Element: contentvisibilityautostatechanged event

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The contentvisibilityautostatechanged event fires on any element with content-visibility: auto set on it when it starts or stops being relevant to the user and skipping its contents.

This means that the user agent skips an element's rendering (including layout and painting) until it is needed, making page rendering much faster.

The contentvisibilityautostatechanged event provides a way for an app's code to start or stop rendering processes (e.g. drawing on a <canvas>) when they are not needed, thereby conserving processing power. It should be noted that, even when hidden from view, element contents will remain semantically relevant (e.g. to assistive technology users), so this signal should not be used to skip significant semantic DOM updates.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("contentvisibilityautostatechanged", (event) => {});
contentvisibilityautostatechanged = (event) => {};

Note: The event object is of type ContentVisibilityAutoStateChangedEvent.

Examples

const canvasElem = document.querySelector('canvas');

canvasElem.addEventListener('contentvisibilityautostatechanged', stateChanged);
canvasElem.style.contentVisibility = "auto";

function stateChanged(event) {
  if (event.skipped) {
    stopCanvasUpdates(canvasElem);
  } else {
    startCanvasUpdates(canvasElem);
  }
}

// Call this when the canvas updates need to start.
function startCanvasUpdates(canvas) {
  // … 
}

// Call this when the canvas updates need to stop.
function stopCanvasUpdates(canvas) {
  // …
}

Specifications

Specification
CSS Containment Module Level 2
# content-visibility-auto-state-changed

Browser compatibility

BCD tables only load in the browser

See also