/* ***********************************************************
Example 4-3 (DHTMLAPI.js)
"Dynamic HTML:The Definitive Reference"
2nd Edition
by Danny Goodman
Published by O'Reilly & Associates  ISBN 1-56592-494-0
http://www.oreilly.com
Copyright 2002 Danny Goodman.  All Rights Reserved.
************************************************************ */
// DHTMLapi.js custom API for cross-platform
// object positioning by Danny Goodman (http://www.dannyg.com).
// Release 2.0. Supports NN4, IE, and W3C DOMs.

// Global variables
var isCSS, isW3C, isIE4, isNN4, isIE6CSS;

// Initialize upon load to let all browsers establish content objects
function initDHTMLAPI()
{
   if(document.images)
   {
      isCSS = (document.body && document.body.style) ? true : false;
      isW3C = (isCSS && document.getElementById) ? true : false;
      isIE4 = (isCSS && document.all) ? true : false;
      isNN4 = (document.layers) ? true : false;
      isIE6CSS = (document.compatMode && document.compatMode.indexOf("CSS1") >= 0) ? true : false;
   }
}

// Set event handler to initialize API
window.onload = initDHTMLAPI;

// Seek nested NN4 layer from string name
function seekLayer(doc, name)
{
   var theObj;
   for(var i = 0; i < doc.layers.length; i++)
   {
      if(doc.layers[i].name == name)
      {
         theObj = doc.layers[i];
         break;
      }

      // dive into nested layers if necessary
      if(doc.layers[i].document.layers.length > 0)
         theObj = seekLayer(document.layers[i].document, name);
   }

   return theObj;
}

// Convert object name string or object reference
// into a valid element object reference
function getRawObject(obj)
{
   // the default action is to pass through object reference
   var theObj = obj;

   if(typeof obj == "string")
   {
      if(isW3C)
         theObj = document.getElementById(obj);
      else if(isIE4)
         theObj = document.all(obj);
      else if(isNN4)
         theObj = seekLayer(document, obj);
   }

   return theObj;
}

// Convert object name string or object reference
// into a valid style (or NN4 layer) reference
function getObject(obj)
{
   var theObj = getRawObject(obj);
   
   if(theObj && isCSS) 
      theObj = theObj.style;
   
   return theObj;
}

// Position an object at a specific pixel coordinate
function shiftTo(obj, x, y)
{
   var theObj = getObject(obj);
   
   if(theObj) 
   {
      if(isCSS) 
      {
         // equalize incorrect numeric value type
         var units = (typeof theObj.left == "string") ? "px" : 0;
         
         theObj.left = x + units;
         theObj.top = y + units;
      }
      else if(isNN4) 
         theObj.moveTo(x,y);
   }
}

// Move an object by x and/or y pixels
function shiftBy(obj, deltaX, deltaY)
{
   var theObj = getObject(obj);

   if(theObj)
   {
      if(isCSS)
      {
         // equalize incorrect numeric value type
         var units = (typeof theObj.left == "string") ? "px" : 0;
         
         theObj.left = getObjectLeft(obj) + deltaX + units;
         theObj.top = getObjectTop(obj) + deltaY + units;
      }
      else if(isNN4)
         theObj.moveBy(deltaX, deltaY);
   }
}

// Set the z-order of an object
function setZIndex(obj, zOrder)
{
   var theObj = getObject(obj);
   
   if(theObj)
      theObj.zIndex = zOrder;
}

// Set the background color of an object
function setBGColor(obj, color)
{
   var theObj = getObject(obj);
   
   if(theObj)
   {
      if(isNN4)
         theObj.bgColor = color;
      else if(isCSS)
         theObj.backgroundColor = color;
   }
}

// Set the visibility of an object to visible
function show(obj)
{
   var theObj = getObject(obj);

   if(theObj)
      theObj.visibility = "visible";
}

// Set the visibility of an object to hidden
function hide(obj)
{
   var theObj = getObject(obj);
   
   if(theObj)
      theObj.visibility = "hidden";
}

// Retrieve the x coordinate of a positionable object
function getObjectLeft(obj)
{
   var result = 0;
   var elem = getRawObject(obj);
   
   if(document.defaultView)
   {
      var style = document.defaultView;
      var cssDecl = style.getComputedStyle(elem, "");
      result = cssDecl.getPropertyValue("left");
   }
   else if(elem.currentStyle)
      result = elem.currentStyle.left;
   else if(elem.style)
      result = elem.style.left;
   else if(isNN4)
      result = elem.left;
   
   return parseInt(result);
}

// Retrieve the y coordinate of a positionable object
function getObjectTop(obj) 
{
   var result = 0;
   var elem = getRawObject(obj);
   
   if(document.defaultView)
   {
      var style = document.defaultView;
      var cssDecl = style.getComputedStyle(elem, "");
      result = cssDecl.getPropertyValue("top");
   }
   else if(elem.currentStyle)
      result = elem.currentStyle.top;
   else if(elem.style)
      result = elem.style.top;
   else if(isNN4)
      result = elem.top;
   
   return parseInt(result);
}

// Retrieve the rendered width of an element
function getObjectWidth(obj)
{
   var result = 0;
   var elem = getRawObject(obj);
   
   if(elem.offsetWidth)
      result = elem.offsetWidth;
   else if(elem.clip && elem.clip.width)
      result = elem.clip.width;
   else if(elem.style && elem.style.pixelWidth)
      result = elem.style.pixelWidth;
   
   return parseInt(result);
}

// Retrieve the rendered height of an element
function getObjectHeight(obj)
{
   var result = 0;
   var elem = getRawObject(obj);
   
   if(elem.offsetHeight)
      result = elem.offsetHeight;
   else if(elem.clip && elem.clip.height)
      result = elem.clip.height;
   else if(elem.style && elem.style.pixelHeight)
      result = elem.style.pixelHeight;
   
   return parseInt(result);
}

// Return the available content width space in browser window
function getInsideWindowWidth()
{
   if(window.innerWidth)
      return window.innerWidth;
   else if(isIE6CSS) // measure the html element's clientWidth      
      return document.body.parentElement.clientWidth;
   else if(document.body && document.body.clientWidth)
      return document.body.clientWidth;
   
   return 0;
}

// Return the available content height space in browser window
function getInsideWindowHeight()
{
   if(window.innerHeight)
      return window.innerHeight;
   else if(isIE6CSS) // measure the html element's clientHeight
      return document.body.parentElement.clientHeight;
   else if(document.body && document.body.clientHeight) 
      return document.body.clientHeight;
   
   return 0;
}