-- -----------------------------------------------------------------------
--
-- $Source: /repository/uni/htk/canvasitems/Polygon.hs,v $
--
-- HTk - a GUI toolkit for Haskell  -  (c) Universitaet Bremen
--
-- $Revision: 1.4 $ from $Date: 2001/12/10 21:29:29 $  
-- Last modification by $Author: ludi $
--
-- -----------------------------------------------------------------------

---
-- HTk's <strong>polygon</strong> canvas item.<br>
-- A polygon object on a canvas widget.
module Polygon (

  module CanvasItem,

  Polygon,
  createPolygon

) where

import Core
import CanvasItem
import CanvasTag
import CanvasItemAux
import Synchronized
import Computation
import Destructible


-- -----------------------------------------------------------------------
-- Polygon
-- -----------------------------------------------------------------------

---
-- The <code>Polygon</code> datatype.
newtype Polygon = Polygon GUIOBJECT deriving Eq


-- -----------------------------------------------------------------------
-- Constructor
-- -----------------------------------------------------------------------

---
-- Constructs a new polygon item.
-- @param cnv     - the parent canvas.
-- @param cnf     - the list of configuration options for this polygon
--                  item.
-- @return result - A polygon item.
createPolygon :: Canvas -> [Config Polygon] -> IO Polygon
createPolygon cnv cnf =
  createCanvasItem cnv POLYGON Polygon cnf [(-1,-1),(-1,-1),(-1,-1)]


-- -----------------------------------------------------------------------
-- Instantiations
-- -----------------------------------------------------------------------

---
-- Internal.
instance GUIObject Polygon where 
---
-- Internal.
  toGUIObject (Polygon w) = w
---
-- Internal.
  cname _ = "Polygon"

---
-- An polygon item can be destroyed.
instance Destroyable Polygon where
---
-- Destroys a polygon item.
  destroy = destroy . toGUIObject

---
-- You can synchronize on a polygon item.
instance Synchronized Polygon where
---
-- Synchronizes on a polygon item.
  synchronize w = synchronize (toGUIObject w)

---
-- A polygon item is a canvas item (any canvas item is an instance of the
-- abstract <code>class CanvasItem</code>).
instance CanvasItem Polygon

---
-- A polygon item can have several tags (handlers for a set of canvas
-- items).
instance TaggedCanvasItem Polygon

---
-- A polygon item is a filled canvas item (it has filling, outline,
-- outline width, and stipple configurations).
instance FilledCanvasItem Polygon

---
-- A line is a segmented canvas item. It has a splinesteps and smooth
-- configuration.
instance SegmentedCanvasItem Polygon