function Scroller(startPos, dispCnt)
{
	this.idArrays = null;
	this.dispCnt = dispCnt;
	this.startPos = startPos;
}

Scroller.prototype.goPrev = function() {
	this.startPos = this.startPos - 1;
	if(this.startPos < 0) {
		this.startPos = 0;	
	}	
	
	var endPos = this.startPos + this.dispCnt;
	if(endPos > this.idArrays.length) {
		endPos = this.idArrays.length;
	}

	for(i=0; i<this.idArrays.length; i++) {
		var el = document.getElementById(this.idArrays[i]);
		el.style.display = 'none';
	}
	
	for(i=this.startPos; i<endPos; i++) {
		var el = document.getElementById(this.idArrays[i]);
		el.style.display = 'block';
	}			
}

Scroller.prototype.goNext = function() {
	if(this.startPos < 0) {
		this.startPos = 0;	
	}	
	
	this.startPos = this.startPos + 1;
	
	var endPos = this.startPos + this.dispCnt;
	if(endPos > this.idArrays.length) {
		this.startPos = this.startPos - 1;
		endPos = this.idArrays.length;
	}				

	for(i=0; i<this.idArrays.length; i++) {
		var el = document.getElementById(this.idArrays[i]);
		el.style.display = 'none';
	}
	
	for(i=this.startPos; i<endPos; i++) {
		var el = document.getElementById(this.idArrays[i]);
		el.style.display = 'block';
	}				
}	

Scroller.prototype.setDisp = function(startIdx, endIdx) {
	var stdIdx = startIdx;
	var edIdx = endIdx;
	if(stdIdx < 0) {
		stdIdx = 0;
	}
	if(edIdx > this.idArrays.length - 1) {
		edIdx = this.idArrays.length - 1;
	}
	if(stdIdx > edIdx) {
		return;
	}
	else {
		for(i=0; i<this.idArrays.length; i++) {
			var el = document.getElementById(this.idArrays[i]);
			el.style.display = 'none';
		}
		
		for(i=stdIdx; i<=edIdx; i++) {
			var el = document.getElementById(this.idArrays[i]);
			el.style.display = 'block';
		}	
	}
}

Scroller.prototype.add = function(elemId)
{
	if(this.idArrays == null) {
		this.idArrays = new Array();
	}
	
	this.idArrays[this.idArrays.length] = elemId;
	
	if(this.idArrays.length - 1 < this.startPos || this.idArrays.length > (this.startPos + this.dispCnt)) {
			var el = document.getElementById(elemId);
			el.style.display = 'none';
	}
}