title: 2-line label ggplot looks abnormal
body: <p>I have a problem with complex 2-line axis label which contains formatting in first part of it. </p>
  
  <pre><code>library(ggplot2)
  df &lt;- data.frame(Groups=c("A", "B"), Values = c(1,2))
  label2 &lt;- expression(paste(italic("The quick brown fox jumps over the\n lazy dog."), " Non-italic part of label"))
  ggplot(df, aes(x = Groups, y = Values)) +  
    geom_bar(stat="identity") + 
    scale_x_discrete("Labels", labels=c("Short label", label2))+
    theme(axis.text.x = element_text(angle = 45, hjust = 1))
  </code></pre>
  
  <p>Result image doesn't look good (there are long empty space in the second line of the long label. So the label is oversized and the second line looks interrupted) and I can't find any way to resolve this problem. </p>
  
  <p>I have also tried a more complicated expression, but separator did not positioned in the correct way.</p>
  
  <pre><code>label3 &lt;- expression(paste(italic("The quick brown fox jumps over the"), paste(italic("lazy dog."), "Non-italic part of label"), sep = "\nSEP"))
  </code></pre>
  
  <p>Please share some ideas how to align second line correctly?</p>
  
  <p><img src="https://i.stack.imgur.com/v3EL2.png" alt="enter image description here"></p>