radare/radare2-webui

/**
 * domTarget must have a "measurable" height
 * limit, when there is less than {limit}% available to scroll
 * we call the associated event
 */
export class InfiniteScrolling {

    constructor(domTarget, howManyScreens, limit) {
        this.domTarget = domTarget;
        this.limit = limit;
        this.howManyScreens = howManyScreens;
        this.screenProportion = 1.0 / this.howManyScreens;
        this.pauseScrollEvent = false;
        this.prevScroll = 0.;

        var _this = this;
        this.domTarget.addEventListener('scroll', function(e) {
            _this.scrollEvent_(e);
        });
    }

    setTopEvent(fct) {
        this.ontop = fct;
    }

    setBottomEvent(fct) {
        this.onbottom = fct;
    }

    scrollEvent_(e) {
        var _this = this;
        if (this.pauseScrollEvent) {
            return;
        }

        var height = e.target.scrollHeight - e.target.offsetHeight;
        var p = e.target.scrollTop  / height;

        if (!this.isTopMax && p < this.limit && this.prevScroll > p) {
            this.pauseScrollEvent = true;
            var pos = Math.floor(((this.limit + (p - this.limit)) + this.screenProportion) * height);
            this.ontop(pos, function(isTopMax) {
                _this.pauseScrollEvent = false;
            });
        }

        if (p > (1 - this.limit) && this.prevScroll < p) {
            this.pauseScrollEvent = true;
            var pos = Math.floor((((1 - this.limit) + (p - (1 - this.limit))) - this.screenProportion) * height);
            this.onbottom(pos, function(isTopMax) {
                _this.pauseScrollEvent = false;
            });
        }

        this.prevScroll = p;
    }
}