title: GetBoundingClientRect doesn't work outside the window
body: <p>I am making a script that should measure distances in a post. For example, if i have three posts:</p>
  
  <ul>
  <li>Post 1: <em>two lines of text, then the image that I want to see.</em></li>
  <li>Post 2: <em>Just the image that I want to see.</em></li>
  <li>Post 3: <em>The image I want to see Followed by two lines.</em></li>
  </ul>
  
  <p><strong>The reason I want this, is because I think Tumblr displays too much nonsense in their discriptions. I am making a chrome extension that will crop all the nonsense around images so that you have to scroll less. on every posts will apear a button to see the whole post.</strong></p>
  
  <p>As of today, it works great! With <code>getBoundingClientRect</code> I can get the top, left, bottom and right offset from the window. There is just 1 problem. I can not do it for all the posts on a page right away, because if a post is 700px or more away of the visible part of the document, the part you're viewing in the browser, all the values provided by GBCR will be 0.</p>
  
  <p>These values are not valid, and are probably zero because the post isn't rendered on screen. And I could make my extension try to get the dimensions if I scroll, so that when a post gets in the visible part of the window, it is processed. But this doesnt have my preference. This would mean my JS functions have to be <em>triggered</em> every time a user scrolls, which is bad practice. I much rather start my functions when the dom is loaded, so if new posts are added, the functions will be triggered.</p>
  
  <hr />
  
  <p>My question for you is the following: Is there a workaround to make sure the function GBCR works when the post is not rendered on screen. Or is there a way that I can get the Coordinats of an element with <code>getComputedStyle</code> (without going through all the elements)?</p>