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The PaintWorklet.registerPaint()
method of the PaintWorklet
interface registers a class programmatically generate an image where a CSS property expects a file.
Syntax
registerPaint(name, class);
Parameters
- name
- The name of the worklet class to register.
- class
- A reference to the class that implements the worklet.
Return value
Exceptions
- TypeError
- Thrown when one of the arguments is invalid or missing.
- InvalidModificationError
- Thrown when the a worklet already exists with the specified name.
Examples
The following shows registering an example worklet module. This should be in a separate js file. Note that registerPaint()
is called without a reference to PaintWorklet
. The file itself is loaded through CSS.paintWorklet.addModule()
(documented here on the parent class of PaintWorklet, at Worklet.addModule()
.
/* checkboardWorklet.js */
class CheckerboardPainter {
paint(ctx, geom, properties) {
// Use `ctx` as if it was a normal canvas
const colors = ['red', 'green', 'blue'];
const size = 32;
for(let y = 0; y < geom.height/size; y++) {
for(let x = 0; x < geom.width/size; x++) {
const color = colors[(x + y) % colors.length];
ctx.beginPath();
ctx.fillStyle = color;
ctx.rect(x * size, y * size, size, size);
ctx.fill();
}
}
}
}
// Register our class under a specific name
registerPaint('checkerboard', CheckerboardPainter);
The first step in using a paintworket is defining the paint worklet using the registerPaint()
function, as done above. To use it, you register it with the CSS.paintWorklet.addModule()
method:
<script>
CSS.paintWorklet.addModule('checkboardWorklet.js');
</script>
You can then use the paint()
CSS function in your CSS anywhere an <image>
value is valid.
li {
background-image: paint(checkerboard);
}
Specifications
Specification | Status | Comment |
CSS Painting API Level 1The definition of 'PaintWorklet.registerPaint' in that specification. | Working Draft | Initial definition. |
Browser compatibility
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See Also
PaintWorklet.registerPaint by Mozilla Contributors is licensed under CC-BY-SA 2.5.