title: Why is lineHeight of UIFont larger than font size?
body: <p>I use the code below to calculate the number of lines of string with limited width.</p>
  
  <pre><code>NSString *text = @"abcdefgh";
  UIFont *font = [UIFont systemFontOfSize:15.0];
  CGFloat h = [text suggestHeightWithFont:font width:320.0];
  NSInteger lines = (h &gt; font.lineHeight) ? h/font.lineHeight+1 : h/font.lineHeight;
  NSLog(@"height %f, %f, number lines:%ld", h, font.lineHeight, (unsigned long)lines);
  </code></pre>
  
  <p>But I found that <code>font.lineHeight</code> (log shows it is 17.900391) is larger than the font size which is set as <code>15.0</code>.</p>
  
  <p>The log message shows:</p>
  
  <blockquote>
    <p>height 17.900391, 17.900391, number lines:1</p>
  </blockquote>