// レイヤをスクロールによって制御する

//ブラウザのバージョンをチェックする
function verifyCompatibleBrowser(){ 
    this.ver = navigator.appVersion ;
    this.dom = document.getElementById ? 1 : 0 ;
	this.ie5 = (navigator.userAgent.indexOf("MSIE 5")>-1 && this.dom) ? 1 : 0 ;
    this.ie4 = (document.all && !this.dom)?1:0 ;
    this.ns5 = (this.dom && parseInt(this.ver) >= 5) ? 1 : 0 ;
    this.ns4 = (document.layers && !this.dom) ? 1 : 0 ; 
    this.bw = (this.ie5 || this.ie4 || this.ns4 || this.ns5) ;
    return this ;
} 
bw=new verifyCompatibleBrowser() ;

var initialised ;
function InitialiseScrollableArea(){ 
    objContainer = new ConstructObject('outLayer') ;
    objScroller = new ConstructObject('innerLayer','outLayer') ;
    objScroller.MoveArea(0,0) ;
    objContainer.css.visibility = 'visible' ;
    initialised = true ;
} 
 
var speed = 80 ;
var loop, timer ;
 
function ConstructObject(obj,nest){ 
    nest=(!nest) ? '' : 'document.'+nest+'.' ;
	
    this.el = bw.dom ? document.getElementById(obj) : bw.ie4 ? document.all[obj] : bw.ns4 ? eval(nest+'document.'+obj) : 0 ;
    this.css = bw.dom ? document.getElementById(obj).style:bw.ie4 ? document.all[obj].style:bw.ns4 ? eval(nest+'document.'+obj) : 0 ;
    this.scrollHeight = bw.ns4 ? this.css.document.height : this.el.offsetHeight ;
    this.clipHeight = bw.ns4 ? this.css.clip.height : this.el.offsetHeight ;
    this.up = MoveAreaUp ;
	this.down = MoveAreaDown ;
    this.MoveArea = MoveArea ;
	this.x ;
	this.y ; 
    this.obj = obj + "Object" ;
    eval(this.obj + "=this") ;
    return this ;
}

function MoveArea(x,y){ 
    this.x = x ;
	this.y = y ;
    this.css.left = this.x ; 
    this.css.top = this.y ;
} 
 
function MoveAreaDown(move){ 
	if(this.y>-this.scrollHeight+objContainer.clipHeight){ 
    	this.MoveArea(0,this.y-move) ;
    	if(loop) {
			setTimeout(this.obj+".down("+move+")",speed) ;
		}
	}
}

function MoveAreaUp(move){ 
	if(this.y<0){ 
    	this.MoveArea(0,this.y-move) ;
    	if(loop) {
			setTimeout(this.obj+".up("+move+")",speed) ;
		}
	}
}

function PerformScroll(speed){ 
	if(initialised){ 
		loop = true ; 
		if(speed>0) objScroller.down(speed) ;
		else objScroller.up(speed) ;
	}
}

function CeaseScroll(){ 
    loop = false ;
    if(timer) clearTimeout(timer) ;
}