CoreText - flipped coordinates and glyph curves.

Text output is requires partial fonts to be included in the file format. This is done by having the glyph outlines embedded in the file. As described earlier I am using Core Text to get the glyph outlines (see). Unfortunately (looking at the output) the outlines are flipped.

This particular problem is caused by CoreGraphics (Quartz) having a flipped y-axis, so zero is at the bottom rather that the top. This can be corrected by passing an appropriate transform (flipping allong the baseline) through to CTFontCreatePathForGlyph. This snippet calculates an appropriate flipped transform.

sFlipTransform = CGAffineTransformIdentity;
sFlipTransform = CGAffineTransformScale
(sFlipTransform, 1, -1);

Which results in the glyphs being correctly orientated.