[cairo] How to exactly overwrite anti-aliased shapes?

[Lawrence D'Oliveiro]

On Fri, 16 Sep 2016 08:55:28 -0400, Josh Sanford wrote:

> It doesn't make intuitive sense to me that overwriting the very same
> shape would not overwrite all of its pixels, especially if I force it
> into non-blending CAIRO_OPERATOR_SOURCE mode.

Anti-aliasing involves blending. If you don’t want anti-aliasing, turn
it off.

Of course, the correct answer to your situation is to keep a complete
copy of the destination pixels from before you drew the new shape, and
start the drawing again from that.