IOS core text计算文本高度及最大宽度

转自：http://lists.apple.com/archives/quartz-dev/2008/Mar/msg00079.html

 

- (CGSize) measureFrame: (CTFrameRef) frame forContext: (CGContext *) cgContext

{//frame为排版后的文本

CGPathRefframePath =CTFrameGetPath(frame);

CGRectframeRect =CGPathGetBoundingBox(framePath);

 

CFArrayReflines =CTFrameGetLines(frame);

CFIndexnumLines =CFArrayGetCount(lines);

 

CGFloatmaxWidth =0;

CGFloattextHeight =0;

 

// Now run through each line determining the maximum width of all the lines.

// We special case the last line of text. While we've got it's descent handy,

// we'll use it to calculate the typographic height of the text as well.

CFIndexlastLineIndex = numLines -1;

for(CFIndexindex =0; index < numLines; index++)

{

CGFloatascent, descent, leading, width;

CTLineRefline = (CTLineRef)CFArrayGetValueAtIndex(lines, index);

width =CTLineGetTypographicBounds(line, &ascent,  &descent, &leading);

 

if(width > maxWidth)

{

maxWidth = width;

}

 

if(index == lastLineIndex)

{

// Get the origin of the last line. We add the descent to this

// (below) to get the bottom edge of the last line of text.

CGPointlastLineOrigin;

CTFrameGetLineOrigins(frame,CFRangeMake(lastLineIndex,1), &lastLineOrigin);

 

// The height needed to draw the text is from the bottom of the last line

// to the top of the frame.

textHeight = CGRectGetMaxY(frameRect) - lastLineOrigin.y+ descent;

}

}

 

// For some text the exact typographic bounds is a fraction of a point too

// small to fit the text when it is put into a context. We go ahead and round

// the returned drawing area up to the nearest point.  This takes care of the

// discrepencies.

returnCGSizeMake(ceil(maxWidth),ceil(textHeight));

}