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[PictureLoader] Fix worker thread shutdown and cross-thread cache clearing (#7292)

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* [PictureLoader] Fix worker thread shutdown and cross-thread cache clearing

clearNetworkCache() ran directly on the UI thread while the worker thread
owned the disk cache and redirect cache, racing cache reads/writes. Make it
a worker-thread slot invoked via a blocking queued call when the thread is
running, so the 'Cached card pictures have been reset.' message is truthful.

The worker thread was also never quit()/wait()ed: both destructors only
deleteLater'd their objects, so Qt warned 'QThread: Destroyed while thread
is still running' and leaked a running loop at exit. Wire the worker's
finished() signal to its own deleteLater() (canonical worker-object
pattern), add shutdownThread() to stop the loop, and let CardPictureLoader
destroy the QThread only after wait() has returned.

* [PictureLoader] Guard cache teardown and stop blocking the UI thread

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>
This commit is contained in:
BruebachL 2026-09-21 18:30:03 +02:00 • committed by GitHub
parent 14acf3bf64
commit 9f66a098ac
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7 changed files with 108 additions and 11 deletions
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27
cockatrice/src/interface/card_picture_loader/card_picture_loader.cpp
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@ -11,6 +11,7 @@
#include <QDir>
#include <QFileInfo>
#include <QMainWindow>
#include <QMetaObject>
#include <QMovie>
#include <QNetworkRequest>
#include <QPainter>
@ -43,6 +44,7 @@ CardPictureLoader::CardPictureLoader() : QObject(nullptr)
qRegisterMetaType<ExactCard>("ExactCard");
connect(worker, &CardPictureLoaderWorker::imageLoaded, this, &CardPictureLoader::imageLoaded);
connect(worker, &CardPictureLoaderWorker::networkCacheCleared, this, &CardPictureLoader::networkCacheCleared);
statusBar = new CardPictureLoaderStatusBar(nullptr);
QMainWindow *mainWindow = qobject_cast<QMainWindow *>(QApplication::activeWindow());
@ -58,7 +60,18 @@ CardPictureLoader::CardPictureLoader() : QObject(nullptr)
CardPictureLoader::~CardPictureLoader()
{
worker->deleteLater();
if (worker) {
// Capture the thread first: shutdownThread() blocks until the worker has been freed by the
// finished() -> deleteLater chain, after which the worker pointer must not be dereferenced.
QThread *pictureLoaderThread = worker->workerThread();
const bool stopped = worker->shutdownThread();
worker = nullptr;
// Deleting a QThread that is still running is undefined behaviour, so only free it once the
// bounded wait in shutdownThread() confirmed that it stopped.
if (stopped) {
delete pictureLoaderThread;
}
}
}
void CardPictureLoader::getCardBackPixmap(QPixmap &pixmap, QSize size)
@ -457,7 +470,17 @@ void CardPictureLoader::clearPixmapCache()
void CardPictureLoader::clearNetworkCache()
{
getInstance().worker->clearNetworkCache();
// During teardown the worker is released before this singleton, so a queued clear may still
// arrive with no worker left to run it.
CardPictureLoaderWorker *worker = getInstance().worker;
if (!worker) {
return;
}
// The disk cache and redirect cache are owned by the worker thread, so the clear has to run
// there. Invoke it asynchronously to keep the GUI responsive while the worker may be walking
// the user's picture directories or recursively deleting the cache directory; callers that
// need to know when it is done can listen for networkCacheCleared().
QMetaObject::invokeMethod(worker, &CardPictureLoaderWorker::clearNetworkCache, Qt::QueuedConnection);
}
void CardPictureLoader::cacheCardPixmaps(const QList<ExactCard> &cards)