Unwanted Vertical Padding from iOS 6 on CATextLayer

Question

Background: I started my project in iOS 5 and built out a beautiful button with layer. I added a textLayer onto the button and center it using the following cod

Answer 1

t0rst's answer helps me. I think capHeight and xHeight are key.

    CATextLayer *mytextLayer = [CATextLayer layer];
    CGFloat fontSize = 30;
    UIFont *boldFont = [UIFont boldSystemFontOfSize:fontSize];
    mytextLayer.font = (__bridge CFTypeRef)(boldFont.fontName);
    mytextLayer.fontSize = fontSize;

    CGFloat offsetY = 0;

    //if system version is grater than 6
    if(([[[UIDevice currentDevice] systemVersion] compare:@"6" options:NSNumericSearch] == NSOrderedDescending)){
        offsetY = -(boldFont.capHeight - boldFont.xHeight);
    }

    //you have to set textX, textY, textWidth
    mytextLayer.frame = CGRectMake(textX, textY + offsetY, textWidth, fontSize);