] compare Comparison of x11 vs x11alpha with head