main repo

node_modules/motion-dom/dist/es/value/spring-value.mjs

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