{-# LANGUAGE CPP #-}
-- -*-haskell-*-
--  GIMP Toolkit (GTK) Widget OffscreenWindow
--
--  Author : Andy Stewart
--
--  Created: 25 Mar 2010
--
--  Copyright (C) 2010 Andy Stewart
--
--  This library is free software; you can redistribute it and/or
--  modify it under the terms of the GNU Lesser General Public
--  License as published by the Free Software Foundation; either
--  version 2.1 of the License, or (at your option) any later version.
--
--  This library is distributed in the hope that it will be useful,
--  but WITHOUT ANY WARRANTY; without even the implied warranty of
--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
--  Lesser General Public License for more details.
--
-- |
-- Maintainer  : gtk2hs-users@lists.sourceforge.net
-- Stability   : provisional
-- Portability : portable (depends on GHC)
--
-- A toplevel container widget used to manage offscreen rendering of child widgets.
--
-- * Module available since Gtk+ version 2.20
--
module Graphics.UI.Gtk.Windows.OffscreenWindow (
-- * Detail
-- | 'OffscreenWindow' is strictly intended to be used for obtaining snapshots of widgets that are not
-- part of a normal widget hierarchy. It differs from 'widgetGetSnapshot' in that the widget you
-- want to get a snapshot of need not be displayed on the user's screen as a part of a widget
-- hierarchy. However, since 'OffscreenWindow' is a toplevel widget you cannot obtain snapshots of a
-- full window with it since you cannot pack a toplevel widget in another toplevel.
--
-- The idea is to take a widget and manually set the state of it, add it to a 'OffscreenWindow' and
-- then retrieve the snapshot as a 'Pixmap' or 'Pixbuf'.
--
-- 'OffscreenWindow' derives from 'Window' only as an implementation detail. Applications should not
-- use any API specific to 'Window' to operate on this object. It should be treated as a 'Bin' that
-- has no parent widget.
--
-- When contained offscreen widgets are redrawn, 'OffscreenWindow' will emit a 'damageEvent' signal.

-- * Class Hierarchy
-- |
-- @
-- |  'GObject'
-- |   +----'Object'
-- |         +----'Widget'
-- |               +----'Container'
-- |                     +----'Bin'
-- |                           +----Window
-- |                                 +----'OffscreenWindow'
-- @

#if GTK_CHECK_VERSION(2,20,0)
-- * Types
  OffscreenWindow,
  OffscreenWindowClass,
  castToOffscreenWindow, gTypeOffscreenWindow,
  toOffscreenWindow,

-- * Constructors
  offscreenWindowNew,

-- * Methods
#if GTK_MAJOR_VERSION < 3
  offscreenWindowGetPixmap,
#endif
  offscreenWindowGetPixbuf,
#endif
) where

import Control.Monad	(liftM)

import System.Glib.FFI
import Graphics.UI.Gtk.Abstract.Object   (makeNewObject)
{#import Graphics.UI.Gtk.Types#}

{# context lib="gtk" prefix="gtk" #}

#if GTK_CHECK_VERSION(2,20,0)
-- | Creates a toplevel container widget that is used to retrieve snapshots of widgets without showing
-- them on the screen. For widgets that are on the screen and part of a normal widget hierarchy,
-- 'widgetGetSnapshot' can be used instead.
--
-- * Available since Gtk+ version 2.20
--
offscreenWindowNew :: IO OffscreenWindow
offscreenWindowNew =
  makeNewObject mkOffscreenWindow $
  liftM (castPtr :: Ptr Widget -> Ptr OffscreenWindow) $
  {#call gtk_offscreen_window_new #}

#if GTK_MAJOR_VERSION < 3
-- | Retrieves a snapshot of the contained widget in the form of a 'Pixmap'. If you need to keep this
-- around over window resizes then you should add a reference to it.
--
-- * Available since Gtk+ version 2.20
--
offscreenWindowGetPixmap :: OffscreenWindowClass self
                           => self -- ^ @offscreen@ the 'OffscreenWindow' contained widget.
                           -> IO (Maybe Pixmap) -- ^ returns   A 'Pixmap' pointer to the offscreen pixmap, or 'Nothing'.
offscreenWindowGetPixmap offscreen =
  maybeNull (makeNewGObject mkPixmap) $
  {#call gtk_offscreen_window_get_pixmap #}
     (toOffscreenWindow offscreen)
#endif

-- | Retrieves a snapshot of the contained widget in the form of a 'Pixbuf'.
--
-- * Available since Gtk+ version 2.20
--
offscreenWindowGetPixbuf :: OffscreenWindowClass self
                           => self -- ^ @offscreen@ the 'OffscreenWindow' contained widget.
                           -> IO (Maybe Pixbuf) -- ^ returns   A 'Pixbuf' pointer to the offscreen pixbuf, or 'Nothing'.
offscreenWindowGetPixbuf offscreen =
  maybeNull (wrapNewGObject mkPixbuf) $
  {#call gtk_offscreen_window_get_pixbuf #}
     (toOffscreenWindow offscreen)

#endif