ios - 如何找到包含给定字符的字体？

Question

我有一种用于我的应用程序的字体，它只使用英文字符。我使用 CoreText 来显示文本，我注意到每当有人输入字体中未包含的字符(如阿拉伯字符)时，程序就会卡在这一行:

CTFramesetterCreateFrame(textFramesetter, CFRangeMake(0, 0), textMutablePath, NULL); 

我有几个问题:

1. 是否可以知道某个字符是否包含在字体中？
2. 系统能否找到包含未知字符的字体？

相关:Check if certain character is supported by UIFont

Answer 1

1) 是否可以知道字体中是否包含某个字符？

BOOL FontContainsCharacter(UIFont *font, unichar character) {
    NSCharacterSet *characterSet = [font.fontDescriptor objectForKey:UIFontDescriptorCharacterSetAttribute];
    return [characterSet characterIsMember:character];
}

2) 系统是否可以找到包含未知字符的字体？

NSArray *FontDescriptorsForFontsContainingCharactersInString(NSString *string) {
    NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:string];
    NSDictionary *fontAttributes = @{UIFontDescriptorCharacterSetAttribute:characterSet};
    UIFontDescriptor *fontDescriptor = [UIFontDescriptor fontDescriptorWithFontAttributes:fontAttributes];
    return [fontDescriptor matchingFontDescriptorsWithMandatoryKeys:nil];
}

例如:

NSLog(@"%d", FontContainsCharacter([UIFont fontWithName:@"Helvetica" size:12], 0x0041)); // "A"
NSLog(@"%d", FontContainsCharacter([UIFont fontWithName:@"Helvetica" size:12], 0x4F60)); // "你"

for (UIFontDescriptor *fontDescriptor in FontDescriptorsForFontsContainingCharactersInString(@"你好")) {
    NSLog(@"%@", [UIFont fontWithDescriptor:fontDescriptor size:12].fontName);
}

输出:

1
0
STHeitiSC-Light
STHeitiSC-Medium
STHeitiTC-Light
STHeitiTC-Medium
HiraKakuProN-W3
HiraKakuProN-W6
HiraMinProN-W3
HiraMinProN-W6