{- |
Copyright  : Will Thompson, Iñaki García Etxebarria and Jonas Platte
License    : LGPL-2.1
Maintainer : Iñaki García Etxebarria (inaki@blueleaf.cc)

A structure containing a weak reference to a 'GI.GObject.Objects.Object.Object'.  It can either
be empty (i.e. point to 'Nothing'), or point to an object for as long as
at least one \"strong\" reference to that object exists. Before the
object\'s 'GI.GObject.Structs.ObjectClass.ObjectClass'.@/dispose/@ method is called, every 'GI.GObject.Structs.WeakRef.WeakRef'
associated with becomes empty (i.e. points to 'Nothing').

Like 'GI.GObject.Structs.Value.Value', 'GI.GObject.Structs.WeakRef.WeakRef' can be statically allocated, stack- or
heap-allocated, or embedded in larger structures.

Unlike @/g_object_weak_ref()/@ and @/g_object_add_weak_pointer()/@, this weak
reference is thread-safe: converting a weak pointer to a reference is
atomic with respect to invalidation of weak pointers to destroyed
objects.

If the object\'s 'GI.GObject.Structs.ObjectClass.ObjectClass'.@/dispose/@ method results in additional
references to the object being held, any @/GWeakRefs/@ taken
before it was disposed will continue to point to 'Nothing'.  If
@/GWeakRefs/@ are taken after the object is disposed and
re-referenced, they will continue to point to it until its refcount
goes back to zero, at which point they too will be invalidated.
-}

#define ENABLE_OVERLOADING (MIN_VERSION_haskell_gi_overloading(1,0,0) \
       && !defined(__HADDOCK_VERSION__))

module GI.GObject.Structs.WeakRef
    ( 

-- * Exported types
    WeakRef(..)                             ,
    noWeakRef                               ,


    ) where

import Data.GI.Base.ShortPrelude
import qualified Data.GI.Base.ShortPrelude as SP
import qualified Data.GI.Base.Overloading as O
import qualified Prelude as P

import qualified Data.GI.Base.Attributes as GI.Attributes
import qualified Data.GI.Base.ManagedPtr as B.ManagedPtr
import qualified Data.GI.Base.GClosure as B.GClosure
import qualified Data.GI.Base.GError as B.GError
import qualified Data.GI.Base.GVariant as B.GVariant
import qualified Data.GI.Base.GValue as B.GValue
import qualified Data.GI.Base.GParamSpec as B.GParamSpec
import qualified Data.GI.Base.CallStack as B.CallStack
import qualified Data.GI.Base.Properties as B.Properties
import qualified Data.Text as T
import qualified Data.ByteString.Char8 as B
import qualified Data.Map as Map
import qualified Foreign.Ptr as FP
import qualified GHC.OverloadedLabels as OL


-- | Memory-managed wrapper type.
newtype WeakRef = WeakRef (ManagedPtr WeakRef)
-- XXX Wrapping a foreign struct/union with no known destructor or size, leak?
instance WrappedPtr WeakRef where
    wrappedPtrCalloc = return nullPtr
    wrappedPtrCopy = return
    wrappedPtrFree = Nothing

-- | A convenience alias for `Nothing` :: `Maybe` `WeakRef`.
noWeakRef :: Maybe WeakRef
noWeakRef = Nothing


#if ENABLE_OVERLOADING
instance O.HasAttributeList WeakRef
type instance O.AttributeList WeakRef = WeakRefAttributeList
type WeakRefAttributeList = ('[ ] :: [(Symbol, *)])
#endif

#if ENABLE_OVERLOADING
type family ResolveWeakRefMethod (t :: Symbol) (o :: *) :: * where
    ResolveWeakRefMethod l o = O.MethodResolutionFailed l o

instance (info ~ ResolveWeakRefMethod t WeakRef, O.MethodInfo info WeakRef p) => OL.IsLabel t (WeakRef -> p) where
#if MIN_VERSION_base(4,10,0)
    fromLabel = O.overloadedMethod (O.MethodProxy :: O.MethodProxy info)
#else
    fromLabel _ = O.overloadedMethod (O.MethodProxy :: O.MethodProxy info)
#endif

#endif