ldr_smooth_scroll.user.js

// ==UserScript==
// @name           ldr smooth scroll
// @namespace      http://relaxedcolumn.blog8.fc2.com/
// @description    smoothing scroll for livedoor reader (ldr) and fastladder
// @include        http://reader.livedoor.com/reader/
// @include        http://reader.livedoor.com/public/*
// @include        http://fastladder.com/reader/
// ==/UserScript==
//

(function() {

// shorthand
var _gm = !!this.unsafeWindow;
var _w = this.unsafeWindow || window;
var $ = _w.$;
var container = $("right_container");

// config
var config = {
    type:      "always",
    threshold: 300,
    duration:  300,
    easing:    "easeInOutCubic"
};

// load config
if(_gm) for(var val in config) config[val] = GM_getValue(val, config[val]);

// easing
var easingFunctions = {
    linear: function(t, b, c, d) {
        return c * t / d + b;
    },

    easeInOutCubic: function(t, b, c, d) {
        if((t/=d/2) < 1) return c /2*t*t*t + b;
        else return c/2*((t-=2)*t*t + 2) + b;
    },

    easeInOutSine: function(t, b, c, d) {
        return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
    },

    easeInBounce: function(t, b, c, d) {
        return c - easingFunctions.easeOutBounce(d-t, 0, c, d) + b;
    },

    easeOutBounce: function(t, b, c, d) {
        if((t/=d) <(1/2.75)) {
            return c*(7.5625*t*t) + b;
        } else if(t <(2/2.75)) {
            return c*(7.5625*(t-=(1.5/2.75))*t + .75) + b;
        } else if(t <(2.5/2.75)) {
            return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
        } else {
            return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;
        }
    },

    easeInOutBounce: function(t, b, c, d) {
        if(t < d/2) return easingFunctions.easeInBounce(t*2, 0, c, d) * .5 + b;
        else return easingFunctions.easeOutBounce(t*2-d, 0, c, d) * .5 + c*.5 + b;
    }
};

// smooth scroll
var timer = null;
var smooth_scroll_to = function(elem, px) {
    if(timer != null) return;

    var startTime = Date.now();
    var begin = elem._scrollTop;
    var change = px - elem.scrollTop;

    timer = setInterval(function() {
        var time = Date.now() - startTime;
        elem._scrollTop = easingFunctions[config.easing](time, begin, change, config.duration);

        if(time >= config.duration) {
            elem._scrollTop = px;
            stop_scroll();
        }
    }, 5);
};
var stop_scroll = function() {
    if(timer != null) {
        clearInterval(timer);
        timer = null;
    }
};

// override scrollTop
var force_nonsmooth = false;
var current_to = 0;
var override_scrollTop = function(elem) {
    elem = elem.wrappedJSObject || elem;

    elem.__defineGetter__("_scrollTop", elem.__lookupGetter__("scrollTop"));
    elem.__defineSetter__("_scrollTop", elem.__lookupSetter__("scrollTop"));

    elem.__defineGetter__("scrollTop", function() { return elem._scrollTop; });
    elem.__defineSetter__("scrollTop", function(px) {
        // don't cancel if distination is same as current scroll
        if(px == current_to) return;

        stop_scroll();
        current_to = px;

        var diff = Math.abs(px - elem._scrollTop); 
        if(!force_nonsmooth && (
                config.type == "always" || 
                config.type == "auto" && diff > config.threshold
            ))
            smooth_scroll_to(elem, px);
        else
            elem._scrollTop = px;
    });
};
override_scrollTop(container);

// privent scroll when go to next feed
// override scrollTop of each items for fastladder_fixed_item_height.js
var register_hook = _w.register_hook;
register_hook("BEFORE_PRINTFEED", function() { force_nonsmooth = true; });
register_hook("BEFORE_SUBS_LOAD", function() { force_nonsmooth = true; });
register_hook("AFTER_PRINTFEED", function() {
    force_nonsmooth = false;
    Array.slice(container.getElementsByClassName("item")).map(override_scrollTop);
});
register_hook("AFTER_SUBS_LOAD", function() {
    force_nonsmooth = false;
    Array.slice(container.getElementsByClassName("item")).map(override_scrollTop);
});

window.addEventListener('load', function() {
    // Keybind
    var Keybind = _w.Keybind;

    // toggle smooth type
    var next_type = {
        none:   "always",
        always: "auto",
        auto:   "none"
    };
    Keybind.add("S", function() {
        config.type = next_type[config.type];
        _w.message('set smooth: "' + config.type + '"');

        if(_gm) window.setTimeout(function() { GM_setValue("type", config.type); }, 0);
    });

    // scroll to top
    Keybind.add("t", function() { container.scrollTop = 0; });

    // scroll to bottom
    Keybind.add("b", function() {
        var divs = container.getElementsByClassName("item");
        var last_item = divs[divs.length - 1];
        var target = last_item.offsetTop + last_item.offsetHeight
            - container.offsetHeight + 40;
        container.scrollTop = target;
    });
}, false);

})();