var dw_slidebar = {
  obj: null,
  slideDur: 500,  // duration of glide onclick of track  
  init: function (bar, track, axis, x, y) {
    x = x || 0; y = y || 0;
    bar.style.left = x + "px"; bar.style.top = y + "px";
    bar.axis = axis; track.bar = bar;
    if (axis == "h") {
      bar.trkWd = track.offsetWidth; // hold for setBarSize
      bar.maxX = bar.trkWd - bar.offsetWidth - x; 
      bar.minX = x; bar.maxY = y; bar.minY = y;
    } else {
      bar.trkHt = track.offsetHeight;
      bar.maxY = bar.trkHt - bar.offsetHeight - y; 
      bar.maxX = x; bar.minX = x; bar.minY = y;
    }
    bar.on_drag_start =  bar.on_drag =   bar.on_drag_end = 
    bar.on_slide_start = bar.on_slide =  bar.on_slide_end = function() {}
    bar.onmousedown = this.startDrag; track.onmousedown = this.startSlide;
  },
  
  startSlide: function(e) { // called onmousedown of track 
    if ( dw_slidebar.aniTimer ) clearInterval(dw_slidebar.aniTimer);
    e = e? e: window.event;
    var bar = dw_slidebar.obj = this.bar; // i.e., track's bar
    e.offX = (typeof e.layerX != "undefined")? e.layerX: e.offsetX;
    e.offY = (typeof e.layerY != "undefined")? e.layerY: e.offsetY;
    bar.startX = parseInt(bar.style.left); bar.startY = parseInt(bar.style.top);
    if (bar.axis == "v") {
      bar.destX = bar.startX;
      bar.destY = (e.offY < bar.startY)? e.offY: e.offY - bar.offsetHeight;
      bar.destY = Math.min( Math.max(bar.destY, bar.minY), bar.maxY );
    } else {
      bar.destX = (e.offX < bar.startX)? e.offX: e.offX - bar.offsetWidth;
      bar.destX = Math.min( Math.max(bar.destX, bar.minX), bar.maxX );
      bar.destY = bar.startY;
    }
    bar.distX = bar.destX - bar.startX; bar.distY = bar.destY - bar.startY;
    dw_slidebar.per = Math.PI/(2 * dw_slidebar.slideDur);
  	dw_slidebar.slideStart = (new Date()).getTime();
    bar.on_slide_start(bar.startX, bar.startY);
  	dw_slidebar.aniTimer = setInterval("dw_slidebar.doSlide()",10);
  },
  
  doSlide: function() {
    if ( !dw_slidebar.obj ) { clearInterval(dw_slidebar.aniTimer); return; }    
    var bar = dw_slidebar.obj;     
    var elapsed = (new Date()).getTime() - this.slideStart;
  	if (elapsed < this.slideDur) {
  		var x = bar.startX + bar.distX * Math.sin(this.per*elapsed);
  		var y = bar.startY + bar.distY * Math.sin(this.per*elapsed);
      bar.style.left = x + "px"; bar.style.top = y + "px";
      bar.on_slide(x, y);
  	} else {	// if time's up
      clearInterval(this.aniTimer);
      bar.style.left = bar.destX + "px"; bar.style.top = bar.destY + "px";
      bar.on_slide_end(bar.destX, bar.destY);
      this.obj = null;
  	}
  },
  
  startDrag: function (e) { // called onmousedown of bar 
    e = dw_event.DOMit(e);
    if ( dw_slidebar.aniTimer ) clearInterval(dw_slidebar.aniTimer);
    var bar = dw_slidebar.obj = this;
    bar.downX = e.clientX; bar.downY = e.clientY;
    bar.startX = parseInt(bar.style.left);
    bar.startY = parseInt(bar.style.top);
    bar.on_drag_start(bar.startX, bar.startY);
    dw_event.add( document, "mousemove", dw_slidebar.doDrag, true );
    dw_event.add( document, "mouseup",   dw_slidebar.endDrag,  true );
    e.stopPropagation();
  },

  doDrag: function (e) {
    e = e? e: window.event;
    if (!dw_slidebar.obj) return;
    var bar = dw_slidebar.obj; 
    var nx = bar.startX + e.clientX - bar.downX;
    var ny = bar.startY + e.clientY - bar.downY;
    nx = Math.min( Math.max( bar.minX, nx ), bar.maxX);
    ny = Math.min( Math.max( bar.minY, ny ), bar.maxY);
    bar.style.left = nx + "px"; bar.style.top  = ny + "px";
    bar.on_drag(nx,ny);
    return false;  
  },
  
  endDrag: function () {
    dw_event.remove( document, "mousemove", dw_slidebar.doDrag, true );
    dw_event.remove( document, "mouseup",   dw_slidebar.endDrag,  true );
    if ( !dw_slidebar.obj ) return; // avoid errors in ie if inappropriate selections
    dw_slidebar.obj.on_drag_end( parseInt(dw_slidebar.obj.style.left), parseInt(dw_slidebar.obj.style.top) );
    dw_slidebar.obj = null;  
  }
  
}