Future CSS: :drag (and Maybe ::dragged-image?)

Now, I know what you’re thinking. Yet another CSS pseudo-class… But I think this suggestion is rather cool.

Earlier this year, it was proposed to add a new pseudo-class, :drag, that would enable developers to apply styles when an element is being actively dragged by the user. Currently, CSS lacks a mechanism to detect drag interactions, making it difficult to manage UI behaviors that depend on this action without relying on JavaScript.

No JavaScript! I like the idea of having a pseudo-class dedicated to this function rather than going through the classList.toggle() route.

But, how would this work, though?

To understand, you first have to know that the HTML Drag and Drop API. Some of the events it fires include: 

• drag (fires every few milliseconds when the element is dragged), 
• dragstart (event fires at the initial drag), and 
• dragend (event fires when the dragging the element stops).

Let’s take a quick look at how these drag-and-drop events work in JavaScript in order to understand how they would translate in CSS. Imagine we have seven button elements in a <div> :

<menu class="menu-bar">
  <li><button>Home</button></li>
  <li><button>Products</button></li>
  <li><button>Services</button></li>
  <li><button>About</button></li>
  <li><button>Contact</button></li>
  <li><button>Blog</button></li>
  <li><button>Careers</button></li>
</div>

We can make the entire .menu-bar draggable by slapping an attribute on it:

<menu class="menu-bar" draggable="true">
  <!-- etc. -->
</div>

For our CSS, we simply give the is-dragging class some styling, which will be applied only when the element is dragged or moved:

In CSS, we can set up an .is-dragging class that we’ll set on the element with JavaScript when it’s in the process of being dragged. These are the styles we apply to the element when that’s happening:

.is-dragging {
  box-shadow: 0 4px 12px rgba(0 0 0 / 0.15);
  background: #fff;
  transform: translate(1px);
  opacity: 0.2;
  scale: 1.2;
}

And here’s the JavaScript to toggle between the start of the mouse drag and its end. It listens for a dragstar event and adds the .is-dragging class to the .menu-bar. And when we drop the .menu-bar, the dragging fun stops and the .is-dragging class is removed:

menuBar.addEventListener("dragstart", (event) => {
  event.target.classList.add("is-dragging");
});

menuBar.addEventListener("dragend", (event) => {
  event.target.classList.remove("is-dragging");
});

Our output would look something like this. Drag the dropdown element to see:

Not bad! When the menu bar is dragged, it retains an image of itself in its original position that is styled with the .is-dragging class. And while we were totally able to knock this out with JavaScript, how cool would it be to have that proposed :drag pseudo-class to abstract all that script-y stuff:

.menu-bar:drag {
  cursor: grabbing;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  background: #fff;
  transform: translate(1px);
  opacity: 0.2;
  scale: 1.2;
}

+1 for performance! +1 for one less dependency! +1 for maintainability!

How about the preview image?

Did you know we can style the actual element itself as it’s being dragged around the screen? That’s called the preview image and we can replace it with a <div> that we can add custom styling to.

It’s just a little more JavaScript using the dataTransfer.setDragImage() function:

const dragPreview = document.createElement("div");

dragPreview.textContent = "📦 Dragging...";
dragPreview.style.cssText = `
  background: #fff6d6;
  border: 2px dashed orange;
  border-radius: 0.5rem;
  color: #333;
  padding: 0.5rem 1rem;
`;

document.body.appendChild(dragPreview);

// This replaces the default drag preview
event.dataTransfer.setDragImage(dragPreview, 0, 0);

// Remove after the event fires
setTimeout(() => dragPreview.remove(), 0);

Here’s where I’ll go out on a limb and suggest another CSS pseudo specifically for that ::drag-image. Imagine being able to sidestep all that JavaScript and straight-up write the styles in CSS:

::drag-image {
  content: "📦 Dragging...";
  padding: 0.5rem 1rem;
  background: #fff6d6;
  color: #333;
  border: 2px dashed orange;
  border-radius: 0.5rem;
}

I suppose it could be a pseudo-class instead, but it feels like a pseudo-element makes more sense since we’re talking about a specific object rather than a state.

I opened an issue for that — give it a thumbs-up if you’d find it handy to have a ::drag-image pseudo-element like that. The CSSWG is already slated to discuss the :drag proposal. If that gets baked into the specifications, then I’d push for the pseudo-element, too.

Thoughts?

Yea or nay for drag-related pseudos? Would you reach for something like that, or do you feel steps on JavaScript’s toes too much?

Future CSS: :drag (and Maybe ::dragged-image?) originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.