title: How to make a frame with border in gnuplot?
body: <p>I am trying to make a frame for a density plot. I start with</p>
  
  <pre><code>set terminal pngcairo size 400,400 enhanced
  set output 'test.png'
  
  set view map
  unset tics
  unset colorbox
  set size ratio 1
  
  set border 15 front lw 20
  #set border 15 back lw 20
  
  splot sin(sqrt(x**2+y**2))/sqrt(x**2+y**2) w pm3d notitle
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Fvymu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Fvymu.png" alt="enter image description here"></a></p>
  
  <p>If I use <code>front</code> the border looks continuous, but it eats a portion of the plot. If I use <code>back</code>, it no longer looks like a frame. </p>
  
  <p>How can I make a proper frame such that it stays out of the plot region? </p>