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/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "nsISupports.idl"
%{C++
#include "mozilla/Attributes.h"
#include "mozilla/MemoryReporting.h"
// For MOZ_THREAD_SAFETY_OWNERSHIP_CHECKS_SUPPORTED.
#include "nsDebug.h"
#ifdef MOZ_THREAD_SAFETY_OWNERSHIP_CHECKS_SUPPORTED
#define MOZ_WEAKREF_DECL_OWNINGTHREAD nsAutoOwningThread _mWeakRefOwningThread;
#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD \
_mWeakRefOwningThread.AssertOwnership("nsWeakReference not thread-safe")
#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD_DELEGATED(that) \
(that)->_mWeakRefOwningThread.AssertOwnership("nsWeakReference not thread-safe")
#else
#define MOZ_WEAKREF_DECL_OWNINGTHREAD
#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD do { } while (false)
#define MOZ_WEAKREF_ASSERT_OWNINGTHREAD_DELEGATED(that) do { } while (false)
#endif
%}
/**
* An instance of |nsIWeakReference| is a proxy object that cooperates with
* its referent to give clients a non-owning, non-dangling reference. Clients
* own the proxy, and should generally manage it with an |nsCOMPtr| (see the
* type |nsWeakPtr| for a |typedef| name that stands out) as they would any
* other XPCOM object. The |QueryReferent| member function provides a
* (hopefully short-lived) owning reference on demand, through which clients
* can get useful access to the referent, while it still exists.
*
* @version 1.0
* @see nsISupportsWeakReference
* @see nsWeakReference
* @see nsWeakPtr
*/
[scriptable, uuid(9188bc85-f92e-11d2-81ef-0060083a0bcf)]
interface nsIWeakReference : nsISupports
{
/**
* |QueryReferent| queries the referent, if it exists, and like |QueryInterface|, produces
* an owning reference to the desired interface. It is designed to look and act exactly
* like (a proxied) |QueryInterface|. Don't hold on to the produced interface permanently;
* that would defeat the purpose of using a non-owning |nsIWeakReference| in the first place.
*/
[binaryname(QueryReferentFromScript)]
void QueryReferent( in nsIIDRef uuid, [iid_is(uuid), retval] out nsQIResult result );
%{C++
virtual size_t SizeOfOnlyThis(mozilla::MallocSizeOf aMallocSizeOf) const = 0;
/**
* Returns true if the referring object is alive. Otherwise, false.
*/
bool IsAlive() const
{
return !!mObject;
}
nsresult QueryReferent(const nsIID& aIID, void** aInstancePtr);
protected:
friend class nsSupportsWeakReference;
nsIWeakReference(nsISupports* aObject)
: mObject(aObject)
{
}
nsIWeakReference() = delete;
MOZ_WEAKREF_DECL_OWNINGTHREAD
// The object we're holding a weak reference to.
nsISupports* MOZ_NON_OWNING_REF mObject;
%}
};
/**
* |nsISupportsWeakReference| is a factory interface which produces appropriate
* instances of |nsIWeakReference|. Weak references in this scheme can only be
* produced for objects that implement this interface.
*
* @version 1.0
* @see nsIWeakReference
* @see nsSupportsWeakReference
*/
[scriptable, uuid(9188bc86-f92e-11d2-81ef-0060083a0bcf)]
interface nsISupportsWeakReference : nsISupports
{
/**
* |GetWeakReference| produces an appropriate instance of |nsIWeakReference|.
* As with all good XPCOM `getters', you own the resulting interface and should
* manage it with an |nsCOMPtr|.
*
* @see nsIWeakReference
* @see nsWeakPtr
* @see nsCOMPtr
*/
nsIWeakReference GetWeakReference();
};
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