/***
 *
 * gs.js
 * "JavaScript OO Vector Graphics Package"
 * from http://www.webreference.com/programming/javascript/gr/column2/index.html
 *
 ***/

function Graphics(canvas)
{
  this.canvas = canvas;
  this.cache = new Array;
  this.shapes = new Object;
  this.nObject = 0;

  // defaults
  this.penColor = "black";
  this.zIndex = 1;
}

Graphics.prototype.createPlotElement = function(x,y,w,h) 
{
  // detect canvas
  if ( !this.oCanvas )
  {
    if ( (this.canvas == undefined) || (this.canvas == "") ) 
      this.oCanvas = document.body;
    else 
      this.oCanvas = document.getElementById(this.canvas);
  }

  // retrieve DIV
  var oDiv;
  if ( this.cache.length )
    oDiv = this.cache.pop();
  else 
  {
    oDiv = document.createElement('div');
    this.oCanvas.appendChild(oDiv);

    oDiv.style.position = "absolute";
    oDiv.style.margin = "0px";
    oDiv.style.padding = "0px";
    oDiv.style.overflow = "hidden";
    oDiv.style.border = "0px";
  }

  // set attributes
  oDiv.style.zIndex = this.zIndex;
  oDiv.style.backgroundColor = this.penColor;
  
  oDiv.style.left = x + 'px';
  oDiv.style.top = y + 'px';
  oDiv.style.width = w + "px";
  oDiv.style.height = h + "px";

  oDiv.style.visibility = "visible";
  
  return oDiv;
}

Graphics.prototype.releasePlotElement = function(oDiv)
{
  oDiv.style.visibility = "hidden";
  this.cache.push(oDiv);
}

Graphics.prototype.addShape = function(shape)
{
  shape.oGraphics = this;
  shape.graphicsID = this.nObject;
  this.shapes[this.nObject] = shape;
  this.nObject++;
  shape.draw();
  return shape;
}

Graphics.prototype.removeShape = function(shape)
{
  if ( (shape instanceof Object) && 
    (shape.oGraphics == this) && 
    (this.shapes[shape.graphicsID] == shape) )
  {
    shape.undraw();
    this.shapes[shape.graphicsID] = undefined;
    shape.oGraphics = undefined;
  }
}

Graphics.prototype.clear = function()
{
  for ( var i in this.shapes )
    this.removeShape(this.shapes[i]);
}

//=============================================================================
// Point
Graphics.prototype.drawPoint = function(x,y)
{
  return this.addShape(new Point(x,y))
}

function Point(x,y)
{
  this.x = x;
  this.y = y;
}
Point.prototype.draw = function()
{
  this.oDiv = this.oGraphics.createPlotElement(this.x,this.y,1,1);
}
Point.prototype.undraw = function()
{
  this.oGraphics.releasePlotElement(this.oDiv);
  this.oDiv = undefined;
}

//=============================================================================
// Line
Graphics.prototype.drawLine = function(x1,y1,x2,y2)
{
  return this.addShape(new Line(x1,y1,x2,y2))
}

function Line(x1,y1,x2,y2)
{
  this.x1 = x1;
  this.y1 = y1;
  this.x2 = x2;
  this.y2 = y2;
}

Line.prototype.draw = function()
{
  this.plots = new Array;

  var dx = this.x2 - this.x1;
  var dy = this.y2 - this.y1;
  var x = this.x1;
  var y = this.y1;

  var n = Math.max(Math.abs(dx),Math.abs(dy));
  dx = dx / n;
  dy = dy / n;
  for ( i = 0; i <= n; i++ )
  {
    this.plots.push(this.oGraphics.createPlotElement(Math.round(x),Math.round(y),1,1));

    x += dx;
    y += dy;
  }
}
Line.prototype.undraw = function()
{
  while ( this.plots.length )
    this.oGraphics.releasePlotElement(this.plots.pop());
  this.plots = undefined;
}

//=============================================================================
// Circle
Graphics.prototype.drawCircle = function(x,y,r)
{
  return this.addShape(new Circle(x,y,r))
}

function Circle(x,y,r)
{
  this.x = x;
  this.y = y;
  this.radius = r;
}

Circle.prototype.draw = function()
{
  this.plots = new Array;

  var r2 = this.radius * this.radius;
  var x = 0;
  var y = this.radius;

  while ( x <= y )
  {
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x + x), Math.round(this.y + y), 1, 1));
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x - x), Math.round(this.y + y), 1, 1));
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x + x), Math.round(this.y - y), 1, 1));
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x - x), Math.round(this.y - y), 1, 1));
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x + y), Math.round(this.y + x), 1, 1));
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x + y), Math.round(this.y - x), 1, 1));
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x - y), Math.round(this.y + x), 1, 1));
    this.plots.push(this.oGraphics.createPlotElement(Math.round(this.x - y), Math.round(this.y - x), 1, 1));

    x++;
    y = Math.round(Math.sqrt(r2 - x*x));
  }
}
Circle.prototype.undraw = Line.prototype.undraw;

//=============================================================================
// Rectangle
Graphics.prototype.drawRectangle = function(x,y,w,h)
{
  return this.addShape(new Rectangle(x,y,w,h))
}

function Rectangle(x,y,w,h)
{
  this.x = x;
  this.y = y;
  this.w = w;
  this.h = h;
}

Rectangle.prototype.draw = function()
{
  this.plots = new Array;
  this.plots.push(this.oGraphics.createPlotElement(this.x, this.y, this.w, 3));
  this.plots.push(this.oGraphics.createPlotElement(this.x, this.y, 3, this.h));
  this.plots.push(this.oGraphics.createPlotElement(this.x + this.w - 3, this.y, 3, this.h));
  this.plots.push(this.oGraphics.createPlotElement(this.x, this.y + this.h - 3, this.w, 3));
}

Rectangle.prototype.undraw = function()
{
  while (this.plots.length)
    this.oGraphics.releasePlotElement(this.plots.pop());
  this.plots = undefined;
}

//=============================================================================

//=============================================================================
// FillRectangle
Graphics.prototype.fillRectangle = function(x,y,w,h)
{
  return this.addShape(new FillRectangle(x,y,w,h))
}

function FillRectangle(x,y,w,h)
{
  this.x = x;
  this.y = y;
  this.w = w;
  this.h = h;
}

FillRectangle.prototype.draw = function()
{
  this.oDiv = this.oGraphics.createPlotElement(this.x,this.y,this.w,this.h);
}
FillRectangle.prototype.undraw = Point.prototype.undraw;