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Centring Overlapping Content with CSS Grid

bennypowers profile image Benny Powers ๐Ÿ‡ฎ๐Ÿ‡ฑ๐Ÿ‡จ๐Ÿ‡ฆ ใƒป1 min read

So you've got an image and you want to centre some content over it.

<figure id="beshalach">
  <a href="/beshalach-1520/"><img src="./images/beshalach-15-20.jpg" alt="Exodus 15:20" /></a>
  <figcaption><a href="/beshalach-1520/">Exodus 15:20</a></figcaption>
</figure>

In the past, you'd probably have reached for our old friend absolute positioning:

figure {
  position: relative;
}

figcaption {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

This is fine. git commit -m "Job's done" && git push. Buuut maybe we can do a little better. Using CSS grid we can accomplish the same result, but in what strikes me as a more declarative syntax.

figure {
  display: grid;
  place-items: center;
  grid-template-areas: 'image'
}

figure > * {
  grid-area: image;
}

With these rules, we've defined a 1-by-1 grid with a single area named 'images', which all of its content fits into. With that established, the source order takes over to paint the caption on top of the image. No need for position, z-index, etc.

This has several advantages:

  1. It's declarative. These styles describe the intended outcome, instead of the steps the developer thought should be taken.
  2. It's readable. I don't know about you, but future me probably wouldn't see top: 50%; left: 50%; transform: translate(-50%, -50%); and immediately think "centred!"
  3. Flex and Grid have a simpler mental model for stacking context which is the darkest of black arts.

So next time you need to overlap content, consider using grid instead of position.

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