Grid, content re-ordering and accessibility

Take this:

<ol>
  <li>Get hungry</li>
  <li>Order pizza</li>
  <li>Eat pizza</li>
</ol>

That HTML ends up in the DOM that way (and thus how it is is exposed to assistive technology), and by default, those list items are also visually shown in that order. In most layout situations, the visual order will match that DOM order. Do nothing, and the list items will flow in the block direction of the document. Apply flexbox, and it will flow in the inline direction of the document.

But flexbox and grid also allow you to muck it up. Now take this:

ol { 
  display: flex;
  flex-direction: row-reverse;
}

In this case, the DOM order still makes sense, but the visual order is all wrong. It’s not just row-reverse. There are a number of flexbox and grid properties that can get involved and confuse things: the order property, flowing items into columns instead of rows, and positioning items specifically in unusual orders, among others. Even absolute positioning could cause the same trouble.

Manuel Matuzovic says:

If the visual order and the DOM order don’t match, it can irritate and confuse users up to a point where the experience is so bad that the site is unusable.

Rachel Andrew highlights this issue (including things we’ve published) as a big issue, and hopes we can get tools at the CSS level to help.

I think this is something we sorely need to address at a CSS level. We need to provide a way to allow the tab and reading order to follow the visual order. Source order is a good default, if you are taking advantage of normal flow, a lot of the time following the source is exactly what you want. However not always, not at every breakpoint. If we don’t give people a solution for this, we will end up with a mess. We’ve given people these great tools, and now I feel as if I’m having to tell people not to use them.

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