-- -----------------------------------------------------------------------
--
-- $Source: /repository/uni/htk/canvasitems/Arc.hs,v $
--
-- HTk - a GUI toolkit for Haskell  -  (c) Universitaet Bremen
--
-- $Revision: 1.5 $ from $Date: 2001/12/10 21:29:25 $  
-- Last modification by $Author: ludi $
--
-- -----------------------------------------------------------------------

---
-- HTk's <strong>arc</strong> canvas item.<br>
-- An arc object on a canvas widget.
module Arc (

  module CanvasItem,

  Arc,
  createArc,

  extent,
  getExtent,

  start,
  getStart

) where

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


-- -----------------------------------------------------------------------
-- arc
-- -----------------------------------------------------------------------

---
-- The <code>Arc</code> datatype.
data Arc = Arc GUIOBJECT deriving Eq


-- -----------------------------------------------------------------------
-- constructor
-- -----------------------------------------------------------------------

---
-- Constructs a new arc item.
-- @param cnv     - the parent canvas.
-- @param cnf     - the list of configuration options for this arc.
-- @return result - An arc item.
createArc :: Canvas -> [Config Arc] -> IO Arc
createArc cnv cnf =
  createCanvasItem cnv ARC Arc cnf [(-1,-1),(-1,-1)]


-- -----------------------------------------------------------------------
-- instantiations
-- -----------------------------------------------------------------------

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

---
-- An arc item can be destroyed.
instance Destroyable Arc where
---
-- Destroys an arc item.
  destroy = destroy . toGUIObject

---
-- You can synchronize on an arc item.
instance Synchronized Arc where
---
-- Synchronizes on an arc item.
  synchronize = synchronize . toGUIObject

---
-- An arc is a canvas item (any canvas item is an instance of the abstract
-- <code>class CanvasItem</code>).
instance CanvasItem Arc

---
-- An arc item can have several tags (handlers for a set of canvas items).
instance TaggedCanvasItem Arc

---
-- An arc is a filled canvas item (it has filling, outline, outline width,
-- and stipple configurations).
instance FilledCanvasItem Arc

---
-- An alternative way to specify arc's coords.
instance HasGeometry Arc where
---
-- Sets the arc's geometry (width, height, upper left position).
  geometry    = itemGeo
---
-- Gets the arcs geometry (width, height, upper left position).
  getGeometry = getGeo

---
-- You can specify the (upper left) position of an arc.
instance HasPosition Arc where
---
-- Sets the arc's (upper left) position.
  position    = itemPosition
---
-- Gets the (upper left) position of the arc.
  getPosition = getItemPosition

---
-- You can specify the size of an arc.
instance HasSize Arc where
---
-- Sets the width of an arc.
  width       = itemWidth
---
-- Gets the width of an arc.
  getWidth    = getItemWidth
---
-- Sets the height of an arc.
  height      = itemHeight
---
-- Gets the height of an arc.
  getHeight   = getItemHeight
---
-- Sets the size (width, height) of an arc.
  size        = itemSize
---
-- Gets the size (width, height) of an arc.
  getSize     = getItemSize


-- -----------------------------------------------------------------------
-- config options
-- -----------------------------------------------------------------------

type Degree = Double

---
-- Sets the length of an arc in counter-clockwise direction.
extent :: Degree -> Config Arc
extent d w = cset w "extent" d

---
-- Gets the length of an arc in counter-clockwise direction.
getExtent :: Arc -> IO Degree
getExtent w = cget w "extent"

---
-- Sets the starting angle of an arc.
start :: Degree -> Config Arc
start d w = cset w "start" d

---
-- Gets the starting angle of an arc.
getStart :: Arc -> IO Degree
getStart w = cget w "start"