r is within the plot panel&gt;'</span><span class="op">)</span> <span class="op">{</span>
      <span class="kw">if</span> <span class="op">(</span><span class="st">'&lt;mouse cursor is within a stratum box&gt;'</span><span class="op">)</span> <span class="op">{</span>
        <span class="st">'&lt;Render stratum tooltip.&gt;'</span>
      <span class="op">}</span> <span class="kw">else</span> <span class="op">{</span>
        <span class="kw">if</span> <span class="op">(</span><span class="st">'&lt;mouse c