Revision control
++ // Copyright (C) 2025 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
++
++ #include "queueworker.h"
++
++ /* view needs 8 items and cacheBuffer of 2 items above and below to show visible area, so limit queue max length to that. */
++ static constexpr int s_queueMaxLength{12};
++
++ QueueWorker::QueueWorker()
++ : QObject{nullptr}
++ {
++ connect(this,
++ &QueueWorker::triggerQueueProcessing,
++ this,
++ &QueueWorker::processQueue,
++ Qt::QueuedConnection);
++ }
++
++ void QueueWorker::abort()
++ {
++ m_killSignalReceived = true;
++ }
++
++ void QueueWorker::fetchData(int id)
++ {
++ if (m_indicesAlreadyFetched.contains(id) || m_indicesToFetch.contains(id)
++ || m_killSignalReceived)
++ return;
++
++ /* This is signal from UI thread. It is likely that there are more than one in queue.
++ * Add our own triggerQueueProcessing() signal to the end of event queue and add id to queue of IDs.
++ * Then let all queued signals to be processed until QueueWorker receives its own signal.
++ */
++ sendTriggerQueueProcessingSignal(id);
++ }
++
++ void QueueWorker::processQueue()
++ {
++ /* This slot receives QueueWorker's own signal after all signals from UI thread have been processed. */
++ m_queueProcessingSignalSent = false;
++ const auto index = m_indicesToFetch.dequeue();
++ emit processing(index);
++ const auto data = m_remoteMedia.getElements(1, index);
++ m_indicesAlreadyFetched.insert(index);
++ emit dataFetched(index, data.front());
++ if (!m_indicesToFetch.empty() && !m_killSignalReceived) {
++ /* Queueworker should process more indices, but the UI thread may have sent more signals during previous processing.
++ * Add our own signal to end of event queue and let all preceding signals to be processed before continuing.
++ */
++ emit triggerQueueProcessing(QPrivateSignal{});
++ m_queueProcessingSignalSent = true;
++ }
++ /* Else all fetches have been processed so far. */
++ }
++
++ void QueueWorker::sendTriggerQueueProcessingSignal(int id)
++ {
++ /* Make sure excess IDs are removed. */
++ while (m_indicesToFetch.size() >= s_queueMaxLength) {
++ emit dropped(m_indicesToFetch.dequeue());
++ }
++ /* Before calling this function QueueWorker has ensured that m_indicesToFetch doesn't contain id yet, so just add id. */
++ m_indicesToFetch.enqueue(id);
++ if (!m_queueProcessingSignalSent) {
++ emit triggerQueueProcessing(QPrivateSignal{});
++ m_queueProcessingSignalSent = true;
++ }
++ }