@pdftron/webviewer-react-toolkit/dist/esm/hooks/useFileSubscribe.js

A React component library for integrating with PDFTron WebViewer API.

import { useEffect, useMemo, useRef, useState } from 'react';
import { MemoizedPromise } from '../data';
import GlobalQueue from '../work/GlobalQueue';
/**
 * Will subscribe to a value from a file and return the value, as well as any
 * async errors.
 * @param file The file to subscribe to.
 * @param getCurrentValue Function to extract the current value from the file.
 * @param eventType The event type to subscribe. Won't subscribe if not given.
 * @param throttle The timeout to throttle initial fetch of value. Default: 500ms.
 */
export function useFileSubscribe(file, getCurrentValue, eventType) {
    var getValue = useRef(getCurrentValue);
    var _a = useState(), error = _a[0], setError = _a[1];
    var _b = useState(function () {
        var currentValue = getValue.current(file);
        if (currentValue instanceof MemoizedPromise)
            return undefined;
        return currentValue;
    }), value = _b[0], setValue = _b[1];
    useEffect(function () {
        var cancelled = false;
        var cancel;
        var setMemoValue = function (val) {
            try {
                if (!cancelled)
                    setValue(val);
            }
            catch (error) {
                if (!cancelled)
                    setError(error);
            }
        };
        var subscribe = function () {
            setError(undefined);
            var val = getValue.current(file);
            if (!(val instanceof MemoizedPromise)) {
                // Non-memoized-promise, can set directly.
                setValue(val);
                return;
            }
            setValue(undefined);
            if (val.done) {
                val.get().then(setMemoValue);
            }
            else {
                var r = GlobalQueue.process(function () { return val.get(); });
                cancel = r[1];
                r[0]
                    .then(function (result) {
                    setMemoValue(result);
                })
                    .catch(function (e) {
                    setError(e);
                });
            }
        };
        subscribe();
        var unsubscribe;
        if (eventType)
            unsubscribe = file.subscribe(eventType, subscribe);
        return function () {
            cancel === null || cancel === void 0 ? void 0 : cancel();
            unsubscribe === null || unsubscribe === void 0 ? void 0 : unsubscribe();
            cancelled = true;
        };
    }, [eventType, file]);
    return useMemo(function () { return [value, error, setValue]; }, [error, value]);
}