[cairo] How to render 1bpp bitmaps normally & selected (in GTK+ 3)

[Bill Spitzak]

>> 1. You mention the XOR operator. I never could get it to work (OpenSuSE 11.4
>> 32-bit/Gtk+ 3.0.10/cairo 1.10.2) and never managed to dig up any examples
>> that did. The DIFFERENCE operator worked exactly as advertised, but it
>> wasn't quite what I was looking for. Before I dig into the cairo sources,
>> any pointers to XOR examples that work?

XOR is between the *alpha* of the two surfaces, not the colors or the 
bits of the colors. Probably useless in this case because I would expect 
that at least the destination window has 100% solid alpha. If one of the 
items is solid alpha then XOR is going to be equivalent to some other 
operator.