The main problem with bitmap fonts is that SFML would need to define its own font file format (or pick a standard one, if any), that defines:
- the position and size of glyph sprites in the font texture
- the font metrics (line spacing, ...)
- the various glyphs' metrics (advance, kernel, ...)
Another solution would be to provide an empty shell, with various setters that would be called by the user to populate all the bitmap font's attributes. But then what's the point of a bitmap font class?