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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#include "guard.h"
#include "qtcassert.h"
/*!
\class Utils::Guard
\inmodule QtCreator
\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;
}
void Guard::lock()
{
++m_lockCount;
}
void Guard::unlock()
{
QTC_CHECK(m_lockCount > 0);
--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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