Originally, the font graphics were supposed to use colored backgrounds to identify the width of each glyph. I'm not sure whether this was removed or just never implemented.
rsfont will need to support this behavior as well.
static const u8 sFont0Widths[] =
{
3, 6, 6, 6, 6, 6, 6, 6, 6, 6, 8, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 8, 6, 6, 6, 6, 6, 4, 8,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 8, 6, 6, 8,
8, 8, 8, 8, 8, 8, 3, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
7, 6, 4, 8, 8, 8, 7, 8, 8, 4, 6, 6, 4, 4, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 6, 7, 8, 7, 7, 8, 8, 4,
7, 8, 8, 8, 8, 8, 7, 8, 7, 7, 7, 7, 7, 7, 8, 7,
7, 7, 7, 7, 5, 6, 6, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
8, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 3, 6, 3, 5, 3,
6, 6, 6, 3, 3, 6, 6, 6, 3, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 5, 6,
3, 6, 6, 6, 6, 6, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7,
3, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 1, 1,
};