CSS grid auto-flow dense and varying image sizes
1 min read

grid-auto-flow: dense tells CSS grid to slot in items where there is space. This shuffles around the visual order of the elements, the DOM tree remains in the original order.

A dense layout can look something like this, where the items appear as dynamic sizes and CSS grid clicks them together where there is space.

(Imagine those colored blocks are images)

To get this to work it's not as easy as just putting images of varying sizes inside the grid container. Each item needs to have the number of columns and rows its spans set.

We can estimate a span number based on an image height and width but we will need to use some Javascript.

A React component for the grid items might look something like this, where the amount of column/rows spanned is calculated based on the image metadata (width/height).

function ImageGridItem({ image }) {
  const style = {
    gridColumnEnd: `span ${getSpanEstimate(image.width)}`,
    gridRowEnd: `span ${getSpanEstimate(image.height)}`,
  }

  return <img style={style} src={image.url} alt={image.alt} />
}

function getSpanEstimate(size) {
  if (size > 250) {
    return 2
  }

  return 1
}

The grid container that wraps these items needs to have that grid-auto-flow: dense property!

.gridContainer {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  grid-template-rows: repeat(auto-fit, 260px);
  grid-auto-flow: dense;
  grid-gap: 0.3rem;
}

The zoom functionality in the example can be created by changing the template column/rows sizing dynamically. CSS variables work well for that.

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