{-# LANGUAGE MultiParamTypeClasses #-}

module Phi.Widgets.AlphaBox ( alphaBox
                            ) where

import Phi.Types
import Phi.Widget

import Control.Monad

import Graphics.Rendering.Cairo


data AlphaBoxState = AlphaBoxState ![WidgetState] deriving Eq

data AlphaBox = AlphaBox !Double ![Widget] deriving (Show, Eq)


instance WidgetClass AlphaBox AlphaBoxState where
  initWidget (AlphaBox _ widgets) phi disp = liftM AlphaBoxState $ mapM (createWidgetState phi disp) widgets
  
  minSize (AlphaBox _ _) (AlphaBoxState widgetStates) height screen =
    sum (map (\(WidgetState {stateWidget = w, statePrivateData = priv}) -> minSize w priv height screen) widgetStates)
  
  weight (AlphaBox _ widgets) = sum (map (\(Widget w) -> weight w) widgets)
  
  layout (AlphaBox _ _) (AlphaBoxState widgetStates) width height screen = AlphaBoxState $ layoutWidgets widgetStates 0 0 width height screen

  render (AlphaBox alpha _) (AlphaBoxState widgetStates) x y w h screen = do
    renderWithSimilarSurface ContentColorAlpha w h $ \surface -> do
      renderWith surface $ do
        renderWidgets widgetStates screen x y
        
        setOperator OperatorDestIn
        setSourceRGBA 0 0 0 alpha
        paint
      
      withPatternForSurface surface setSource
      paint
        
        
    
  handleMessage _ (AlphaBoxState widgetStates) m = AlphaBoxState $ handleMessageWidgets m widgetStates


alphaBox :: Double -> [Widget] -> Widget
alphaBox alpha = Widget . AlphaBox alpha