title: Can specific text character change the line height?
body: <p>I have this code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;p style="line-height: 1;overflow: hidden;"&gt;blah_blah&lt;/p&gt;
  &lt;p&gt;blah_blah&lt;/p&gt;
  
  &lt;p style="line-height: 1;overflow: hidden;"&gt;qypj;,&lt;/p&gt;
  &lt;p&gt;qypj;,&lt;/p&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>which results in (notice no underscore, and cut characters):
  <hr/>
  <a href="https://i.stack.imgur.com/QQLuS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QQLuS.png" alt="enter image description here"></a></p>
  
  <hr/>
  
  <p>That is, it behaves that way in Firefox (66.0.3 on Windows 10). Other browsers seem to render the underscore. The above snippet runner also seems to work (even in Firefox), unless you run it in "Full page".</p>
  
  <p>This Q is similar to <a href="https://stackoverflow.com/questions/38898803/text-changes-height-after-adding-unicode-character">Text changes height after adding unicode character</a> except there are no tricks here. "_" is just a simple ASCII character.</p>
  
  <p>My question is which behavior is the correct one.
  Is specific character allowed to change line height (I thought it was only supposed to be font dependent)? Shouldn't <code>line-height: 1</code> imply it can fit exactly any text?</p>
  
  <p>I suppose some characters are special, such as "p", "g", "j" (and possibly "_") that draw below its line. Still which behavior is the correct one. Is it considered overflow or not?</p>
  
  <p>PS: Furthermore I find it funny <strong>either</strong> <code>overflow-x: hidden;overflow-y: visible;</code> and <code>overflow-x: visible;overflow-y: hidden;</code> still causes this. Which seems more like an actual bug to me.</p>