I have code that lays out text on a path. It essentially boils down to
the technique given in the Text Layout Programming Guide example code
(Circle text) of setting up a transform before letting the layout
manager get on with its normal work, done by calling -[NSLayoutManager
drawGlyphsForGlyphRange:atPoint:]; where the point is calculated from
the -locationOfGlyphAtIndex: method (each glyph has to be drawn
individually for obvious reasons, so the glyph range is always length 1)
This works great for almost everything you can do with an attributed
string, but doesn't handle superscripts properly. Any super- or
subscripted glyph always ends up on the baseline.
I have tried two things so far:
a) ask the typesetter, using -[NSTypesetter
baselineOffsetInLayoutManager:glyphIndex:];
That produces nothing different for the superscripted characters.
b) going back to the original string's superscript attribute. That
could work, since I have complete control over the baseline for each
character. However, the superscript attribute is an integer which I
understand to mean n units of "superscriptness" in proportion to h,
where h is ??? lineheight? font height? I can't find any information
on how this value can be turned into a baseline position.
So that would be good to know if anyone can help. That still leaves me
mystified as to why the layout manager doesn't "just work" though.
--Graham
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