PresentPixmap mode copy tears the screen
If I understand correctly, the copy mode is a fallback mode if pageflip failed in the driver, or the driver doesn't implement flip at all, which looks fine.
But I did some experiment with Present myself, and according to my observation, tearing still happens when the pixmap is presented using the Copy mode.
I have experienced this in two different drivers: NVIDIA proprietary, which presumably doesn't implement Present; and modeset, because its page flip fails with an error message (see #68 (closed)).
Since Copy is a fallback mode, I don't know if it just isn't expected to prevent tearing.