Black bars around content

[Koranir]

As shown in the image, there are black borders around the content of the window.
I think it could be fixed by centring the content and applying the nearest text background colour to the empty space (which is what I think the other terminals do).

Also, a wrong font is being used somewhere which results in the line height being larger than the full-height line character, resulting in there being gaps in helix's borders.