function Overlay(element)
{
  Module.call(this);
  
  this.element = element;
  
  // Module
  
  this.passive = function(cmd)
  {
    this.draw(cmd.position(),cmd.rect());
  }
  
  this.active = function(cmd)
  {
    if(cmd.bang()){ this.guides = []; }
  }
  
  this.hint = function(cmd)
  {
    if(cmd.bang()){ return "Overlay: Erase all guides"; }
    
    var hint_position = (cmd.position() ? "Position "+cmd.position().x+","+cmd.position().y+" " : "");
    var hint_rect = (cmd.rect() ? "Size "+cmd.rect().width+"px by "+cmd.rect().height+"px " : "");
    
    return "Overlay: "+hint_position+hint_rect;
  }
  
  // draw
  
  this.draw = function(position,rect)
  {
    this.clear();
    
    if(!position){ return; }
    
    if(rect){
      this.draw_rect(position,rect);
    }
    else if(position.x != 0 && position.y != 0){
      this.draw_pointer(position);
    }
    else if(position.x != 0 ){
      this.draw_vertical_line(position);
    }
    else if(position.y != 0 ){
      this.draw_horizontal_line(position);
    }
  }
  
  this.draw_rect = function(position,rect)
  {
    this.context().beginPath();
    
    position.normalize(rect);
    
    this.context().moveTo(position.x,position.y);
    this.context().lineTo(position.x + rect.width,position.y);
    this.context().lineTo(position.x + rect.width,position.y + rect.height);
    this.context().lineTo(position.x,position.y + rect.height);
    this.context().lineTo(position.x,position.y);
    
    this.context().lineCap="round";
    this.context().lineWidth = 1;
    this.context().strokeStyle = "#ff0000";
    this.context().stroke();
    this.context().closePath();
  }
  
  this.draw_pointer = function(position)
  {
    this.context().beginPath();
    
    this.context().moveTo(position.x,position.y);
    this.context().lineTo(position.x + 10,position.y);
    this.context().lineTo(position.x,position.y + 10);
    this.context().lineTo(position.x,position.y);
    
    this.context().lineCap="round";
    this.context().lineWidth = 1;
    this.context().strokeStyle = "#ff0000";
    this.context().stroke();
    this.context().closePath();
  }
  
  this.draw_vertical_line = function(position)
  {
    this.context().beginPath();
    
    this.context().moveTo(position.x,0);
    this.context().lineTo(position.x,this.element.height);
    
    this.context().lineCap="round";
    this.context().lineWidth = 1;
    this.context().strokeStyle = "#ff0000";
    this.context().stroke();
    this.context().closePath();
  }
  
  this.draw_horizontal_line = function(position)
  {
    this.context().beginPath();
    
    this.context().moveTo(position.x,0);
    this.context().lineTo(position.x,this.element.height);
    
    this.context().lineCap="round";
    this.context().lineWidth = 1;
    this.context().strokeStyle = "#ff0000";
    this.context().stroke();
    this.context().closePath();
  }
  
  this.resize = function(rect)
  {
    this.element.setAttribute('width',rect.width+"px");
    this.element.setAttribute('height',rect.height+"px");
  }
  
  this.show_guide = function(position,rect)
  {
    this.clear();
    this.context().beginPath();
    
    this.context().moveTo(0,0);
    this.context().lineTo(rect.width,0);
    this.context().lineTo(rect.width,rect.height);
    this.context().lineTo(0,rect.height);
    this.context().lineTo(0,0);
    
    this.context().lineCap="round";
    this.context().lineWidth = 1;
    this.context().strokeStyle = "#ff0000";
    this.context().stroke();
    this.context().closePath();
  }
  
  this.context = function()
  {
    return this.element.getContext('2d');
  }
  
  this.clear = function()
  {
    this.context().clearRect(0, 0, canvas.width, canvas.height);
  }
}