Why does Core Text return Myriad Pro Semibold when requesting a bold version of Myriad Pro

Question

I have the common Adobe Myriad Pro fonts installed. These include Myriad Pro Regular, Myriad Pro Bold and Myriad Pro Semibold. Assume that I have a CTFontRef baseFont that points to Myriad Pro Regular, and that the font size I desire is size. I run the following code:

CTFontRef boldFont = CTFontCreateCopyWithSymbolicTraits(baseFont, size, NULL, kCTFontBoldTrait, kCTFontBoldTrait);

The returned font is Myriad Pro Semibold, not Myriad Pro Bold.

Is there a way of coercing this to return Myriad Pro Bold instead, other than requesting the named style 'Bold'? I wanted to keep this code entirely generic without hard-wiring style names.

I have tried this in various permutations, including passing the bold trait as part of an attribute dictionary when I initially create my font, avoiding the two-step process described here, but it still returns the semibold font in preference to the normal bold. I've also poked around the fonts themselves a little. The full bold font has a weight of 700 in its <OS/2> table, and the semibold font has a weight of 600. The PANOSE weights correspond with this. However, the macStyle fields in the <head> table of the semibold and bold fonts both have the bold flag set, so presumably this is what Core Text is using. But is there any way to make it more discriminating?

Jim DeLaHunt Jim DeLaHunt · Accepted Answer · 2012-02-03T23:17:58

Based on a reading of the documentation, backed up by some knowledge of font handling in general but not Core Text specifically, I'd say it may be possible, but it's not straightforward.

The CTFontCreateCopyWithSymbolicTraits() documentation specifies that the symTraitValue and symTraitMask parameters have type CTFontSymbolicTraits. The CTFontDescriptor() documentation defines that "Bold" value that you are using as

kCTFontBoldTrait = (1 << 1)

So this is clearly a boolean trait. However, as you've seen, font weight is a spectrum, not a boolean trait, even though decades of "bold" buttons in word processor UIs have presented it as a boolean trait. CTFontCreateCopyWithSymbolicTraits() doesn't have the expressive power you need.

One other approach which might work is to try calling CTFontDescriptorCreateMatchingFontDescriptors(). You pass this function a CTFontDescriptorRef to an initial font, and a CFSetRef with attributes which must be present. This function returns an array of font descriptors, all of which match the attributes you requested.

So, you could pass it a CTFontDescriptorRef for Myriad Pro Regular, and maybe a CFSetRef saying you want bold, and then look through every font descriptor in the returned array to find the one with the heaviest weight.

I haven't written this code, and my ignorance of Core Text means I may be missing something, but that seems like a plausible approach.

Why does Core Text return Myriad Pro Semibold when requesting a bold version of Myriad Pro

2 Answers