可访问性(Accessibility)

Chart.js charts are rendered on user provided canvas elements. Thus, it is up to the user to create the canvas element in a way that is accessible. The canvas element has support in all browsers and will render on screen but the canvas content will not be accessible to screen readers.

With canvas, the accessibility has to be added with ARIA attributes on the canvas element or added using internal fallback content placed within the opening and closing canvas tags.

This [website](https://pauljadam.com/demos/canvas.html "website") has a more detailed explanation of canvas accessibility as well as in depth examples.

## Examples
These are some examples of accessible canvas elements.

By setting the role and aria-label, this canvas now has an accessible name.

```html
<canvas id="goodCanvas1" width="400" height="100" aria-label="Hello ARIA World" role="img"></canvas>
```

This canvas element has a text alternative via fallback content.

```html
<canvas id="okCanvas2" width="400" height="100">
    <p>Hello Fallback World</p>
</canvas>
```

These are some bad examples of inaccessible canvas elements.

This canvas element does not have an accessible name or role.

```html
<canvas id="badCanvas1" width="400" height="100"></canvas>
```

This canvas element has inaccessible fallback content.

```html
<canvas id="badCanvas2" width="400" height="100">Your browser does not support the canvas element.</canvas>
```