export function createRenderStep(runNextFrame) {
    let toRun = [];
    let toRunNextFrame = [];
    let numToRun = 0;
    let isProcessing = false;
    let flushNextFrame = false;
    const toKeepAlive = new WeakSet();
    const step = {
        schedule: (callback, keepAlive = false, immediate = false) => {
            const addToCurrentFrame = immediate && isProcessing;
            const buffer = addToCurrentFrame ? toRun : toRunNextFrame;
            if (keepAlive)
                toKeepAlive.add(callback);
            if (buffer.indexOf(callback) === -1) {
                buffer.push(callback);
                if (addToCurrentFrame && isProcessing)
                    numToRun = toRun.length;
            }
            return callback;
        },
        cancel: (callback) => {
            const index = toRunNextFrame.indexOf(callback);
            if (index !== -1)
                toRunNextFrame.splice(index, 1);
            toKeepAlive.delete(callback);
        },
        process: (frameData) => {
            if (isProcessing) {
                flushNextFrame = true;
                return;
            }
            isProcessing = true;
            [toRun, toRunNextFrame] = [toRunNextFrame, toRun];
            toRunNextFrame.length = 0;
            numToRun = toRun.length;
            if (numToRun) {
                for (let i = 0; i < numToRun; i++) {
                    const callback = toRun[i];
                    callback(frameData);
                    if (toKeepAlive.has(callback)) {
                        step.schedule(callback);
                        runNextFrame();
                    }
                }
            }
            isProcessing = false;
            if (flushNextFrame) {
                flushNextFrame = false;
                step.process(frameData);
            }
        },
    };
    return step;
}
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