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Auto Scroll Mouse

No mousewheel? No problem! This script will scroll the page if you place your mouse near the top or bottom of the window and wiggle it.

当前为 2018-04-25 提交的版本，查看 最新版本。

// Marc Belmont presents : Auto Scroll!
// version 1.6
// 2006-10-09
//
// Tweaked by joeytwiddle
//
// ==UserScript==
// @name          Auto Scroll Mouse
// @namespace     http://www.marcbelmont.com
// @description   No mousewheel?  No problem!  This script will scroll the page if you place your mouse near the top or bottom of the window and wiggle it.
// @version       2.1.4
// @license       ISC
// @include       http://*/*
// @include       https://*/*
// ==/UserScript==

//////////////////////
// Constants	    //
//////////////////////

var NOSCROLL_PERCENT = 50; // Area in the middle of the page where there won't be scrolling
var SCROLLSTEP = 5; // Scrolling speed
var ONLYLEFTRIGHT = 1; // Scrolling will happen only when you move left or right in the top or bottom areas. Possible values are 0 | 1
var ONLYLEFTRIGHT_MOUSESPEED = 1.5; // Mouse speed needed to activate the scrolling
var ONLYLEFTRIGHT_DONTSCROLL = 100; // if no event for too long, no scrolling
var DELAY_TIME = 5; // This tries to reduce the number of scroll operations, to reduce load on the browser

//////////////////////
// Some Code	    //
//////////////////////

var _mX = 0;
var _mXOld = 0;
var _mYOld = 0;
var _mY = 0;
var _go = 0;
var _mNow = new Date();
var _mThen = new Date();

// 2. scroll the window
function ScrollWindow() {
  // don't scroll if we're in the middle of the page
  var end = ((_mY - window.pageYOffset) - window.innerHeight/2);
  if (Math.abs(end) < window.innerHeight*NOSCROLL_PERCENT/200) {
    return;
  }
  /* var down = (_mY - window.pageYOffset) / window.innerHeight;
  if (Math.abs(down - 0.5)*2 < NOSCROLL_PERCENT/100) {
    return;
  } */

  // if ONLYLEFTRIGHT is on, scroll only when you move left or right,
  if (ONLYLEFTRIGHT && (Math.abs(_mY - _mYOld) > 2)) {
    return;
  }
  // if you want scrolling, mouse have to go start moving slowly
  if (Math.abs(_mY - _mYOld) < 7 && Math.abs(_mX - _mXOld) < 7)
    _go = 1;


  // scroll the page
  var way = end > 0 ? 1 : -1;
  var val = SCROLLSTEP;
  if (ONLYLEFTRIGHT) {
    if (_go) {
      val = Math.pow(Math.abs(_mX - _mXOld), ONLYLEFTRIGHT_MOUSESPEED);
    } else {
      val = 0;
    }
  }
  if (val != 0) {
    window.scrollTo(window.pageXOffset, window.pageYOffset + val*way);
  }
}

function maybe(scrollWindow) {
  var timer;
  return function(){
    if (!timer) {
      timer = setTimeout(function(){
        timer = null;
        scrollWindow();
        _mXOld = _mX;
        _mYOld = _mY;
        _mThen = _mNow;
      }, DELAY_TIME);
    }
  };
}

var maybeScrollWindow = maybe(ScrollWindow);

// 1. Catch mouse movement
document.addEventListener('mousemove', mousemove, true);
function mousemove(e)
{
  // get mouse pos and the date
  if (!e)
    var e = window.event || window.Event;
  if('undefined'!=typeof e.pageX) {
    _mX = e.pageX;
    _mY = e.pageY;
  } else {
    _mX = e.clientX + document.body.scrollLeft;
    _mY = e.clientY + document.body.scrollTop;
  }
  _mNow = Date.now();

  // Hack to avoid unwanted scrolling when the mouse enters a window
  // if no event for too long, no scrolling
  if (_mNow - _mThen > ONLYLEFTRIGHT_DONTSCROLL)
    _go = 0;

  // Scroll the window
  maybeScrollWindow();
}