demo code :
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
// Flip the coordinate system
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, 0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
NSDictionary *attrs = @{NSFontAttributeName: [UIFont systemFontOfSize:20],
NSForegroundColorAttributeName: [UIColor blueColor],
NSUnderlineStyleAttributeName: @(NSUnderlineStyleThick),
};
// Make an attributed string
NSAttributedString *attributedString = [[NSAttributedString alloc] initWithString:@"Hello CoreText!" attributes:attrs];
CFAttributedStringRef attributedStringRef = (__bridge CFAttributedStringRef)attributedString;
// Simple CoreText with CTFrameDraw
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attributedStringRef);
CGPathRef path = CGPathCreateWithRect(self.bounds,NULL);
CTFrameRef frame = CTFramesetterCreateFrame(framesetter,CFRangeMake(0, 0),path,NULL);
//CTFrameDraw(frame, context);
// You can comment the line 'CTFrameDraw' and use the following lines
// draw with CTLineDraw
CFArrayRef lines = CTFrameGetLines(frame);
CGPoint lineOrigins[CFArrayGetCount(lines)];
CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), lineOrigins);
for (int i = 0; i < CFArrayGetCount(lines); i++) {
CTLineRef line = CFArrayGetValueAtIndex(lines, i);
CGContextSetTextPosition(context, lineOrigins[i].x, lineOrigins[i].y);
// CTLineDraw(line, context);
// You can comment the line 'CTLineDraw' and use the following lines
// draw with CTRunDraw
// use CTRunDraw will lost some attributes like NSUnderlineStyleAttributeName,
// so you need draw it by yourself
CFArrayRef runs = CTLineGetGlyphRuns(line);
for (int j = 0; j < CFArrayGetCount(runs); j++) {
CTRunRef run = CFArrayGetValueAtIndex(runs, j);
CTRunDraw(run, context, CFRangeMake(0, 0));
}
}
}
this code will use CTRunDraw to draw the content , and the underline will draw and show normally in iOS17 & Xcode 15 , But when you build it with XCode16 & iOS18 beta . the underline will be missing .
