| Message ID | 20220617143549.35442-4-dse@thaumatec.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series |
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| Related | show |
Hi Daniel, Thank you for the patch. On Fri, Jun 17, 2022 at 04:35:49PM +0200, Daniel Semkowicz via libcamera-devel wrote: > Event loop was moved to be a part of CameraManager, so it is no longer > a user responsibility to control the event dispatching. > > Signed-off-by: Daniel Semkowicz <dse@thaumatec.com> > --- > .../guides/application-developer.rst | 38 ++++++++----------- > 1 file changed, 16 insertions(+), 22 deletions(-) > > diff --git a/Documentation/guides/application-developer.rst b/Documentation/guides/application-developer.rst > index a5f363cf..f4551f58 100644 > --- a/Documentation/guides/application-developer.rst > +++ b/Documentation/guides/application-developer.rst > @@ -27,10 +27,12 @@ defined names and types without the need of prefixing them. > #include <iomanip> > #include <iostream> > #include <memory> > + #include <thread> > > #include <libcamera/libcamera.h> > > using namespace libcamera; > + using namespace std::chrono_literals; > > int main() > { > @@ -506,35 +508,27 @@ and queue all the previously created requests. > for (std::unique_ptr<Request> &request : requests) > camera->queueRequest(request.get()); > > -Start an event loop > +Event processing > ~~~~~~~~~~~~~~~~~~~ You can shorten the underline. With this, Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> I can fix this when applying, there's no need to resubmit. > > -The libcamera library needs an event loop to monitor and dispatch events > -generated by the video devices part of the capture pipeline. libcamera provides > -its own ``EventDispatcher`` class (inspired by the `Qt event system`_) to > -process and deliver events generated by ``EventNotifiers``. > +libcamera creates an internal execution thread at `CameraManager::start()`_ > +time to decouple its own event processing from the application's main thread. > +Applications are thus free to manage their own execution opportunely, and only > +need to respond to events generated by libcamera emitted through signals. > > -.. _Qt event system: https://doc.qt.io/qt-5/eventsandfilters.html > +.. _CameraManager::start(): https://libcamera.org/api-html/classlibcamera_1_1CameraManager.html#a49e322880a2a26013bb0076788b298c5 > > -The libcamera library implements this by creating instances of the > -``EventNotifier`` class, which models a file descriptor event source registered > -to an ``EventDispatcher``. Whenever the ``EventDispatcher`` detects an event on > -a notifier it is monitoring, it emits the notifier's > -``EventNotifier::activated`` signal. The libcamera components connect to the > -notifiers' signals and emit application visible events, such as the > -``Camera::bufferReady`` and ``Camera::requestCompleted`` signals. > - > -The code below retrieves a reference to the system-wide event dispatcher and for > -the a fixed duration of 3 seconds, processes all the events detected in the > -system. > +Real-world applications will likely either integrate with the event loop of the > +framework they use, or create their own event loop to respond to user events. > +For the simple application presented in this example, it is enough to prevent > +immediate termination by pausing for 3 seconds. During that time, the libcamera > +thread will generate request completion events that the application will handle > +in the ``requestComplete()`` slot connected to the ``Camera::requestCompleted`` > +signal. > > .. code:: cpp > > - EventDispatcher *dispatcher = cm->eventDispatcher(); > - Timer timer; > - timer.start(3000); > - while (timer.isRunning()) > - dispatcher->processEvents(); > + std::this_thread::sleep_for(3000ms); > > Clean up and stop the application > ---------------------------------
diff --git a/Documentation/guides/application-developer.rst b/Documentation/guides/application-developer.rst index a5f363cf..f4551f58 100644 --- a/Documentation/guides/application-developer.rst +++ b/Documentation/guides/application-developer.rst @@ -27,10 +27,12 @@ defined names and types without the need of prefixing them. #include <iomanip> #include <iostream> #include <memory> + #include <thread> #include <libcamera/libcamera.h> using namespace libcamera; + using namespace std::chrono_literals; int main() { @@ -506,35 +508,27 @@ and queue all the previously created requests. for (std::unique_ptr<Request> &request : requests) camera->queueRequest(request.get()); -Start an event loop +Event processing ~~~~~~~~~~~~~~~~~~~ -The libcamera library needs an event loop to monitor and dispatch events -generated by the video devices part of the capture pipeline. libcamera provides -its own ``EventDispatcher`` class (inspired by the `Qt event system`_) to -process and deliver events generated by ``EventNotifiers``. +libcamera creates an internal execution thread at `CameraManager::start()`_ +time to decouple its own event processing from the application's main thread. +Applications are thus free to manage their own execution opportunely, and only +need to respond to events generated by libcamera emitted through signals. -.. _Qt event system: https://doc.qt.io/qt-5/eventsandfilters.html +.. _CameraManager::start(): https://libcamera.org/api-html/classlibcamera_1_1CameraManager.html#a49e322880a2a26013bb0076788b298c5 -The libcamera library implements this by creating instances of the -``EventNotifier`` class, which models a file descriptor event source registered -to an ``EventDispatcher``. Whenever the ``EventDispatcher`` detects an event on -a notifier it is monitoring, it emits the notifier's -``EventNotifier::activated`` signal. The libcamera components connect to the -notifiers' signals and emit application visible events, such as the -``Camera::bufferReady`` and ``Camera::requestCompleted`` signals. - -The code below retrieves a reference to the system-wide event dispatcher and for -the a fixed duration of 3 seconds, processes all the events detected in the -system. +Real-world applications will likely either integrate with the event loop of the +framework they use, or create their own event loop to respond to user events. +For the simple application presented in this example, it is enough to prevent +immediate termination by pausing for 3 seconds. During that time, the libcamera +thread will generate request completion events that the application will handle +in the ``requestComplete()`` slot connected to the ``Camera::requestCompleted`` +signal. .. code:: cpp - EventDispatcher *dispatcher = cm->eventDispatcher(); - Timer timer; - timer.start(3000); - while (timer.isRunning()) - dispatcher->processEvents(); + std::this_thread::sleep_for(3000ms); Clean up and stop the application ---------------------------------
Event loop was moved to be a part of CameraManager, so it is no longer a user responsibility to control the event dispatching. Signed-off-by: Daniel Semkowicz <dse@thaumatec.com> --- .../guides/application-developer.rst | 38 ++++++++----------- 1 file changed, 16 insertions(+), 22 deletions(-)