dw_scrollObj.prototype.bSizeDragBar = true;



dw_scrollObj.prototype.setUpScrollbar = function(id, trkId, axis, offx, offy) {

  if (!document.getElementById) return;

  var bar = document.getElementById(id);

  var trk = document.getElementById(trkId);

  dw_slidebar.init(bar, trk, axis, offx, offy);

  // connect dw_slidebar with dw_scrollObj

  bar.wn = dw_scrollObjs[this.id]; // scroll area object this bar connected to

  if (axis == "v") this.vBarId = id; else this.hBarId = id;

  // also called on_load (i.e., when layer loaded), but in case h and v scrollbars, need to call here too

  if (this.bSizeDragBar) this.setBarSize();

  bar.on_drag_start = bar.on_slide_start = dw_scrollObj.getWndoLyrRef;

  bar.on_drag_end =   bar.on_slide_end =   dw_scrollObj.tossWndoLyrRef;

  bar.on_drag =       bar.on_slide =       dw_scrollObj.UpdateWndoLyrPos;

}



// for these 3 functions (assigned to bar.on_drag/slide...) "this" refers to bar

// get/discard ref to layer visible in scroll area

dw_scrollObj.getWndoLyrRef = function()  { this.wnLyr = document.getElementById(this.wn.lyrId); }

dw_scrollObj.tossWndoLyrRef = function() { this.wnLyr = null; }

// keep position of scrolling layer in synch with slide/drag of bar

dw_scrollObj.UpdateWndoLyrPos = function(x, y) {

  var nx, ny;

  if (this.axis == "v") {

    nx = this.wn.x; // floating point values for loaded layer's position held in shiftTo method

    ny = -(y - this.minY) * ( this.wn.maxY / (this.maxY - this.minY) ) || 0;

  } else {

    ny = this.wn.y;

    nx = -(x - this.minX) * ( this.wn.maxX / (this.maxX - this.minX) ) || 0;

  }

  this.wn.shiftTo(this.wnLyr, nx, ny);

}



// Keep position of dragBar in sync with position of layer onscroll

dw_scrollObj.prototype.updateScrollbar = function(x, y) {

  var nx, ny;

  if ( this.vBarId ) {

    if (!this.maxY) return;

    ny = -( y * ( (this.vbar.maxY - this.vbar.minY) / this.maxY ) - this.vbar.minY );

    ny = Math.min( Math.max(ny, this.vbar.minY), this.vbar.maxY);  

    nx = parseInt(this.vbar.style.left);

    this.vbar.style.left = nx + "px"; this.vbar.style.top = ny + "px";

  } if ( this.hBarId ) {

    if (!this.maxX) return;

    nx = -( x * ( (this.hbar.maxX - this.hbar.minX) / this.maxX ) - this.hbar.minX );

    nx = Math.min( Math.max(nx, this.hbar.minX), this.hbar.maxX);

    ny = parseInt(this.hbar.style.top);

    this.hbar.style.left = nx + "px"; this.hbar.style.top = ny + "px";

  } 

  

}



// Restore dragBar to start position when loading new layer

dw_scrollObj.prototype.restoreScrollbars = function() {

  var bar;

  if (this.vBarId) {

    bar = document.getElementById(this.vBarId);

    bar.style.left = bar.minX + "px"; bar.style.top = bar.minY + "px";

  }

  if (this.hBarId) {

    bar = document.getElementById(this.hBarId);

    bar.style.left = bar.minX + "px"; bar.style.top = bar.minY + "px";

  }

}

  

// Size dragBar in proportion to size of content in layer

// called on_load of layer if bSizeDragBar prop true

dw_scrollObj.prototype.setBarSize = function() {

  var bar;

  var lyr = document.getElementById(this.lyrId);

  var wn = document.getElementById(this.id);

  if (this.vBarId) {

    bar = document.getElementById(this.vBarId);

    bar.style.height = (lyr.offsetHeight > wn.offsetHeight)? bar.trkHt / ( lyr.offsetHeight / wn.offsetHeight ) + "px": bar.trkHt - 2*bar.minY + "px";

    bar.maxY = bar.trkHt - bar.offsetHeight - bar.minY; 

  }

  if (this.hBarId) {

    bar = document.getElementById(this.hBarId);

    bar.style.width = (this.wd > wn.offsetWidth)? bar.trkWd / ( this.wd / wn.offsetWidth ) + "px": bar.trkWd - 2*bar.minX + "px";

    bar.maxX = bar.trkWd - bar.offsetWidth - bar.minX; 

  }

}



// called from load method

dw_scrollObj.prototype.on_load = function() { 

  this.restoreScrollbars();

  if (this.bSizeDragBar) this.setBarSize();

}



dw_scrollObj.prototype.on_scroll = dw_scrollObj.prototype.on_slide = function(x,y) { this.updateScrollbar(x,y); }



// obtain and discard references to relevant dragBar

dw_scrollObj.prototype.on_scroll_start = dw_scrollObj.prototype.on_slide_start = function() {

  if ( this.vBarId ) this.vbar = document.getElementById(this.vBarId);

  if ( this.hBarId ) this.hbar = document.getElementById(this.hBarId);

}



dw_scrollObj.prototype.on_scroll_end = dw_scrollObj.prototype.on_slide_end = function(x, y) { 

  this.updateScrollbar(x,y);

  this.lyr = null; this.bar = null; 

}