I think the ligature from MonoLisa is a good example of how not to do ligatures. I can't tell whether it stands for "#={" or "#{". Ligatures can be nice, to each their own, but only if they don't introduce ambiguity.
It also makes no sense and looks terrible to connect those two glyphs with a ligature.
Unlike "fi" or "ij", there's no reason (kerning or spelling) to want to smush # into {.
I don't doubt that but I cannot really pinpoint what the reason is to want "fi" and "ij" in a monospace font? Do these narrow letter ligatures then take up only a single character cell?
>Since we are working with a monospace font, every glyph must have the same advance
Just pointing out that this is merely an expectation and not a rule. You can happily design a "monospace" font in any font publishing software that blatantly disrespects a single width. In fact, you can just manually make any letterform 2x width, and that is exactly what most monospace ligatures do! (except the bad ones, which combine e.g. "fi" ligature a single width letter)
The ligature letters are just... 2x width. Believe it or not this is totally legal!
> you can just manually make any letterform 2x width,
Yes. Any glyph may be wider than its advance. The advance, however, must remain the same across all glyphs. If it does not, the font is not monospaced.
The passage you’ve quoted refers not to the width, but to the advance.
Fonts are kind of dumb. There's usually nothing actually weird going on. Ligatures are simple character substitutions. What the LIGSPACE is, most likely, is a spacing character added by the designer to align the characters in the ligature correctly. So, the LIGSPACE is just a character like any other and is nothing special. For example, when you hit a space bar, you are inserting a character which doesn't render anything because the designer didn't draw anything there. There's no extra logic.
Just pointing out that this is merely an expectation and not a rule. You can happily design a "monospace" font in any font publishing software that blatantly disrespects a single width. In fact, you can just manually make any letterform 2x width, and that is exactly what most monospace ligatures do! (except the bad ones, which combine e.g. "fi" ligature a single width letter)
The ligature letters are just... 2x width. Believe it or not this is totally legal!
https://www.hanselman.com/blog/monospaced-programming-fonts-...
> you can just manually make any letterform 2x width,
Yes. Any glyph may be wider than its advance. The advance, however, must remain the same across all glyphs. If it does not, the font is not monospaced.
The passage you’ve quoted refers not to the width, but to the advance.