Commit 0e39510c authored by Laurent Pinchart's avatar Laurent Pinchart
Browse files

libcamera: thread: Remove the unused setEventDispatcher() function

Custom event dispatchers for threads was an API meant to provide a way
to integrate libcamera in the application's event loop. This isn't used
anymore, as libcamera now creates internal threads. Drop the unused
Thread::setEventDispatcher() function, and update the documentation
Signed-off-by: default avatarLaurent Pinchart <>
Reviewed-by: default avatarKieran Bingham <>
parent 6b989658
......@@ -46,7 +46,6 @@ public:
static pid_t currentId();
EventDispatcher *eventDispatcher();
void setEventDispatcher(std::unique_ptr<EventDispatcher> dispatcher);
void dispatchMessages(Message::Type type = Message::Type::None);
......@@ -28,6 +28,13 @@
* interactions with application threads. Careful compliance with the threading
* model will ensure avoidance of race conditions.
* Every thread created by libcamera is associated with an instance of the
* Thread class. Those threads run an internal event loop by default to
* dispatch events to objects. Additionally, the main thread of the application
* (defined as the thread that calls CameraManager::start()) is also associated
* with a Thread instance, but has no event loop accessible to libcamera. Other
* application threads are not visible to libcamera.
* \section thread-objects Threads and Objects
* Instances of the Object class and all its derived classes are thread-aware
......@@ -39,13 +46,12 @@
* explicitly connected with ConnectionTypeDirect, will also be delivered from
* the object thread's event loop.
* All Object instances created by libcamera are bound to an internal thread,
* and applications don't need to provide an event loop to support them. Object
* instances created by applications require an event loop. It is the
* responsibility of applications to provide that event loop, either explicitly
* through CameraManager::setEventDispatcher(), or by running the default event
* loop provided by CameraManager::eventDispatcher() in their main thread. The
* main thread of an application is the one that calls CameraManager::start().
* All Object instances created internally by libcamera are bound to internal
* threads. As objects interact with thread event loops for proper operation,
* creating an Object instance in a thread that has no internal event loop (such
* as the main application thread, or libcamera threads that have a custom main
* loop), prevents some features of the Object class from being used. See
* Thread::exec() for more details.
* \section thread-signals Threads and Signals
......@@ -220,9 +226,9 @@ ThreadData *ThreadData::current()
* with the Object, Signal and EventDispatcher classes.
* Thread instances by default run an event loop until the exit() method is
* called. A custom event dispatcher may be installed with
* setEventDispatcher(), otherwise a poll-based event dispatcher is used. This
* behaviour can be overriden by overloading the run() method.
* called. The event loop dispatches events (messages, notifiers and timers)
* sent to the objects living in the thread. This behaviour can be modified by
* overriding the run() function.
* \context This class is \threadsafe.
......@@ -317,9 +323,17 @@ int Thread::exec()
* \brief Main method of the thread
* When the thread is started with start(), it calls this method in the context
* of the new thread. The run() method can be overloaded to perform custom
* work. When this method returns the thread execution is stopped, and the \ref
* finished signal is emitted.
* of the new thread. The run() method can be overridden to perform custom
* work, either custom initialization and cleanup before and after calling the
* Thread::exec() function, or a custom thread loop altogether. When this
* method returns the thread execution is stopped, and the \ref finished signal
* is emitted.
* Note that if this function is overridden and doesn't call Thread::exec(), no
* events will be dispatched to the objects living in the thread. These objects
* will not be able to use the EventNotifier, Timer or Message facilities. This
* includes functions that rely on message dispatching, such as
* Object::deleteLater().
* The base implementation just calls exec().
......@@ -435,38 +449,11 @@ pid_t Thread::currentId()
return data->tid_;
* \brief Set the event dispatcher
* \param[in] dispatcher Pointer to the event dispatcher
* Threads that run an event loop require an event dispatcher to integrate
* event notification and timers with the loop. Users that want to provide
* their own event dispatcher shall call this method once and only once before
* the thread is started with start(). If no event dispatcher is provided, a
* default poll-based implementation will be used.
* The Thread takes ownership of the event dispatcher and will delete it when
* the thread is destroyed.
void Thread::setEventDispatcher(std::unique_ptr<EventDispatcher> dispatcher)
if (data_->dispatcher_.load(std::memory_order_relaxed)) {
LOG(Thread, Warning) << "Event dispatcher is already set";
* \brief Retrieve the event dispatcher
* This method retrieves the event dispatcher set with setEventDispatcher().
* If no dispatcher has been set, a default poll-based implementation is created
* and returned, and no custom event dispatcher may be installed anymore.
* The returned event dispatcher is valid until the thread is destroyed.
* This function retrieves the internal event dispatcher for the thread. The
* returned event dispatcher is valid until the thread is destroyed.
* \return Pointer to the event dispatcher
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