CTFontGetGlyphsForCharacters始终返回false

问题描述

请使用以下代码帮助我理解问题:

Please help me understand the problem with the following code:

NSString *fontName = @"ArialMT";
CGFloat fontSize = 20.0;
CTFontRef fontRef = CTFontCreateWithName((CFStringRef)fontName, fontSize, NULL);
NSString *characters = @"ABC";
NSUInteger count = characters.length;
CGGlyph glyphs[count];
if (CTFontGetGlyphsForCharacters(fontRef, (const unichar*)[characters cStringUsingEncoding:NSUTF8StringEncoding], glyphs, count) == false)
    NSLog(@"*** CTFontGetGlyphsForCharacters failed.");

感谢您的帮助.

推荐答案

您将获得一个包含UTF-8编码字符的C字符串，然后将其强制转换为 unichar * .那行不通. unichar 是16位UTF-16编码的字符.简单的C强制转换不会转换字符编码.

You are getting a C string containing UTF-8 encoded characters and then casting it to unichar *. That won't work. A unichar is a 16-bit UTF-16-encoded character. A simple C cast won't convert the character encoding.

您需要以 unichar 的数组的形式询问字符串的字符:

You need to ask the string for its characters as an array of unichar:

NSString *fontName = @"ArialMT";
CGFloat fontSize = 20.0;
CTFontRef fontRef = CTFontCreateWithName((CFStringRef)fontName, fontSize, NULL);
NSString *string = @"ABC";
NSUInteger count = string.length;
unichar characters[count];
[string getCharacters:characters range:NSMakeRange(0, count)];
CGGlyph glyphs[count];
if (CTFontGetGlyphsForCharacters(fontRef, characters, glyphs, count) == false)
    NSLog(@"*** CTFontGetGlyphsForCharacters failed.");

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