Correctly limit overview transaction list

The way that the main overview page limits the number
of transactions displayed (currently 5) is not
an appropriate use of Qt. If it's run with a DEBUG
build of Qt, it'll result in a segfault in certain
relatively common situations. Instead of artificially
limiting the rowCount() in the subclassed proxy
filter, we hide/unhide the rows in the displaying
QListView upon any changes in the sorted proxy filter.

src/qt/overviewpage.cpp

@@ -262,7 +262,6 @@ void OverviewPage::setWalletModel(WalletModel *model)
         // Set up transaction list
         filter.reset(new TransactionFilterProxy());
         filter->setSourceModel(model->getTransactionTableModel());
-        filter->setLimit(NUM_ITEMS);
         filter->setDynamicSortFilter(true);
         filter->setSortRole(Qt::EditRole);
         filter->setShowInactive(false);
@@ -271,6 +270,10 @@ void OverviewPage::setWalletModel(WalletModel *model)
         ui->listTransactions->setModel(filter.get());
         ui->listTransactions->setModelColumn(TransactionTableModel::ToAddress);
 
+        connect(filter.get(), &TransactionFilterProxy::rowsInserted, this, &OverviewPage::LimitTransactionRows);
+        connect(filter.get(), &TransactionFilterProxy::rowsRemoved, this, &OverviewPage::LimitTransactionRows);
+        connect(filter.get(), &TransactionFilterProxy::rowsMoved, this, &OverviewPage::LimitTransactionRows);
+        LimitTransactionRows();
         // Keep up to date with wallet
         setBalance(model->getCachedBalance());
         connect(model, &WalletModel::balanceChanged, this, &OverviewPage::setBalance);
@@ -299,6 +302,16 @@ void OverviewPage::changeEvent(QEvent* e)
     QWidget::changeEvent(e);
 }
 
+// Only show most recent NUM_ITEMS rows
+void OverviewPage::LimitTransactionRows()
+{
+    if (filter && ui->listTransactions && ui->listTransactions->model() && filter.get() == ui->listTransactions->model()) {
+        for (int i = 0; i < filter->rowCount(); ++i) {
+            ui->listTransactions->setRowHidden(i, i >= NUM_ITEMS);
+        }
+    }
+}
+
 void OverviewPage::updateDisplayUnit()
 {
     if (walletModel && walletModel->getOptionsModel()) {

src/qt/overviewpage.h

@@ -60,6 +60,7 @@ public Q_SLOTS:
     std::unique_ptr<TransactionFilterProxy> filter;
 
 private Q_SLOTS:
+    void LimitTransactionRows();
     void updateDisplayUnit();
     void handleTransactionClicked(const QModelIndex &index);
     void updateAlerts(const QString &warnings);

src/qt/transactionfilterproxy.cpp

@@ -88,25 +88,8 @@ void TransactionFilterProxy::setWatchOnlyFilter(WatchOnlyFilter filter)
     invalidateFilter();
 }
 
-void TransactionFilterProxy::setLimit(int limit)
-{
-    this->limitRows = limit;
-}
-
 void TransactionFilterProxy::setShowInactive(bool _showInactive)
 {
     this->showInactive = _showInactive;
     invalidateFilter();
 }
-
-int TransactionFilterProxy::rowCount(const QModelIndex &parent) const
-{
-    if(limitRows != -1)
-    {
-        return std::min(QSortFilterProxyModel::rowCount(parent), limitRows);
-    }
-    else
-    {
-        return QSortFilterProxyModel::rowCount(parent);
-    }
-}

src/qt/transactionfilterproxy.h

@@ -42,14 +42,9 @@ class TransactionFilterProxy : public QSortFilterProxyModel
     void setMinAmount(const CAmount& minimum);
     void setWatchOnlyFilter(WatchOnlyFilter filter);
 
-    /** Set maximum number of rows returned, -1 if unlimited. */
-    void setLimit(int limit);
-
     /** Set whether to show conflicted transactions. */
     void setShowInactive(bool showInactive);
 
-    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
-
 protected:
     bool filterAcceptsRow(int source_row, const QModelIndex & source_parent) const override;
 
@@ -60,7 +55,6 @@ class TransactionFilterProxy : public QSortFilterProxyModel
     quint32 typeFilter;
     WatchOnlyFilter watchOnlyFilter{WatchOnlyFilter_All};
     CAmount minAmount{0};
-    int limitRows{-1};
     bool showInactive{true};
 };