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{ "id": 16268, "url": "https://patchwork.libcamera.org/api/1.1/patches/16268/?format=api", "web_url": "https://patchwork.libcamera.org/patch/16268/", "project": { "id": 1, "url": "https://patchwork.libcamera.org/api/1.1/projects/1/?format=api", "name": "libcamera", "link_name": "libcamera", "list_id": "libcamera_core", "list_email": "libcamera-devel@lists.libcamera.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<20220617143549.35442-4-dse@thaumatec.com>", "date": "2022-06-17T14:35:49", "name": "[libcamera-devel,v2,3/3] Documentation: Update the \"Start an event loop\" section", "commit_ref": null, "pull_url": null, "state": "accepted", "archived": false, "hash": "3d3db76877758bbc256b3d5f46f77394ab61cdb9", "submitter": { "id": 126, "url": "https://patchwork.libcamera.org/api/1.1/people/126/?format=api", "name": "Daniel Semkowicz", "email": "dse@thaumatec.com" }, "delegate": null, "mbox": "https://patchwork.libcamera.org/patch/16268/mbox/", "series": [ { "id": 3189, "url": "https://patchwork.libcamera.org/api/1.1/series/3189/?format=api", "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=3189", "date": "2022-06-17T14:35:46", "name": "Documentation: Update code examples in Application Writer's Guide", "version": 2, "mbox": "https://patchwork.libcamera.org/series/3189/mbox/" } ], "comments": "https://patchwork.libcamera.org/api/patches/16268/comments/", "check": "pending", "checks": "https://patchwork.libcamera.org/api/patches/16268/checks/", "tags": {}, "headers": { "Return-Path": "<libcamera-devel-bounces@lists.libcamera.org>", "X-Original-To": "parsemail@patchwork.libcamera.org", "Delivered-To": "parsemail@patchwork.libcamera.org", "Received": [ "from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id EAB26C3275\n\tfor <parsemail@patchwork.libcamera.org>;\n\tFri, 17 Jun 2022 14:36:05 +0000 (UTC)", "from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 5660B65632;\n\tFri, 17 Jun 2022 16:36:05 +0200 (CEST)", "from mail-ej1-x62e.google.com (mail-ej1-x62e.google.com\n\t[IPv6:2a00:1450:4864:20::62e])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 5B97D65634\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tFri, 17 Jun 2022 16:36:04 +0200 (CEST)", "by mail-ej1-x62e.google.com with SMTP id hj18so8551716ejb.0\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tFri, 17 Jun 2022 07:36:04 -0700 (PDT)", "from localhost.localdomain (ip092042140082.rev.nessus.at.\n\t[92.42.140.82]) by smtp.gmail.com with ESMTPSA id\n\tu20-20020aa7d554000000b0042a2d9af0f8sm3746189edr.79.2022.06.17.07.36.02\n\t(version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256);\n\tFri, 17 Jun 2022 07:36:03 -0700 (PDT)" ], "DKIM-Signature": [ "v=1; 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\n\tFri, 17 Jun 2022 07:36:03 -0700 (PDT)", "To": "libcamera-devel@lists.libcamera.org", "Date": "Fri, 17 Jun 2022 16:35:49 +0200", "Message-Id": "<20220617143549.35442-4-dse@thaumatec.com>", "X-Mailer": "git-send-email 2.34.1", "In-Reply-To": "<20220617143549.35442-1-dse@thaumatec.com>", "References": "<20220617143549.35442-1-dse@thaumatec.com>", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "Subject": "[libcamera-devel] [PATCH v2 3/3] Documentation: Update the \"Start\n\tan event loop\" section", "X-BeenThere": "libcamera-devel@lists.libcamera.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "<libcamera-devel.lists.libcamera.org>", "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>", "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>", "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>", "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>", "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>", "From": "Daniel Semkowicz via libcamera-devel\n\t<libcamera-devel@lists.libcamera.org>", "Reply-To": "Daniel Semkowicz <dse@thaumatec.com>", "Errors-To": "libcamera-devel-bounces@lists.libcamera.org", "Sender": "\"libcamera-devel\" <libcamera-devel-bounces@lists.libcamera.org>" }, "content": "Event loop was moved to be a part of CameraManager, so it is no longer\na user responsibility to control the event dispatching.\n\nSigned-off-by: Daniel Semkowicz <dse@thaumatec.com>\n---\n .../guides/application-developer.rst | 38 ++++++++-----------\n 1 file changed, 16 insertions(+), 22 deletions(-)", "diff": "diff --git a/Documentation/guides/application-developer.rst b/Documentation/guides/application-developer.rst\nindex a5f363cf..f4551f58 100644\n--- a/Documentation/guides/application-developer.rst\n+++ b/Documentation/guides/application-developer.rst\n@@ -27,10 +27,12 @@ defined names and types without the need of prefixing them.\n #include <iomanip>\n #include <iostream>\n #include <memory>\n+ #include <thread>\n \n #include <libcamera/libcamera.h>\n \n using namespace libcamera;\n+ using namespace std::chrono_literals;\n \n int main()\n {\n@@ -506,35 +508,27 @@ and queue all the previously created requests.\n for (std::unique_ptr<Request> &request : requests)\n camera->queueRequest(request.get());\n \n-Start an event loop\n+Event processing\n ~~~~~~~~~~~~~~~~~~~\n \n-The libcamera library needs an event loop to monitor and dispatch events\n-generated by the video devices part of the capture pipeline. libcamera provides\n-its own ``EventDispatcher`` class (inspired by the `Qt event system`_) to\n-process and deliver events generated by ``EventNotifiers``.\n+libcamera creates an internal execution thread at `CameraManager::start()`_\n+time to decouple its own event processing from the application's main thread.\n+Applications are thus free to manage their own execution opportunely, and only\n+need to respond to events generated by libcamera emitted through signals.\n \n-.. _Qt event system: https://doc.qt.io/qt-5/eventsandfilters.html\n+.. _CameraManager::start(): https://libcamera.org/api-html/classlibcamera_1_1CameraManager.html#a49e322880a2a26013bb0076788b298c5\n \n-The libcamera library implements this by creating instances of the\n-``EventNotifier`` class, which models a file descriptor event source registered\n-to an ``EventDispatcher``. Whenever the ``EventDispatcher`` detects an event on\n-a notifier it is monitoring, it emits the notifier's\n-``EventNotifier::activated`` signal. The libcamera components connect to the\n-notifiers' signals and emit application visible events, such as the\n-``Camera::bufferReady`` and ``Camera::requestCompleted`` signals.\n-\n-The code below retrieves a reference to the system-wide event dispatcher and for\n-the a fixed duration of 3 seconds, processes all the events detected in the\n-system.\n+Real-world applications will likely either integrate with the event loop of the\n+framework they use, or create their own event loop to respond to user events.\n+For the simple application presented in this example, it is enough to prevent\n+immediate termination by pausing for 3 seconds. During that time, the libcamera\n+thread will generate request completion events that the application will handle\n+in the ``requestComplete()`` slot connected to the ``Camera::requestCompleted``\n+signal.\n \n .. code:: cpp\n \n- EventDispatcher *dispatcher = cm->eventDispatcher();\n- Timer timer;\n- timer.start(3000);\n- while (timer.isRunning())\n- dispatcher->processEvents();\n+ std::this_thread::sleep_for(3000ms);\n \n Clean up and stop the application\n ---------------------------------\n", "prefixes": [ "libcamera-devel", "v2", "3/3" ] }