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/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of Qt Creator.
**
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
****************************************************************************/
#include "guard.h"
#include "qtcassert.h"
/*! \class Utils::Guard
\brief The Guard class implements a recursive guard with locking mechanism.
It may be used as an alternative to QSignalBlocker.
QSignalBlocker blocks all signals of the object
which is usually not desirable. It may also block signals
which are needed internally by the object itself.
The Guard and GuardLocker classes don't block signals at all.
When calling a object's method which may in turn emit a signal
which you are connected to, and you want to ignore
this notification, you should keep the Guard object
as your class member and declare the GuardLocker object
just before calling the mentioned method, like:
\code
class MyClass : public QObject
{
\dots
private:
Guard updateGuard; // member of your class
};
\dots
void MyClass::updateOtherObject()
{
GuardLocker updatelocker(updateGuard);
otherObject->update(); // this may trigger a signal
}
\endcode
Inside a slot which is connected to the other's object signal
you may check if the guard is locked and ignore the further
operations in this case:
\code
void MyClass::otherObjectUpdated()
{
if (updateGuard.isLocked())
return;
// we didn't trigger the update
// so do update now
\dots
}
\endcode
The GuardLocker unlocks the Guard in its destructor.
The Guard object is recursive, you may declare many GuardLocker
objects for the same Guard instance and the Guard will be locked
as long as at least one GuardLocker object created for the Guard
is in scope.
*/
namespace Utils {
Guard::Guard() = default;
Guard::~Guard()
{
QTC_CHECK(m_lockCount == 0);
}
bool Guard::isLocked() const
{
return m_lockCount;
}
GuardLocker::GuardLocker(Guard &guard)
: m_guard(guard)
{
++m_guard.m_lockCount;
}
GuardLocker::~GuardLocker()
{
--m_guard.m_lockCount;
}
} // namespace Utils
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