material-motion/dist/getFrame$.js

Makes it easy to add rich, interactive motion to your application.

/** @license
 *  Copyright 2016 - present The Material Motion Authors. All Rights Reserved.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may not
 *  use this file except in compliance with the License. You may obtain a copy
 *  of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 *  License for the specific language governing permissions and limitations
 *  under the License.
 */
import { MotionObservable, } from './observables/proxies';
/**
 * A stream backed by `requestAnimationFrame`, called once per frame with that
 * frame's timestamp.
 *
 * Useful as a pulse for `_debounce` to ensure that UI work only happens once
 * per frame.  Since no rendering will happen until `requestAnimationFrame` is
 * called, it should be safe to `_debounce({ pulse$: frame$ })` without missing
 * a frame.
 */
let frame$;
export function getFrame$() {
    if (!frame$) {
        frame$ = new MotionObservable((observer) => {
            let queuedFrameID = 0;
            function queueFrame(frameTimestamp) {
                if (frameTimestamp) {
                    observer.next(frameTimestamp);
                }
                queuedFrameID = requestAnimationFrame(queueFrame);
            }
            queueFrame();
            return () => {
                cancelAnimationFrame(queuedFrameID);
            };
        })._multicast();
    }
    return frame$;
}
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