How to change origin of coordinates in SFML?

Question

C++ / C#

How to make the SFML starting point not from the upper left corner, but from the center of the bottom of the window? So that SetPosition(0, 0) would set the shape not to the upper left corner, but to the bottom center of the window. So that with a window width of 800, the edges would be -400 and 400 pixels.