var obsahViditelneH;
var scrollActH;
var scrollH;
var topAct;
var scroll_timer=false;

function start() {
	obsahViditelneH = 160;
	scrollActH = 0;
	if(document.getElementById("obsah")) {
		topAct = parseInt(document.getElementById("obsah").style['top']);
		scrollH = parseInt(document.getElementById("obsah").offsetHeight);
		}
	else {
		if(document.all) {
			topAct = parseInt(document.all.obsah.style['top']);
			scrollH = parseInt(document.all.obsah.scrollHeight);
			}
		}
	if(scrollH > obsahViditelneH) sipky("sipka_dolu","1");
	else sipky("sipka_dolu","0");
	}

function scroll(smer) {
	if(!smer) smer="dolu";
	if(smer=="dolu" && (scrollActH < (scrollH-obsahViditelneH))) {
		//Jedeme z kopce
		sipky("sipka_dolu","1"); sipky("sipka_nahoru","1");
		scrollActH++; topAct--;
		clip_new = "rect("+scrollActH+"px 400px "+(scrollActH+obsahViditelneH)+"px 0px)";
		top_new = topAct + "px";
		if(document.getElementById("obsah")) {
			document.getElementById("obsah").style.clip=clip_new;
			document.getElementById("obsah").style.top=top_new;
			}
		else {
			if(document.all) {
				document.all.obsah.style.clip=clip_new;
				document.all.obsah.style.top=top_new;
				}
			}
		scroll_timer=setTimeout("scroll('"+smer+"')",20);
		}
	if(smer=="nahoru" && (scrollActH > 0)) {
		//Jedeme nahoru
		sipky("sipka_nahoru","1"); sipky("sipka_dolu","1");
		scrollActH--; topAct++;
		clip_new = "rect("+scrollActH+"px 400px "+(scrollActH+obsahViditelneH)+"px 0px)";
		top_new = topAct + "px";
		document.getElementById("obsah").style.clip=clip_new;
		document.getElementById("obsah").style.top=top_new;
		scroll_timer=setTimeout("scroll('"+smer+"')",20);
		}
	if(smer=="dolu" && (scrollActH == (scrollH-obsahViditelneH))) {
		if(scroll_timer) clearTimeout(scroll_timer);
		sipky("sipka_dolu","0"); sipky("sipka_nahoru","1");
		}
	if(smer=="nahoru" && (scrollActH == 0)) {
		if(scroll_timer) clearTimeout(scroll_timer);
		sipky("sipka_nahoru","0"); if(scrollH > obsahViditelneH) sipky("sipka_dolu","1");
		}
	}

function scroll_stop() {
	if(scroll_timer) clearTimeout(scroll_timer);
	}

function sipky(smer,vypln) {
	cesta=document.images[smer].src;
	nemenna=cesta.substr(0,cesta.length-5);
	novaCesta=nemenna+vypln+".gif";
	if(novaCesta!=cesta) document.images[smer].src=novaCesta;
}

onload = start;