75 lines
2.3 KiB
JavaScript
75 lines
2.3 KiB
JavaScript
import { motionValue } from './index.mjs';
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import { JSAnimation } from '../animation/JSAnimation.mjs';
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import { isMotionValue } from './utils/is-motion-value.mjs';
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import { frame } from '../frameloop/frame.mjs';
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/**
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* Create a `MotionValue` that animates to its latest value using a spring.
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* Can either be a value or track another `MotionValue`.
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*
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* ```jsx
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* const x = motionValue(0)
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* const y = transformValue(() => x.get() * 2) // double x
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* ```
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*
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* @param transformer - A transform function. This function must be pure with no side-effects or conditional statements.
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* @returns `MotionValue`
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*
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* @public
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*/
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function springValue(source, options) {
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const initialValue = isMotionValue(source) ? source.get() : source;
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const value = motionValue(initialValue);
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attachSpring(value, source, options);
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return value;
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}
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function attachSpring(value, source, options) {
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const initialValue = value.get();
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let activeAnimation = null;
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let latestValue = initialValue;
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let latestSetter;
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const unit = typeof initialValue === "string"
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? initialValue.replace(/[\d.-]/g, "")
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: undefined;
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const stopAnimation = () => {
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if (activeAnimation) {
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activeAnimation.stop();
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activeAnimation = null;
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}
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};
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const startAnimation = () => {
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stopAnimation();
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activeAnimation = new JSAnimation({
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keyframes: [asNumber(value.get()), asNumber(latestValue)],
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velocity: value.getVelocity(),
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type: "spring",
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restDelta: 0.001,
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restSpeed: 0.01,
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...options,
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onUpdate: latestSetter,
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});
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};
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value.attach((v, set) => {
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latestValue = v;
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latestSetter = (latest) => set(parseValue(latest, unit));
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frame.postRender(startAnimation);
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}, stopAnimation);
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if (isMotionValue(source)) {
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const removeSourceOnChange = source.on("change", (v) => value.set(parseValue(v, unit)));
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const removeValueOnDestroy = value.on("destroy", removeSourceOnChange);
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return () => {
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removeSourceOnChange();
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removeValueOnDestroy();
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};
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}
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return stopAnimation;
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}
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function parseValue(v, unit) {
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return unit ? v + unit : v;
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}
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function asNumber(v) {
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return typeof v === "number" ? v : parseFloat(v);
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}
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export { attachSpring, springValue };
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