gecko-dev/layout/reftests/columns/fieldset-columns-002.html

<!DOCTYPE HTML>
<html>
  <style>
  div {
    position: absolute;
    width: 10px;
    height: 10px;
    top: 0;
    background: blue;
  }
  fieldset {
    width: 300px;
    height: 200px;
    border: 1px solid;
    position: relative;
    overflow: hidden;
  }
  </style>
  <fieldset style="columns: 1;">
    <!-- The position of <div>s should remain the same regardless of
         the multicol style on fieldset. -->
    <legend>Legend<div style="left: 0px;"></div></legend>
    <div style="left: 10px;"></div>
  </fieldset>
</html>
Bug 1535200 Part 1 - In fieldset, make absolute positioned frames relative to multicol container, not the column content frames. r=mats Per spec, "Note: Column boxes do not become the containing block for elements with position: fixed or position: absolute. The containing block is the multicol container, it being the principal box." https://drafts.csswg.org/css-multicol-1/#the-multi-column-model contentFrame and contentFrameTop are different only if fieldset has multicol layout. In that case, contentFrameTop is nsColumnSetFrame (or ColumnSetWrapperFrame after applying Part 2 with layout.css.column-span.enabled=true). Differential Revision: https://phabricator.services.mozilla.com/D23617 --HG-- extra : moz-landing-system : lando 2019-03-18 08:47:53 +03:00			`<!DOCTYPE HTML>`
			`<html>`
			`<style>`
			`div {`
			`position: absolute;`
			`width: 10px;`
			`height: 10px;`
			`top: 0;`
			`background: blue;`
			`}`
			`fieldset {`
			`width: 300px;`
			`height: 200px;`
			`border: 1px solid;`
			`position: relative;`
			`overflow: hidden;`
			`}`
			`</style>`
			`<fieldset style="columns: 1;">`
			`<!-- The position of <div>s should remain the same regardless of`
			`the multicol style on fieldset. -->`
			`<legend>Legend<div style="left: 0px;"></div></legend>`
			`<div style="left: 10px;"></div>`
			`</fieldset>`
			`</html>`