Centering legend in Firefox

Question

The problem

The problem is that the following works in Chrome, Opera and IE ^_(!?) but does not work in Firefox:

fieldset>legend {
  display: table;
  float: none;
  margin: 0 auto;
}

<fieldset>
  <legend>Legend</legend>
</fieldset>

Result in Chrome

Result in Firefox

Solutions Hacks

There are a few questions around but none have satisfying answers:

/* intended styling */
fieldset>legend {
    display: table;
    float: none;
    margin: 0 auto;
}

fieldset.absolute-fix {
    position: relative;
}
fieldset.absolute-fix>legend {
    position: absolute;
    left: 50%;
}

fieldset.margin-fix>legend {
    margin-left: 50%;
    margin-right: 50%;
    width: auto;
    transform: translate(-50%, 0)
}

fieldset.width-fix>legend {
    width: 100%;
    text-align: center;
}

<fieldset class="absolute-fix">
    <legend>Fix with absolute</legend>
    <p>Not centered and inconsitant styling</p>
    <a href="http://stackoverflow.com/a/4006871/1185053">Source</a>
</fieldset>

<fieldset class="attribute-fix">
    <legend align="center">Fix with attribute</legend>
    <p>Requires use of depreciated HTML and strongly ties presentation to content.</p>
    <a href="http://stackoverflow.com/a/19969606/1185053">Source</a>
</fieldset>

<fieldset class="margin-fix">
    <legend>Fix with margin</legend>
    <p>This is unsatisfying because there is a mis-aligned gap in the border and long legends go over several lines.</p>
</fieldset>

<fieldset class="width-fix">
    <legend>Fix with width</legend>
    <p>This is unsatisfying because there is a gaping hole in the border.</p>
</fieldset>

Question

Is there a way to constantly center legend in Firefox, whilst maintaining styling for other browsers?

Answer 1

This solution uses a Firefox specific selector so we don't need to touch the styling for the other browsers. It uses absolute positioning but uses the transform property to center appropriately.

/* indended styling for other browsers */
fieldset>legend {
  display: table;
  float: none;
  margin: 0 auto;
}

/* FF only */
@media screen and (-moz-images-in-menus: 0) {
  fieldset {
    position: relative;
  }
  fieldset>legend {
    position: absolute;
    left: 50%;
    top: -12px; /* depends on font size and border */
    background: white; /* depends on background */
    transform: translate(-50%, 0);
  }
}

<fieldset>
  <legend>Fix using absolute and transform</legend>
  <p>This seems to work a bit better.</p>
</fieldset>

Result in Chrome

Result in Firefox