http://ranger.uta.edu/~weems/NOTES3302/LAB/15SUM/LAB4/lab4.js

    draw: function (x,y) {
  // Draw background grid
      ctx=graphic.getContext('2d');
      ctx.textAlign="center";
      ctx.font="14px Geneva";
      ctx.clearRect(0,0,graphic.width,graphic.height);
      ctx.beginPath();
      for (var i=20;i<graphic.width;i+=20) {
        ctx.moveTo(i,0);
        ctx.lineTo(i,graphic.height);
        ctx.moveTo(0,i);
        ctx.lineTo(graphic.width,i);
        }
      ctx.strokeStyle="gray";
      ctx.lineWidth=1;
      ctx.stroke();

      for (var i=0;i<instance.length;i++)
        instance[i].draw(i,x,y);
      },
    drawLine: function (x0,y0,x1,y1,color) {


    draw: function (x,y) {

      . . .

      if (x==undefined || y==undefined) // No cursor position
        for (var i=0;i<instance.length;i++)
          //instance[i].draw(i,x,y);
          instance[i].draw(i,false);
      else {
        // Find indices of objects containing cursor position

        // Sort by ascending object area

        // Throw away objects containing other objects

        // Build simple table of indicators for highlighting

        for (var i=0;i<instance.length;i++)
          instance[i].draw(i,highlighted[i]);
        }
      },
    drawLine: function (x0,y0,x1,y1,color) {