paint(workletName, ...parameters)

where:

workletName

The name of the registered worklet.

parameters

Optional additional parameters to pass to the paintWorklet

In JavaScript, we register the paint worklet:

CSS.paintWorklet.addModule("boxbg.js");

...then, in the CSS, we define the background-image as a paint() type with the worklet name, boxbg, along with any variables (ex. --boxColor and --widthSubtractor) the worklet will use:

li {
  background-image: paint(boxbg);
  --boxColor: hsl(55 90% 60% / 1);
}
li:nth-of-type(3n) {
  --boxColor: hsl(155 90% 60% / 1);
  --widthSubtractor: 20;
}
li:nth-of-type(3n + 1) {
  --boxColor: hsl(255 90% 60% / 1);
  --widthSubtractor: 40;
}

The result will be the following:

You can pass additional arguments via the CSS paint() function. In this example, we passed two arguments: whether the background-image on a group of list items is filled or just has a stroke outline, and the width of that outline:

li {
  --boxColor: hsl(55 90% 60% / 1);
  background-image: paint(hollowHighlights, stroke, 2px);
}

li:nth-of-type(3n) {
  --boxColor: hsl(155 90% 60% / 1);
  background-image: paint(hollowHighlights, filled, 3px);
}

li:nth-of-type(3n + 1) {
  --boxColor: hsl(255 90% 60% / 1);
  background-image: paint(hollowHighlights, stroke, 1px);
}

We've included a custom property in the selector block defining a boxColor. Custom properties are accessible to the PaintWorklet.

• PaintWorklet
• CSS Painting API
• Using the CSS Painting API
• <image>
• Canvas API