[VisualDeckStorage] Use QFuture continuations instead of QFutureWatcher tracking

Co-authored-by: sentry[bot] <39604003+sentry[bot]@users.noreply.github.com>

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

@@ -10,7 +10,7 @@
 #include <QElapsedTimer>
 #include <QFile>
 #include <QFileInfo>
-#include <QFutureWatcher>
+#include <QFuture>
 #include <QMetaObject>
 #include <QMetaType>
 #include <QSet>
@@ -137,39 +137,6 @@ 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();
@@ -277,17 +244,15 @@ 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();
-
+    // The continuation is bound to this model as its context object: it runs on the UI thread,
+    // and Qt drops it if the model is destroyed first, so no result is delivered to a dead model.
+    QFuture<DeckScanResult> scan =
+        QtConcurrent::run([currentDeckPath]() -> DeckScanResult { return scanDeckDirectory(currentDeckPath); });
+    scan.then(this, [this, generation](const DeckScanResult &result) {
         if (generation != scanGeneration) {
             return; // A newer scan started while this one was running; drop the stale result.
         }
 
-        const DeckScanResult result = watcher->result();
         folderPaths = result.folderPaths;
 
         if (result.decks.isEmpty()) {
@@ -303,9 +268,6 @@ void VisualDeckStorageModel::startScan()
             beginLoad(row);
         }
     });
-
-    watcher->setFuture(
-        QtConcurrent::run([currentDeckPath]() -> DeckScanResult { return scanDeckDirectory(currentDeckPath); }));
 }
 
 void VisualDeckStorageModel::beginLoad(int row)
@@ -321,34 +283,7 @@ void VisualDeckStorageModel::beginLoad(int row)
     const DeckFileFormat::Format fmt = DeckFileFormat::getFormatFromName(filePath);
     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) {
-                    return; // The deck list was re-scanned while this load was running; drop the stale result.
-                }
-
-                // Queue the result and apply a bounded number per event loop turn so that
-                // finishing hundreds of loads at once cannot stall the UI thread.
-                const std::optional<DeckLoadResult> result = watcher->result();
-                PendingDeckLoad pending;
-                pending.filePath = filePath;
-                pending.generation = generation;
-                if (result) {
-                    pending.ok = true;
-                    pending.deck = std::move(result->deck);
-                    pending.lastModified = result->lastModified;
-                    pending.colorIdentity = std::move(result->colorIdentity);
-                }
-                pendingLoads.append(std::move(pending));
-                schedulePendingLoadDrain();
-            });
-
-    watcher->setFuture(QtConcurrent::run([filePath, fmt]() -> std::optional<DeckLoadResult> {
+    auto load = QtConcurrent::run([filePath, fmt]() -> std::optional<DeckLoadResult> {
         std::optional<LoadedDeck> deck = DeckLoader::loadFromFile(filePath, fmt, false);
         if (!deck) {
             return std::nullopt;
@@ -357,7 +292,28 @@ void VisualDeckStorageModel::beginLoad(int row)
         // keep the completion handler on the UI thread cheap.
         const QString colorIdentity = getDeckColorIdentity(deck->deckList, CardDatabaseManager::query());
         return DeckLoadResult{std::move(*deck), QFileInfo(filePath).lastModified(), colorIdentity};
-    }));
+    });
+
+    // Bound to this model as context: runs on the UI thread and is dropped if the model is destroyed first.
+    load.then(this, [this, filePath, generation](std::optional<DeckLoadResult> result) {
+        if (generation != scanGeneration) {
+            return; // The deck list was re-scanned while this load was running; drop the stale result.
+        }
+
+        // Queue the result and apply a bounded number per event loop turn so that
+        // finishing hundreds of loads at once cannot stall the UI thread.
+        PendingDeckLoad pending;
+        pending.filePath = filePath;
+        pending.generation = generation;
+        if (result) {
+            pending.ok = true;
+            pending.deck = std::move(result->deck);
+            pending.lastModified = result->lastModified;
+            pending.colorIdentity = std::move(result->colorIdentity);
+        }
+        pendingLoads.append(std::move(pending));
+        schedulePendingLoadDrain();
+    });
 }
 
 void VisualDeckStorageModel::schedulePendingLoadDrain()

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

@@ -17,11 +17,9 @@
 
 #include <QAbstractListModel>
 #include <QDateTime>
-#include <QFutureWatcherBase>
 #include <QHash>
 #include <QList>
 #include <QModelIndex>
-#include <QPointer>
 #include <QString>
 #include <QStringList>
 #include <QVector>
@@ -109,12 +107,6 @@ 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;
@@ -185,8 +177,6 @@ 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();
@@ -201,9 +191,6 @@ 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.
-
-    /// Scan/load watchers whose future has not finished yet.
-    QList<QPointer<QFutureWatcherBase>> activeWatchers;
 };
 
 #endif // VISUAL_DECK_STORAGE_MODEL_H

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

@@ -157,36 +157,6 @@ 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

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