[VisualDeckStorage] Cancel in-flight deck loads and enforce teardown order on destruction

cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_model.cpp

@@ -137,6 +137,39 @@ VisualDeckStorageModel::VisualDeckStorageModel(QObject *parent) : QAbstractListM
 {
 }
 
+VisualDeckStorageModel::~VisualDeckStorageModel()
+{
+    // Invalidate every outstanding result and drop queued work.
+    ++scanGeneration;
+    pendingLoads.clear();
+    drainScheduled = false;
+
+    // Detach and destroy the watchers of still-running futures explicitly, before
+    // QObject teardown, so none of their finished() lambdas (which capture this)
+    // can fire into a half-destroyed model. Futures that have not started yet are
+    // cancelled; ones already running finish on the pool and their result is dropped.
+    const QList<QPointer<QFutureWatcherBase>> watchers = std::exchange(activeWatchers, {});
+    for (const QPointer<QFutureWatcherBase> &watcher : watchers) {
+        if (!watcher) {
+            continue;
+        }
+        disconnect(watcher, nullptr, this, nullptr);
+        watcher->cancel();
+        delete watcher.data();
+    }
+}
+
+void VisualDeckStorageModel::trackWatcher(QFutureWatcherBase *watcher)
+{
+    activeWatchers.append(QPointer<QFutureWatcherBase>(watcher));
+}
+
+void VisualDeckStorageModel::forgetWatcher(QFutureWatcherBase *watcher)
+{
+    activeWatchers.removeIf(
+        [watcher](const QPointer<QFutureWatcherBase> &tracked) { return !tracked || tracked.data() == watcher; });
+}
+
 int VisualDeckStorageModel::rowCount(const QModelIndex &parent) const
 {
     return parent.isValid() ? 0 : decks.size();
@@ -245,7 +278,9 @@ void VisualDeckStorageModel::startScan()
     // The scan (directory walk + one stat per file) runs on a worker thread so that
     // constructing the widget never stalls the UI thread on a large deck folder.
     auto *watcher = new QFutureWatcher<DeckScanResult>(this);
+    trackWatcher(watcher);
     connect(watcher, &QFutureWatcher<DeckScanResult>::finished, this, [this, watcher, generation] {
+        forgetWatcher(watcher);
         watcher->deleteLater();
 
         if (generation != scanGeneration) {
@@ -287,8 +322,10 @@ void VisualDeckStorageModel::beginLoad(int row)
     const int generation = scanGeneration;
 
     auto *watcher = new QFutureWatcher<std::optional<DeckLoadResult>>(this);
+    trackWatcher(watcher);
     connect(watcher, &QFutureWatcher<std::optional<DeckLoadResult>>::finished, this,
             [this, watcher, filePath, generation] {
+                forgetWatcher(watcher);
                 watcher->deleteLater();
 
                 if (generation != scanGeneration) {

cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_model.h

@@ -17,9 +17,11 @@
 
 #include <QAbstractListModel>
 #include <QDateTime>
+#include <QFutureWatcherBase>
 #include <QHash>
 #include <QList>
 #include <QModelIndex>
+#include <QPointer>
 #include <QString>
 #include <QStringList>
 #include <QVector>
@@ -107,6 +109,12 @@ class VisualDeckStorageModel : public QAbstractListModel
 public:
     explicit VisualDeckStorageModel(QObject *parent = nullptr);
 
+    /**
+     * @brief Cancels and detaches every background scan/load still in flight, so no
+     * QFutureWatcher can deliver a result into (or outlive) a destroyed model.
+     */
+    ~VisualDeckStorageModel() override;
+
     /// @name Qt model overrides
     ///@{
     [[nodiscard]] int rowCount(const QModelIndex &parent = QModelIndex()) const override;
@@ -177,6 +185,8 @@ private:
     static void recomputeDeckMetadata(DeckPreviewData &data, bool recomputeColorIdentity = true);
     void reindexFilePaths();
     void schedulePendingLoadDrain();
+    void trackWatcher(QFutureWatcherBase *watcher);
+    void forgetWatcher(QFutureWatcherBase *watcher);
 
 private slots:
     void drainPendingLoads();
@@ -191,6 +201,7 @@ private:
     int scanGeneration = 0;                ///< Bumped on every scan so stale results are ignored.
     QVector<PendingDeckLoad> pendingLoads; ///< Finished background loads waiting to be applied.
     bool drainScheduled = false;           ///< Whether a queued drain pass is already pending.
+    QList<QPointer<QFutureWatcherBase>> activeWatchers; ///< Scan/load watchers whose future has not finished yet.
 };
 
 #endif // VISUAL_DECK_STORAGE_MODEL_H

cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_widget.cpp

@@ -157,6 +157,36 @@ VisualDeckStorageWidget::VisualDeckStorageWidget(QWidget *parent) : QWidget(pare
     }
 }
 
+VisualDeckStorageWidget::~VisualDeckStorageWidget()
+{
+    // Tear down in dependency order instead of relying on QObject child creation order,
+    // which would destroy the model first while the proxy and the deck preview widgets
+    // (which hold raw VisualDeckStorageModel pointers) are still alive.
+    if (refreshTimer) {
+        refreshTimer->stop();
+    }
+
+    // 1. Views: folder and deck preview widgets live inside the scroll area.
+    delete scrollArea;
+    scrollArea = nullptr;
+    folderWidget = nullptr;
+
+    // 2. Proxy: detach it from the model before either is destroyed.
+    if (storageProxyModel) {
+        disconnect(storageProxyModel, nullptr, this, nullptr);
+        storageProxyModel->setSourceModel(nullptr);
+        delete storageProxyModel;
+        storageProxyModel = nullptr;
+    }
+
+    // 3. Model last; its destructor cancels and detaches in-flight background loads.
+    if (storageModel) {
+        disconnect(storageModel, nullptr, this, nullptr);
+        delete storageModel;
+        storageModel = nullptr;
+    }
+}
+
 void VisualDeckStorageWidget::refreshIfPossible()
 {
     if (scrollArea->widget() != databaseLoadIndicator) {

cockatrice/src/interface/widgets/visual_deck_storage/visual_deck_storage_widget.h

@@ -34,6 +34,7 @@ class VisualDeckStorageWidget final : public QWidget
     Q_OBJECT
 public:
     explicit VisualDeckStorageWidget(QWidget *parent);
+    ~VisualDeckStorageWidget() override;
     void refreshIfPossible();
     void retranslateUi();
     void setShareSelectable(bool selectable);