I have this layout engine, which works on the standard TeX-like principle: text is in boxes and sent to a shaper, spaces are intercepted and replaced by flexible glue nodes, on the assumption that a font's space width is constant.
SIL's Awami font makes heavy use of space kerning, and so breaks that assumption. It expects text including spaces to be sent to the shaper, which will return a kerned (context-sensitive) space width. I could make this happen but it makes line breaking much more complex as I will need to look into and break up shaped text runs.
I don't really like the idea of changing the shaping system for one font, but I might need to if my assumptions about how layout works are incorrect.
i seem to remember a recent discussion somewhere about this sort of thing in the context of OpenType Layout, but I can't put my hands on it right now.
So some questions:
Is this kind of space kerning "a thing" that I need to worry about?
Does it affect other systems than Nastaliq?
Should I stop intercepting spaces and move to a "shape everything" model?