With the recent addition of the libxpresent, it should improve frame
timings for most users. However, there were known cases of bad behavior
(Nvidia) which lead to a construction of a whitelist instead of just
enabling this all the time. Since there's no way to predict whatever
combination of hardware/drivers/etc. may work correctly, just give users
an option to switch the usage of xorg's presentation statistics on/off.
The default value, auto, works like before (basically, Mesa drivers and
no Nvidia are allowed), but now one can force it on/off if needed.
Dudemanguy
24f4582b6f