Subtitle x / y "-1" value is not working.

[Uzver123]

Setting x / y to -1 does nothing meaningful.

From subtitle() help page:
x, y Text position. Can be set to -1 to automatically center the text horizontally or vertically, respectively.

[pinterf]

Thanks for the report, using -1 for centering is longer a valid option since fixing issue #293.
Documentations will be corrected accordingly; in general the Subtitle doc part must be refreshed, there are new parameters in 3.7.3 as well: bold, italic and noaa.