iphone - CTFrameGetLineOrigins 中的错误？

Question

我正在使用 Apple 的 SimpleTextInput 示例中的以下代码来确定光标的框架。我正在使用 CTFrameGetLineOrigins，我注意到它返回的 y 值不正确(无论在哪一行，它都显示 .336)。我的应用程序与 SimpleTextInput 略有不同，因为我将文本垂直居中，因此文本框架不会直接从原点开始。但是，为什么它给我每一行的值(value)？这是错误吗？

for (int i = 0; i < [lines count]; i++) 
{
    CTLineRef line = (CTLineRef) [lines objectAtIndex:i];
    CFRange range = CTLineGetStringRange(line);
    NSInteger localIndex = index - range.location;

    if (localIndex >= 0 && localIndex <= range.length) 
    {
        CGPoint origin;
        CGFloat ascent, descent;
        CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
        CTFrameGetLineOrigins(self.textFrame, CFRangeMake(i, 0), &origin);
        CGFloat xPos = origin.x + CTLineGetOffsetForStringIndex(line, index, NULL);
        return CGRectMake(xPos, origin.y - descent, 3, ascent + descent);
    }
}

- (void) drawRect:(CGRect)rect
{
    CTFramesetterRef textFramesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)self.text);
    CGMutablePathRef textFrameMutablePath = CGPathCreateMutable();
    CGPathAddRect(textFrameMutablePath, NULL, self.bounds);
    self.textFrame = CTFramesetterCreateFrame(textFramesetter, CFRangeMake(0, 0), textFrameMutablePath, NULL);

    CGFloat textFrameHeight = [self calculateHeightForTextFrame];
    CGRect textFrameRect = CGRectMake(0, (self.bounds.size.height / 2) - (textFrameHeight / 2), self.bounds.size.width, textFrameHeight);

    CGPathRelease(textFrameMutablePath);
    textFrameMutablePath = NULL;

    CFRelease(self.textFrame);
    self.textFrame = NULL;

    textFrameMutablePath = CGPathCreateMutable();
    CGPathAddRect(textFrameMutablePath, NULL, textFrameRect);
    self.textFrame = CTFramesetterCreateFrame(textFramesetter, CFRangeMake(0, 0), textFrameMutablePath, NULL);

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    CGContextTranslateCTM(context, 0, self.bounds.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    CTFrameDraw(self.textFrame, context); 

    CGPathRelease(textFrameMutablePath);
    CFRelease(textFramesetter);

    [self cursorPositionChanged];
}

Answer 1

Take out CTFrameGetLineOrigins() out of loop to get all line origins like :

NSArray *lines = (__bridge id)CTFrameGetLines(frame);
CGPoint origins[lines.count];
CTFrameGetLineOrigins(frame, CFRangeMake(0, lines.count), origins); //this will fill all line origins in origins[] buffer.

for (int i = 0; i < [lines count]; i++)
{
    CTLineRef line = (__bridge CTLineRef) [lines objectAtIndex:i];
    CFRange range = CTLineGetStringRange(line);

    // CGPoint origin; // moved out of loop
    CGFloat ascent, descent;
    CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
    // CTFrameGetLineOrigins(frame, CFRangeMake(i, 1), &origin); // moved to out of loop
    CGFloat xPos = origins[i].x; //  + CTLineGetOffsetForStringIndex(line, index, NULL);
    NSLog(@"%@", NSStringFromCGRect(CGRectMake(xPos + origins[i].x, origins[i].y - descent, 3, ascent + descent)));
}