How are you getting the characters onto the screen? Eg: one big dynamic mesh with a quad per character, or a dynamic texture with one texel representing each character, or a software renderer to a dynamic texture, or a whole lotta sprites (IDK what interfaces SDL provides) or?
One quirk of this is that I haven't put a padding line between the rows. This means it's not 1:1 perfect with a standard terminal but... I think I prefer this look?