Linux: black border to the right when resizing "full screen"

When I double click the top window frame, the windows get resized to the full screen size, with a black border ONLY to its right with the latest ubuntu.
How can I get the black border to be both side?
I tried like this:

and with SDL_WINDOWSPOS_CENTERED instead of the two SDL_WINDOWPOS_UNDEFINED but the border is only to the right side.
Any idea how to fix this?