zulip/static/js/scroll_bar.js

$(function () {
    $("#stream-filters-container").perfectScrollbar({
        suppressScrollX: true,
        useKeyboard: false,
        wheelSpeed: 0.5,
    });
});


// From https://stackoverflow.com/questions/13382516/getting-scroll-bar-width-using-javascript
function getScrollbarWidth() {
    var outer = document.createElement("div");
    outer.style.visibility = "hidden";
    outer.style.width = "100px";
    outer.style.msOverflowStyle = "scrollbar"; // needed for WinJS apps

    document.body.appendChild(outer);

    var widthNoScroll = outer.offsetWidth;
    // force scrollbars
    outer.style.overflow = "scroll";

    // add innerdiv
    var inner = document.createElement("div");
    inner.style.width = "100%";
    outer.appendChild(inner);

    var widthWithScroll = inner.offsetWidth;

    // remove divs
    outer.parentNode.removeChild(outer);

    return widthNoScroll - widthWithScroll;
}


// Workaround for browsers with fixed scrollbars
$(function () {
   var sbWidth = getScrollbarWidth();

   if (sbWidth > 0) {
    $(".header").css("left", "-" + sbWidth + "px");
    $(".header-main").css("left", sbWidth + "px");
    $(".header-main").css("max-width", (1400 + sbWidth) + "px");
    $(".header-main .column-middle").css("margin-right", (250 + sbWidth) + "px");

    $(".fixed-app").css("left", "-" + sbWidth + "px");
    $(".fixed-app .app-main").css("max-width", (1400 + sbWidth) + "px");
    $(".fixed-app .column-middle").css("margin-left", (250 + sbWidth) + "px");

    $(".column-right").css("right", sbWidth + "px");
    $(".app-main .right-sidebar").css({"margin-left": (sbWidth) + "px",
                                       width: (250 - sbWidth) + "px"});

    $("#compose").css("left", "-" + sbWidth + "px");
    $(".compose-content").css({left: sbWidth + "px",
                               "margin-right": (250 + sbWidth) + "px"});
    $("#compose-container").css("max-width", (1400 + sbWidth) + "px");

    $("head").append("<style> @media (max-width: 975px) { .compose-content, .header-main .column-middle { margin-right: " + (7 + sbWidth) + "px !important; } } " +
                     "@media (max-width: 775px) { .fixed-app .column-middle { margin-left: " + (7 + sbWidth) + "px !important; } } " +
                     "</style>");
   }

});