document.onmousedown = start_scrolling;
  
function start_scrolling(ereignis){
  if(!ereignis) {
    ereignis = window.event;
  }
 
   	innerFrameWidth = document.getElementById('image_table').offsetWidth;
//  innerFrameWidth = document.getElementById('image_frame').scrollWidth; //Problem mit Opera, der hier die max #3fff anzeigt
  frameWidth = document.getElementById('photo_frame').offsetWidth;

  interfaceContainerLeft = document.getElementById('container').offsetLeft;
  interfaceContainerTop = document.getElementById('container').offsetTop;
  photoNavContainerLeft = document.getElementById('photo_nav').offsetLeft;
  photoNavContainerTop = document.getElementById('photo_nav').offsetTop;
  if(document.compatMode && document.compatMode!="BackCompat") {
	pageX = document.documentElement.scrollLeft;//Scrollversatz;
	pageY = document.documentElement.scrollTop;//Scrollversatz;
  } else {
	pageX = window.pageXOffset;
	pageY = window.pageYOffset;
  }
  positionLeft = interfaceContainerLeft+photoNavContainerLeft - pageX; //- Scrollversatz
  positionTop = interfaceContainerTop+photoNavContainerTop - pageY;

  if(ereignis.clientX>positionLeft+31 && ereignis.clientX<positionLeft+311+18
    && ereignis.clientY>positionTop && ereignis.clientY<positionTop+18) { //18=Triggerhöhe/breite
	//=>trigger ziehen
    trigger = document.getElementById('photo_nav_trigger').style;
    scrolling = document.getElementById('photo_nav_trigger');

    trigger.left = ereignis.clientX-positionLeft-8;
    scrolling.position = ereignis.clientX-positionLeft-40;

    if(ereignis.clientX-positionLeft-8<31)
      trigger.left = 31;
    if(ereignis.clientX-positionLeft-8>311)
      trigger.left = 311; 
	  
    if(ereignis.clientX-positionLeft-8>31
      && ereignis.clientX-positionLeft-8<331) { //-8>31
      document.getElementById('image_frame').style.left = -(scrolling.position*((innerFrameWidth-frameWidth)/283)); //189 275
    }
    document.onmousemove = start_scrolling;
   return false;
  }

}

function stop_scrolling(){
  document.onmousemove = null;
  return false;
}

  function in_array(value,array) {
    for(var i=0;i<array.length;i++) {
      if(array[i] == value) {
        return true;
      }
    }
  }

function next_block() {
  triggerLeft = document.getElementById('photo_nav_trigger').offsetLeft;
  imageFrameLeft = document.getElementById('image_frame').offsetLeft;
  numBlocks = Math.ceil((innerFrameWidth)/1000-1); //678 = 608 +70 //930+70 = Seitenbreite
  oneBlockLeftPx = 283/ numBlocks; //189 Breite Nav-Bar+ halbe Breite Trigger = Schrittweite Trigger

  if(-(innerFrameWidth-1000)<imageFrameLeft-5 || imageFrameLeft == 0) {
      numFrameBlocks = Math.ceil((imageFrameLeft-2)/1000)-1;
      newImageFrameLeft = numFrameBlocks*1000;
	  document.getElementById('image_frame').style.left = newImageFrameLeft+ 'px';
      numFrameBlocks = -numFrameBlocks;
      document.getElementById('photo_nav_trigger').style.left = (Math.round(oneBlockLeftPx*numFrameBlocks))+30; //+Nulllinie Navbar
  }
}

function pref_block() {
  imageFrameLeft = document.getElementById('image_frame').offsetLeft+1;
  numBlocks = Math.ceil((innerFrameWidth)/1000-1);
  oneBlockLeftPx = 283/ numBlocks;

  if(imageFrameLeft < -1) { 
	  numFrameBlocks = (Math.floor(imageFrameLeft/1000))+1;
      newImageFrameLeft = numFrameBlocks*1000;

	  if(newImageFrameLeft>0) {
      newImageFrameLeft = 0;
	  oneBlockLeftPx = 0;
	  }
      document.getElementById('image_frame').style.left = newImageFrameLeft+ 'px';
      numFrameBlocks = -numFrameBlocks;
      document.getElementById('photo_nav_trigger').style.left = Math.round(oneBlockLeftPx*numFrameBlocks)+30;//+(11*numFrameBlocks); //30=Nulllinie Navbar
  }
}