/***************************************************************************
 This code is from Dynamic Web Coding at www.dyn-web.com
 Copyright 2004 by Sharon Paine 
 See Terms of Use at www.dyn-web.com/bus/terms.html
 regarding conditions under which you may use this code.
 This notice must be retained in the code as is!
****************************************************************************/

/*
 dw_scroll_aux.js  version date: May 2004 
 integrates scrolling layers code with scrollbar code (dw_scrollbar.js)
*/

// Size dragBar according to layer size? 
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; 
}