CoreText - Bold, Italic and CTFontCreateCopyWithSymbolicTraits

[build 0047] The text publishing is slowly falling into place. I have managed to get to the bottom of most of the positioning problems. The side-by-side comparison shows publishing under OSX text is quite similar. The vertical positioning is a little different. Also under OSX the text is kerned - something that fell out from using Core Text.
More complex example (an unpleasent combination of styling) is also close.

There seems to be a bug that means that a small section of underline is missing - but more obviously some characters are not italic.

The lack of itallics is due to the way that Core Text handles fonts within a font family. A true italic font is actually a seperate font that has been designed and created specificaly by the font foudry, as is a bold version of a font. If you ask for the bold or italic form of a font (CTFontCreateCopyWithSymbolicTraits and friends) Core Text will look for an approriate font in the family - if there is not one it will fail. This is typographically the correct thing to do.

Many programs will synthesize an italic font by slanting the regular font - this works but looks a little ropey. This is what the PC version does. It is also posible to synthesize bold forms of a font. This is done by out setting the contours of each glyph. If a synthesized italic font is a bit ropey a synthesized bold tends to be a bit ugly. It is quite possible to do both in Core Text but I currenty do not plan to do it.