iOS CoreText 绘制文本

import "CoreText/CoreText.h"

• (void)drawRect:(CGRect)rect {

  [super drawRect:rect];

  // 步骤 1
  CGContextRef context = UIGraphicsGetCurrentContext();

  // 步骤 2
  CGContextSetTextMatrix(context, CGAffineTransformIdentity);
  CGContextTranslateCTM(context, 0, self.bounds.size.height);
  CGContextScaleCTM(context, 1.0, -1.0);

  // 步骤 3
  CGMutablePathRef path = CGPathCreateMutable();
  CGPathAddRect(path, NULL, self.bounds);

  // 步骤 4
  NSMutableParagraphStyle * paragraphStyle = [[NSMutableParagraphStyle alloc] init];
  [paragraphStyle setLineSpacing:10];
  UIColor *color = COLOR_WHITE;
  NSAttributedString *string = [[NSAttributedString alloc] initWithString:self.string attributes:
  @{NSForegroundColorAttributeName:color,
  NSParagraphStyleAttributeName: paragraphStyle}

                              ];
  

  CTFramesetterRef framesetter =
  CTFramesetterCreateWithAttributedString((CFAttributedStringRef)string);
  CTFrameRef frame =
  CTFramesetterCreateFrame(framesetter,
  CFRangeMake(0, [string length]), path, NULL);

  // 步骤 5
  CTFrameDraw(frame, context);

  // 步骤 6
  CFRelease(frame);
  CFRelease(path);
  CFRelease(framesetter);
  }