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()) {