[cssom] What should happen with getComputedStyle on a node in another document when used values are involved?

From: Boris Zbarsky <bzbarsky@mit.edu> Date: Tue, 09 Dec 2014 10:47:51 -0500 Message-ID: <548719A7.2030805@mit.edu> To: www-style@w3.org · This archive was generated by hypermail 2.4.0 : Friday, 25 March 2022 10:08:49 UTC

Consider this testcase:

<!DOCTYPE html>
<iframe srcdoc="<div style='width: 100%'>"
         style="width: 200px">
</iframe>
<script>
onload = function() {
   alert(
     getComputedStyle(frames[0].document.querySelector("div")).width
   );
}
</script>

What should be alerted?

Per spec, this should be "the value [of width] being the resolved value 
computed for obj using the style rules associated with doc", where "doc" 
is the parent document.

But for "width" the resolved value is the used value.  How exactly is 
this supposed to be calculated "using the style rules associated with doc"?

-Boris