iphone - Core Text/NSStringDrawing - CFAttributedStringRef/NSAttributedString - 更改字体大小

Question

案例:属性字符串已创建。如何改变字符串的大小？

我猜我们可以

A) 更新属性字符串中所有字体的 pointSize

B)通过一些变换绘制属性字符串

Answer 1

我已经用下面的代码让它工作了。但有一个问题是，如果属性字符串中的某些文本尚未设置字体属性，则它将不会更新。所以我必须用字体属性封装所有内容。

- (void)recalculateSizeChangeInAttributedString {

    if(self.attributedStringOriginal == nil) {
        self.attributedStringOriginal = [self.attributedString copy];
    }

    CFMutableAttributedStringRef tempString = CFAttributedStringCreateMutableCopy(CFAllocatorGetDefault(), self.attributedStringOriginal.length, (CFMutableAttributedStringRef)self.attributedStringOriginal);

    int lastIndex = 0;
    int limit = CFAttributedStringGetLength(tempString);
    for (int index = 0; index < limit;) {

        CFRange inRange = CFRangeMake(0, limit - index);
        CFRange longestEffective;
        CTFontRef font = (CTFontRef)CFAttributedStringGetAttribute(tempString, index, kCTFontAttributeName, &longestEffective);

        if(font != nil) {

            // log for testing
            NSLog(@"index: %i, range: %i - %i, longest: %i - %i, attribute: %@", 
                  index, inRange.location, 
                  inRange.location + inRange.length, 
                  longestEffective.location, longestEffective.location + longestEffective.length, 
                  @"..." 
                  );


            // alter the font and set the altered font/attribute
            int rangeEnd = longestEffective.length != 0 ? longestEffective.length : 1;
            CTFontRef modifiedFont = CTFontCreateCopyWithAttributes(font, CTFontGetSize((CTFontRef)font) * sizeFactor, NULL, NULL); 
            CFAttributedStringSetAttribute(tempString, CFRangeMake(index, rangeEnd), kCTFontAttributeName, modifiedFont); 
            CFRelease(modifiedFont);

        }

        // make next loop continue where current attribute ended
        index += longestEffective.length; 

        if(index == lastIndex)
            index ++;
        lastIndex = index;

    }

    self.attributedString = (NSMutableAttributedString *)tempString;

    CFRelease(tempString); 

 }