mirror of https://github.com/sveltejs/svelte
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
73 lines
2.0 KiB
73 lines
2.0 KiB
---
|
|
title: Custom CSS transitions
|
|
---
|
|
|
|
The `svelte/transition` module has a handful of built-in transitions, but it's very easy to create your own. By way of example, this is the source of the `fade` transition:
|
|
|
|
```js
|
|
function fade(node, {
|
|
delay = 0,
|
|
duration = 400
|
|
}) {
|
|
const o = +getComputedStyle(node).opacity;
|
|
|
|
return {
|
|
delay,
|
|
duration,
|
|
css: t => `opacity: ${t * o}`
|
|
};
|
|
}
|
|
```
|
|
|
|
The function takes two arguments — the node to which the transition is applied, and any parameters that were passed in — and returns a transition object which can have the following properties:
|
|
|
|
* `delay` — milliseconds before the transition begins
|
|
* `duration` — length of the transition in milliseconds
|
|
* `easing` — a `p => t` easing function (see the chapter on [tweening](tutorial/tweened))
|
|
* `css` — a `(t, u) => css` function, where `u === 1 - t`
|
|
* `tick` — a `(t, u) => {...}` function that has some effect on the node
|
|
|
|
The `t` value is `0` at the beginning of an intro or the end of an outro, and `1` at the end of an intro or beginning of an outro.
|
|
|
|
Most of the time you should return the `css` property and *not* the `tick` property, as CSS animations run off the main thread to prevent jank where possible. Svelte 'simulates' the transition and constructs a CSS animation, then lets it run.
|
|
|
|
For example, the `fade` transition generates a CSS animation somewhat like this:
|
|
|
|
```css
|
|
0% { opacity: 0 }
|
|
10% { opacity: 0.1 }
|
|
20% { opacity: 0.2 }
|
|
/* ... */
|
|
100% { opacity: 1 }
|
|
```
|
|
|
|
We can get a lot more creative though. Let's make something truly gratuitous:
|
|
|
|
```html
|
|
<script>
|
|
import { fade } from 'svelte/transition';
|
|
import { elasticOut } from 'svelte/easing';
|
|
|
|
let visible = true;
|
|
|
|
function spin(node, { duration }) {
|
|
return {
|
|
duration,
|
|
css: t => {
|
|
const eased = elasticOut(t);
|
|
|
|
return `
|
|
transform: scale(${eased}) rotate(${eased * 1080}deg);
|
|
color: hsl(
|
|
${~~(t * 360)},
|
|
${Math.min(100, 1000 - 1000 * t)}%,
|
|
${Math.min(50, 500 - 500 * t)}%
|
|
);`
|
|
}
|
|
};
|
|
}
|
|
</script>
|
|
```
|
|
|
|
Remember: with great power comes great responsibility.
|