NSString boundingRectWithSize cutting height short with CoreText Framesetter ? iOS

NSString boundingRectWithSize cutting height short with CoreText
Framesetter ? iOS

I have a custom UIView which is drawing an NSString via CoreText :
- (NSMutableAttributedString *)getAttributedString : (NSString
*)displayText {
string = [[NSMutableAttributedString alloc]
initWithString:displayText];
helvetica = CTFontCreateWithName(CFSTR("Helvetica"), 20.0, NULL);
[string addAttribute:(id)kCTFontAttributeName
value:(__bridge id)helvetica
range:NSMakeRange(0, [string length])];
return string;
}
- (void)drawRect:(CGRect)rect
{
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(
(__bridge
CFAttributedStringRef)string);
// left column form
leftColumnPath = CGPathCreateMutable();
CGPathAddRect(leftColumnPath, NULL,
CGRectMake(0, 0,
self.bounds.size.width,
self.bounds.size.height));
// left column frame
textleftFrame = CTFramesetterCreateFrame(framesetter,
CFRangeMake(0, 0),
leftColumnPath, NULL);
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
// right column form
rightColumnPath = CGPathCreateMutable();
CGPathAddRect(rightColumnPath, NULL,
CGRectMake(self.bounds.size.width/2.0, 0,
self.bounds.size.width/2.0,
self.bounds.size.height));
NSInteger rightColumStart =
CTFrameGetVisibleStringRange(textleftFrame).length;
// right column frame
textrightFrame = CTFramesetterCreateFrame(framesetter,
CFRangeMake(rightColumStart, 0),
rightColumnPath,
NULL);
}
// flip the coordinate system
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, 0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// draw
CTFrameDraw(textleftFrame, context);
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
CTFrameDraw(textrightFrame, context);
}
// cleanup
CFRelease(textleftFrame);
CGPathRelease(leftColumnPath);
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
CFRelease(textrightFrame);
CGPathRelease(rightColumnPath);
}
CFRelease(framesetter);
CFRelease(helvetica);
CFRelease(helveticaBold);
}
In another class I am then trying to use boundingRectWithSize to calculate
how long the view will be to display the text (I then later set a
UIScrollView to match this) :
NSMutableAttributedString * attributedString = [textView
getAttributedString:text];
// Code here for iOS 7.0 - sizeWithFont is deprecated.
CGRect textBoxSize = [attributedString
boundingRectWithSize:CGSizeMake(315.f, CGFLOAT_MAX) options:
(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
context:nil];
textView.frame = CGRectMake(textView.frame.origin.x, pictureSpace,
textBoxSize.size.width, textBoxSize.size.height);
The getAttributedString method is above. The problem is that textView is
slightly too short in height and therefore cuts off the last line of so of
text. Can anyone suggest what is wrong ?
Also, on a side note, why does the size in boundingRectWithSize have to be
315 (i.e slightly shorter than the screen width) rather than 320 in order
to work ? At 320 the textView ends up slightly too wide for the screen.
Thanks !