CoreText: Invalid 'kern' Subtable In CTFont

Question

I am using a custom font applied to a CATextLayer. I am using the tutorial and sample code found here. http://www.freetimestudios.com/2010/09/13/custom-fonts-on-the-ipad-and-ios-4/

However, every so often, I get the following error. Nothing in particular seems to trigger it. Can someone shed some light as to what this means? What to check for?

CoreText: Invalid 'kern' Subtable In CTFont <name: Intellect, size: 20.000000, matrix: 0x0>
CTFontDescriptor <attributes: <CFDictionary 0xac07a80 [0x38295d98]>{type = mutable, count = 1, capacity = 3, pairs = (
    0 : <CFString 0x3833f750 [0x38295d98]>{contents = "NSFontNameAttribute"} = <CFString 0x159af0 [0x38295d98]>{contents = "Intellect"}

I load the font using the following code. This code is taken from the project in the link above.

- (CTFontRef)newCustomFontWithName:(NSString *)fontName
                            ofType:(NSString *)type
                        attributes:(NSDictionary *)attributes
{
    NSString *fontPath = [[NSBundle mainBundle] pathForResource:fontName ofType:type];

    NSData *data = [[NSData alloc] initWithContentsOfFile:fontPath];
    CGDataProviderRef fontProvider = CGDataProviderCreateWithCFData((CFDataRef)data);
    [data release];

    CGFontRef cgFont = CGFontCreateWithDataProvider(fontProvider);
    CGDataProviderRelease(fontProvider);

    CTFontDescriptorRef fontDescriptor = CTFontDescriptorCreateWithAttributes((CFDictionaryRef)attributes);
    CTFontRef font = CTFontCreateWithGraphicsFont(cgFont, 0, NULL, fontDescriptor);
    CFRelease(fontDescriptor);
    CGFontRelease(cgFont);
    return font;
}

Answer 1

I had the same problem and the solution was that I was using the wrong subset. I initially downloaded Open Sans from Google Fonts which caused the same error as above. I downloaded Open Sans from Font Squirrel using the MacRoman subset and that fixed my error.

Answer 2

Validating the installed font showed there was a problem with the fonts "kern" values. This was what was causing the problem.