For example, if an event or slot is triggered in a QObject (which ultimately triggers a function), which thread is calling that function? The answer lies in thread affinity. But let’s back up a bit. Qt threads and Event loops. Having the ability to asynchronously trigger functions, and raise/handle events means that Qt must have some kind of. The slot is executed in the thread that emitted the signal (which is not necessarily the thread where the receiver object lives).With queued connections, the slot is invoked when control returns to the event loop of the thread to which the object belongs. Cannot generate corresponding slot function when configure custom slot function in slot/signal editor. But it seems ok when configure with function inherited from a QtWidget. I found this issue on windows. Create a normal 'Qt Widget Application' Expand the Forms folder in the project explorer, double click mainwindow.ui. Signals, slots, QOBJECT, emit, SIGNAL, SLOT. Those are known as the Qt extension to C. They are in fact simple macros, defined in qobjectdefs.h. #define signals public #define slots /. nothing./ That is right, signals and slots are simple functions: the compiler will handle them them like any other functions. A call to inmain blocks the calling thread until the Qt event loop can process our message, execute the specified method and return the result. For situations where you don’t wait to wait for the result, or you wish to do some other processing while waiting for the result, QtUtils provides the inmainlater function. This works in the same way as inmain, but returns a reference to a Python.
Reentrancy and Thread-Safety ◦ Thread-Support in Qt Modules
QThread inherits QObject. It emits signals to indicate that the thread started or finished executing, and provides a few slots as well.
More interesting is that QObjects can be used in multiple threads, emit signals that invoke slots in other threads, and post events to objects that 'live' in other threads. This is possible because each thread is allowed to have its own event loop.
QObject Reentrancy
QObject is reentrant. Most of its non-GUI subclasses, such as QTimer, QTcpSocket, QUdpSocket and QProcess, are also reentrant, making it possible to use these classes from multiple threads simultaneously. Note that these classes are designed to be created and used from within a single thread; creating an object in one thread and calling its functions from another thread is not guaranteed to work. There are three constraints to be aware of:
- The child of a QObject must always be created in the thread where the parent was created. This implies, among other things, that you should never pass the QThread object (
this
) as the parent of an object created in the thread (since the QThread object itself was created in another thread). - Event driven objects may only be used in a single thread. Specifically, this applies to the timer mechanism and the network module. For example, you cannot start a timer or connect a socket in a thread that is not the object's thread.
- You must ensure that all objects created in a thread are deleted before you delete the QThread. This can be done easily by creating the objects on the stack in your run() implementation.
Although QObject is reentrant, the GUI classes, notably QWidget and all its subclasses, are not reentrant. They can only be used from the main thread. As noted earlier, QCoreApplication::exec() must also be called from that thread.
In practice, the impossibility of using GUI classes in other threads than the main thread can easily be worked around by putting time-consuming operations in a separate worker thread and displaying the results on screen in the main thread when the worker thread is finished. This is the approach used for implementing the Mandelbrot Example and the Blocking Fortune Client Example.
In general, creating QObjects before the QApplication is not supported and can lead to weird crashes on exit, depending on the platform. This means static instances of QObject are also not supported. A properly structured single or multi-threaded application should make the QApplication be the first created, and last destroyed QObject.
Per-Thread Event Loop
Each thread can have its own event loop. The initial thread starts its event loop using QCoreApplication::exec(), or for single-dialog GUI applications, sometimes QDialog::exec(). Other threads can start an event loop using QThread::exec(). Like QCoreApplication, QThread provides an exit(int) function and a quit() slot.
An event loop in a thread makes it possible for the thread to use certain non-GUI Qt classes that require the presence of an event loop (such as QTimer, QTcpSocket, and QProcess). It also makes it possible to connect signals from any threads to slots of a specific thread. This is explained in more detail in the Signals and Slots Across Threads section below.
A QObject instance is said to live in the thread in which it is created. Events to that object are dispatched by that thread's event loop. The thread in which a QObject lives is available using QObject::thread().
The QObject::moveToThread() function changes the thread affinity for an object and its children (the object cannot be moved if it has a parent).
Calling
delete
on a QObject from a thread other than the one that owns the object (or accessing the object in other ways) is unsafe, unless you guarantee that the object isn't processing events at that moment. Use QObject::deleteLater() instead, and a DeferredDelete event will be posted, which the event loop of the object's thread will eventually pick up. By default, the thread that owns a QObject is the thread that creates the QObject, but not after QObject::moveToThread() has been called.If no event loop is running, events won't be delivered to the object. For example, if you create a QTimer object in a thread but never call exec(), the QTimer will never emit its timeout() signal. Calling deleteLater() won't work either. (These restrictions apply to the main thread as well.)
You can manually post events to any object in any thread at any time using the thread-safe function QCoreApplication::postEvent(). The events will automatically be dispatched by the event loop of the thread where the object was created.
Event filters are supported in all threads, with the restriction that the monitoring object must live in the same thread as the monitored object. Similarly, QCoreApplication::sendEvent() (unlike postEvent()) can only be used to dispatch events to objects living in the thread from which the function is called.
Accessing QObject Subclasses from Other Threads
QObject and all of its subclasses are not thread-safe. This includes the entire event delivery system. It is important to keep in mind that the event loop may be delivering events to your QObject subclass while you are accessing the object from another thread.
If you are calling a function on an QObject subclass that doesn't live in the current thread and the object might receive events, you must protect all access to your QObject subclass's internal data with a mutex; otherwise, you may experience crashes or other undesired behavior.
Like other objects, QThread objects live in the thread where the object was created -- not in the thread that is created when QThread::run() is called. It is generally unsafe to provide slots in your QThread subclass, unless you protect the member variables with a mutex.
On the other hand, you can safely emit signals from your QThread::run() implementation, because signal emission is thread-safe.
Signals and Slots Across Threads
Qt supports these signal-slot connection types:
- Auto Connection (default) If the signal is emitted in the thread which the receiving object has affinity then the behavior is the same as the Direct Connection. Otherwise, the behavior is the same as the Queued Connection.'
- Direct Connection The slot is invoked immediately, when the signal is emitted. The slot is executed in the emitter's thread, which is not necessarily the receiver's thread.
- Queued Connection The slot is invoked when control returns to the event loop of the receiver's thread. The slot is executed in the receiver's thread.
- Blocking Queued Connection The slot is invoked as for the Queued Connection, except the current thread blocks until the slot returns.Note: Using this type to connect objects in the same thread will cause deadlock.
- Unique Connection The behavior is the same as the Auto Connection, but the connection is made only if it does not duplicate an existing connection. i.e., if the same signal is already connected to the same slot for the same pair of objects, then the connection is not made and connect() returns
false
.
The connection type can be specified by passing an additional argument to connect(). Be aware that using direct connections when the sender and receiver live in different threads is unsafe if an event loop is running in the receiver's thread, for the same reason that calling any function on an object living in another thread is unsafe.
QObject::connect() itself is thread-safe.
The Mandelbrot Example uses a queued connection to communicate between a worker thread and the main thread. To avoid freezing the main thread's event loop (and, as a consequence, the application's user interface), all the Mandelbrot fractal computation is done in a separate worker thread. The thread emits a signal when it is done rendering the fractal.
Similarly, the Blocking Fortune Client Example uses a separate thread for communicating with a TCP server asynchronously.
Reentrancy and Thread-Safety ◦ Thread-Support in Qt Modules
The QThread class provides a platform-independent way to manage threads. More...
Header: | #include <QThread> |
qmake: | QT += core |
Inherits: | QObject |
Public Types
enum | Priority { IdlePriority, LowestPriority, LowPriority, NormalPriority, HighPriority, …, InheritPriority } |
Public Functions
QThread(QObject *parent = nullptr) | |
virtual | ~QThread() |
QAbstractEventDispatcher * | eventDispatcher() const |
void | exit(int returnCode = 0) |
bool | isFinished() const |
bool | isInterruptionRequested() const |
bool | isRunning() const |
int | loopLevel() const |
QThread::Priority | priority() const |
void | requestInterruption() |
void | setEventDispatcher(QAbstractEventDispatcher *eventDispatcher) |
void | setPriority(QThread::Priority priority) |
void | setStackSize(uint stackSize) |
uint | stackSize() const |
bool | wait(QDeadlineTimer deadline = QDeadlineTimer(QDeadlineTimer::Forever)) |
bool | wait(unsigned long time) |
Reimplemented Public Functions
Public Slots
void | quit() |
void | start(QThread::Priority priority = InheritPriority) |
void | terminate() |
Signals
Static Public Members
QThread * | create(Function &&f, Args &&... args) |
QThread * | create(Function &&f) |
QThread * | currentThread() |
Qt::HANDLE | currentThreadId() |
int | idealThreadCount() |
void | msleep(unsigned long msecs) |
void | sleep(unsigned long secs) |
void | usleep(unsigned long usecs) |
void | yieldCurrentThread() |
Protected Functions
Static Protected Members
void | setTerminationEnabled(bool enabled = true) |
Detailed Description
A QThread object manages one thread of control within the program. QThreads begin executing in run(). By default, run() starts the event loop by calling exec() and runs a Qt event loop inside the thread.
You can use worker objects by moving them to the thread using QObject::moveToThread().
The code inside the Worker's slot would then execute in a separate thread. However, you are free to connect the Worker's slots to any signal, from any object, in any thread. It is safe to connect signals and slots across different threads, thanks to a mechanism called queued connections.
Another way to make code run in a separate thread, is to subclass QThread and reimplement run(). For example:
In that example, the thread will exit after the run function has returned. There will not be any event loop running in the thread unless you call exec().
It is important to remember that a QThread instance lives in the old thread that instantiated it, not in the new thread that calls run(). This means that all of QThread's queued slots and invoked methods will execute in the old thread. Thus, a developer who wishes to invoke slots in the new thread must use the worker-object approach; new slots should not be implemented directly into a subclassed QThread.
Unlike queued slots or invoked methods, methods called directly on the QThread object will execute in the thread that calls the method. When subclassing QThread, keep in mind that the constructor executes in the old thread while run() executes in the new thread. If a member variable is accessed from both functions, then the variable is accessed from two different threads. Check that it is safe to do so.
Note: Care must be taken when interacting with objects across different threads. As a general rule, functions can only be called from the thread that created the QThread object itself (e.g. setPriority()), unless the documentation says otherwise. See Synchronizing Threads for details.
Managing Threads
QThread will notifiy you via a signal when the thread is started() and finished(), or you can use isFinished() and isRunning() to query the state of the thread.
You can stop the thread by calling exit() or quit(). In extreme cases, you may want to forcibly terminate() an executing thread. However, doing so is dangerous and discouraged. Please read the documentation for terminate() and setTerminationEnabled() for detailed information.
From Qt 4.8 onwards, it is possible to deallocate objects that live in a thread that has just ended, by connecting the finished() signal to QObject::deleteLater().
Use wait() to block the calling thread, until the other thread has finished execution (or until a specified time has passed).
QThread also provides static, platform independent sleep functions: sleep(), msleep(), and usleep() allow full second, millisecond, and microsecond resolution respectively. These functions were made public in Qt 5.0.
Note: wait() and the sleep() functions should be unnecessary in general, since Qt is an event-driven framework. Instead of wait(), consider listening for the finished() signal. Instead of the sleep() functions, consider using QTimer.
The static functions currentThreadId() and currentThread() return identifiers for the currently executing thread. The former returns a platform specific ID for the thread; the latter returns a QThread pointer.
To choose the name that your thread will be given (as identified by the command
ps -L
on Linux, for example), you can call setObjectName() before starting the thread. If you don't call setObjectName(), the name given to your thread will be the class name of the runtime type of your thread object (for example, 'RenderThread'
in the case of the Mandelbrot Example, as that is the name of the QThread subclass). Note that this is currently not available with release builds on Windows.See also Thread Support in Qt, QThreadStorage, Synchronizing Threads, Mandelbrot Example, Semaphores Example, and Wait Conditions Example.
Member Type Documentation
enum QThread::Priority
This enum type indicates how the operating system should schedule newly created threads.
Constant | Value | Description |
---|---|---|
QThread::IdlePriority | 0 | scheduled only when no other threads are running. |
QThread::LowestPriority | 1 | scheduled less often than LowPriority. |
QThread::LowPriority | 2 | scheduled less often than NormalPriority. |
QThread::NormalPriority | 3 | the default priority of the operating system. |
QThread::HighPriority | 4 | scheduled more often than NormalPriority. |
QThread::HighestPriority | 5 | scheduled more often than HighPriority. |
QThread::TimeCriticalPriority | 6 | scheduled as often as possible. |
QThread::InheritPriority | 7 | use the same priority as the creating thread. This is the default. |
Member Function Documentation
QThread::QThread(QObject *parent = nullptr)
Constructs a new QThread to manage a new thread. The parent takes ownership of the QThread. The thread does not begin executing until start() is called.
See also start().
[signal]
void QThread::finished()
This signal is emitted from the associated thread right before it finishes executing.
When this signal is emitted, the event loop has already stopped running. No more events will be processed in the thread, except for deferred deletion events. This signal can be connected to QObject::deleteLater(), to free objects in that thread.
Note: If the associated thread was terminated using terminate(), it is undefined from which thread this signal is emitted.
Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
See also started().
[slot]
void QThread::quit()
Tells the thread's event loop to exit with return code 0 (success). Equivalent to calling QThread::exit(0).
This function does nothing if the thread does not have an event loop.
Note: This function is thread-safe.
See also exit() and QEventLoop.
[slot]
void QThread::start(QThread::Prioritypriority = InheritPriority)
Begins execution of the thread by calling run(). The operating system will schedule the thread according to the priority parameter. If the thread is already running, this function does nothing.
The effect of the priority parameter is dependent on the operating system's scheduling policy. In particular, the priority will be ignored on systems that do not support thread priorities (such as on Linux, see the sched_setscheduler documentation for more details).
See also run() and terminate().
[signal]
void QThread::started()
This signal is emitted from the associated thread when it starts executing, before the run() function is called.
Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.
See also finished().
[slot]
void QThread::terminate()
Terminates the execution of the thread. The thread may or may not be terminated immediately, depending on the operating system's scheduling policies. Use QThread::wait() after terminate(), to be sure.
When the thread is terminated, all threads waiting for the thread to finish will be woken up.
Warning: This function is dangerous and its use is discouraged. The thread can be terminated at any point in its code path. Threads can be terminated while modifying data. There is no chance for the thread to clean up after itself, unlock any held mutexes, etc. In short, use this function only if absolutely necessary.
Termination can be explicitly enabled or disabled by calling QThread::setTerminationEnabled(). Calling this function while termination is disabled results in the termination being deferred, until termination is re-enabled. See the documentation of QThread::setTerminationEnabled() for more information.
Note: This function is thread-safe.
See also setTerminationEnabled().
[virtual]
QThread::~QThread()
Destroys the QThread.
Note that deleting a QThread object will not stop the execution of the thread it manages. Deleting a running QThread (i.e. isFinished() returns
false
) will result in a program crash. Wait for the finished() signal before deleting the QThread.[static]
template <typename Function, typename Args> QThread *QThread::create(Function &&f, Args &&... args)
Creates a new QThread object that will execute the function f with the arguments args.
The new thread is not started -- it must be started by an explicit call to start(). This allows you to connect to its signals, move QObjects to the thread, choose the new thread's priority and so on. The function f will be called in the new thread.
Returns the newly created QThread instance.
Note: the caller acquires ownership of the returned QThread instance.
Note: this function is only available when using C++17.
Warning: do not call start() on the returned QThread instance more than once; doing so will result in undefined behavior.
This function was introduced in Qt 5.10.
See also start().
[static]
template <typename Function> QThread *QThread::create(Function &&f)
Creates a new QThread object that will execute the function f.
The new thread is not started -- it must be started by an explicit call to start(). This allows you to connect to its signals, move QObjects to the thread, choose the new thread's priority and so on. The function f will be called in the new thread.
Returns the newly created QThread instance.
Note: the caller acquires ownership of the returned QThread instance.
Warning: do not call start() on the returned QThread instance more than once; doing so will result in undefined behavior.
This function was introduced in Qt 5.10.
See also start().
[static]
QThread *QThread::currentThread()
Returns a pointer to a QThread which manages the currently executing thread.
[static]
Qt::HANDLE QThread::currentThreadId()
Returns the thread handle of the currently executing thread.
Warning: The handle returned by this function is used for internal purposes and should not be used in any application code.
Note: On Windows, this function returns the DWORD (Windows-Thread ID) returned by the Win32 function GetCurrentThreadId(), not the pseudo-HANDLE (Windows-Thread HANDLE) returned by the Win32 function GetCurrentThread().
[override virtual]
bool QThread::event(QEvent *event)
Reimplements: QObject::event(QEvent *e).
QAbstractEventDispatcher *QThread::eventDispatcher() const
Returns a pointer to the event dispatcher object for the thread. If no event dispatcher exists for the thread, this function returns
nullptr
.This function was introduced in Qt 5.0.
See also setEventDispatcher().
[protected]
int QThread::exec()
Enters the event loop and waits until exit() is called, returning the value that was passed to exit(). The value returned is 0 if exit() is called via quit().
This function is meant to be called from within run(). It is necessary to call this function to start event handling.
Note: This can only be called within the thread itself, i.e. when it is the current thread.
See also quit() and exit().
void QThread::exit(intreturnCode = 0)
Tells the thread's event loop to exit with a return code.
After calling this function, the thread leaves the event loop and returns from the call to QEventLoop::exec(). The QEventLoop::exec() function returns returnCode.
By convention, a returnCode of 0 means success, any non-zero value indicates an error.
Note that unlike the C library function of the same name, this function does return to the caller -- it is event processing that stops.
No QEventLoops will be started anymore in this thread until QThread::exec() has been called again. If the eventloop in QThread::exec() is not running then the next call to QThread::exec() will also return immediately.
Qt Slot Function Thread Chart
Note: This function is thread-safe.
See also quit() and QEventLoop.
[static]
int QThread::idealThreadCount()
Returns the ideal number of threads that can be run on the system. This is done querying the number of processor cores, both real and logical, in the system. This function returns 1 if the number of processor cores could not be detected.
bool QThread::isFinished() const
Returns
true
if the thread is finished; otherwise returns false
.Note: This function is thread-safe.
See also isRunning().
bool QThread::isInterruptionRequested() const
Qt Start Thread
Return true if the task running on this thread should be stopped. An interruption can be requested by requestInterruption().
This function can be used to make long running tasks cleanly interruptible. Never checking or acting on the value returned by this function is safe, however it is advisable do so regularly in long running functions. Take care not to call it too often, to keep the overhead low.
Note: This can only be called within the thread itself, i.e. when it is the current thread.
This function was introduced in Qt 5.2.
See also currentThread() and requestInterruption().
bool QThread::isRunning() const
Returns
true
if the thread is running; otherwise returns false
.Note: This function is thread-safe.
See also isFinished().
int QThread::loopLevel() const
Returns the current event loop level for the thread.
![Qt Slot Function Thread Qt Slot Function Thread](https://qiita-user-contents.imgix.net/https:%2F%2Fcdn.qiita.com%2Fassets%2Fpublic%2Fogp-background-1150d8b18a7c15795b701a55ae908f94.png?ixlib=rb-1.2.2&w=1200&mark=https:%2F%2Fqiita-user-contents.imgix.net%2F~text%3Fixlib%3Drb-1.2.2%26w%3D840%26h%3D380%26txt%3DQt%25E3%2581%25AEsignal%252Fslot%25E3%2581%25A8thread%25282%2529%26txt-color%3D%2523333%26txt-font%3DAvenir-Black%26txt-size%3D54%26txt-clip%3Dellipsis%26txt-align%3Dcenter%252Cmiddle%26s%3Dd893cbb3f6092ca5d14b6b36f47c6711&mark-align=center%2Cmiddle&blend=https:%2F%2Fqiita-user-contents.imgix.net%2F~text%3Fixlib%3Drb-1.2.2%26w%3D840%26h%3D500%26txt%3D%2540false-git%2540github%26txt-color%3D%2523333%26txt-font%3DAvenir-Black%26txt-size%3D45%26txt-align%3Dright%252Cbottom%26s%3Da4668b2401b66f6e8e1b7e07ab2274eb&blend-align=center%2Cmiddle&blend-mode=normal&s=885ca4ad442e916ba2a7b1c345f804f2)
Note: This can only be called within the thread itself, i.e. when it is the current thread.
This function was introduced in Qt 5.5.
[static]
void QThread::msleep(unsignedlongmsecs)
Forces the current thread to sleep for msecs milliseconds.
Avoid using this function if you need to wait for a given condition to change. Instead, connect a slot to the signal that indicates the change or use an event handler (see QObject::event()).
Note: This function does not guarantee accuracy. The application may sleep longer than msecs under heavy load conditions. Some OSes might round msecs up to 10 ms or 15 ms.
See also sleep() and usleep().
QThread::Priority QThread::priority() const
Returns the priority for a running thread. If the thread is not running, this function returns
InheritPriority
.This function was introduced in Qt 4.1.
See also Priority, setPriority(), and start().
Qt Signal And Slots
void QThread::requestInterruption()
Request the interruption of the thread. That request is advisory and it is up to code running on the thread to decide if and how it should act upon such request. This function does not stop any event loop running on the thread and does not terminate it in any way.
Note: This function is thread-safe.
This function was introduced in Qt 5.2.
See also isInterruptionRequested().
[virtual protected]
void QThread::run()
The starting point for the thread. After calling start(), the newly created thread calls this function. The default implementation simply calls exec().
You can reimplement this function to facilitate advanced thread management. Returning from this method will end the execution of the thread.
See also start() and wait().
void QThread::setEventDispatcher(QAbstractEventDispatcher *eventDispatcher)
Sets the event dispatcher for the thread to eventDispatcher. This is only possible as long as there is no event dispatcher installed for the thread yet. That is, before the thread has been started with start() or, in case of the main thread, before QCoreApplication has been instantiated. This method takes ownership of the object.
This function was introduced in Qt 5.0.
See also eventDispatcher().
void QThread::setPriority(QThread::Prioritypriority)
This function sets the priority for a running thread. If the thread is not running, this function does nothing and returns immediately. Use start() to start a thread with a specific priority.
The priority argument can be any value in the
QThread::Priority
enum except for InheritPriority
.The effect of the priority parameter is dependent on the operating system's scheduling policy. In particular, the priority will be ignored on systems that do not support thread priorities (such as on Linux, see http://linux.die.net/man/2/sched_setscheduler for more details).
This function was introduced in Qt 4.1.
See also Priority, priority(), and start().
void QThread::setStackSize(uintstackSize)
Sets the maximum stack size for the thread to stackSize. If stackSize is greater than zero, the maximum stack size is set to stackSize bytes, otherwise the maximum stack size is automatically determined by the operating system.
Warning: Most operating systems place minimum and maximum limits on thread stack sizes. The thread will fail to start if the stack size is outside these limits.
See also stackSize().
[static protected]
void QThread::setTerminationEnabled(boolenabled = true)
Enables or disables termination of the current thread based on the enabled parameter. The thread must have been started by QThread.
When enabled is false, termination is disabled. Future calls to QThread::terminate() will return immediately without effect. Instead, the termination is deferred until termination is enabled.
When enabled is true, termination is enabled. Future calls to QThread::terminate() will terminate the thread normally. If termination has been deferred (i.e. QThread::terminate() was called with termination disabled), this function will terminate the calling thread immediately. Note that this function will not return in this case.
See also terminate().
[static]
void QThread::sleep(unsignedlongsecs)
Forces the current thread to sleep for secs seconds.
Avoid using this function if you need to wait for a given condition to change. Instead, connect a slot to the signal that indicates the change or use an event handler (see QObject::event()).
Note: This function does not guarantee accuracy. The application may sleep longer than secs under heavy load conditions.
See also msleep() and usleep().
uint QThread::stackSize() const
Returns the maximum stack size for the thread (if set with setStackSize()); otherwise returns zero.
See also setStackSize().
[static]
void QThread::usleep(unsignedlongusecs)
Forces the current thread to sleep for usecs microseconds.
Avoid using this function if you need to wait for a given condition to change. Instead, connect a slot to the signal that indicates the change or use an event handler (see QObject::event()).
Note: This function does not guarantee accuracy. The application may sleep longer than usecs under heavy load conditions. Some OSes might round usecs up to 10 ms or 15 ms; on Windows, it will be rounded up to a multiple of 1 ms.
See also sleep() and msleep().
bool QThread::wait(QDeadlineTimerdeadline = QDeadlineTimer(QDeadlineTimer::Forever))
Blocks the thread until either of these conditions is met:
- The thread associated with this QThread object has finished execution (i.e. when it returns from run()). This function will return true if the thread has finished. It also returns true if the thread has not been started yet.
- The deadline is reached. This function will return false if the deadline is reached.
A deadline timer set to
QDeadlineTimer::Forever
(the default) will never time out: in this case, the function only returns when the thread returns from run() or if the thread has not yet started.This provides similar functionality to the POSIX
pthread_join()
function.This function was introduced in Qt 5.15.
See also sleep() and terminate().
bool QThread::wait(unsignedlongtime)
This is an overloaded function.
[static]
void QThread::yieldCurrentThread()
Yields execution of the current thread to another runnable thread, if any. Note that the operating system decides to which thread to switch.
© 2020 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.