gui: Extend address book filter for nested filtering

Extend AddressBookFilterProxyModel to allow using nested filters to be applied
on top of it. If future needs arise for similar filters outside the address book page,
the code could be easily refactored and moved in a new subclass of QSortFilterProxyModel,
perhaps with limits on nested levels.

For safety and performance reasons, the code of the filter proxy model class declaration
(in addressbookpage.h) and its instance creation were updated by aligning it with
TransactionFilterProxy in overviewpage.h as this addresses situations of unexpected crashes,
such as segfault on closing the app, double free or corruption, or stack smashing detection.

src/qt/addressbookpage.cpp

@@ -28,15 +28,31 @@
 class AddressBookSortFilterProxyModel final : public QSortFilterProxyModel
 {
     const QString m_type;
+    const bool m_nestedFilterEnabled;
 
 public:
-    AddressBookSortFilterProxyModel(const QString& type, QObject* parent)
+    AddressBookSortFilterProxyModel(const QString& type, QObject* parent, bool enableNestedFilter)
         : QSortFilterProxyModel(parent)
         , m_type(type)
+        , m_nestedFilterEnabled(enableNestedFilter)
     {
         setDynamicSortFilter(true);
         setFilterCaseSensitivity(Qt::CaseInsensitive);
         setSortCaseSensitivity(Qt::CaseInsensitive);
+
+        if (m_nestedFilterEnabled) {
+            nextedFilterProxyModel.reset(new AddressBookSortFilterProxyModel(type, this, false));
+            nextedFilterProxyModel->setSourceModel(this);
+        }
+    }
+
+    AddressBookSortFilterProxyModel* nestedProxyModel() const noexcept{
+        if (!m_nestedFilterEnabled) return const_cast<AddressBookSortFilterProxyModel*>(this);
+        return nextedFilterProxyModel.get();
+    }
+
+    bool isNestedFilterEnabled() const {
+        return m_nestedFilterEnabled;
     }
 
 protected:
@@ -66,6 +82,9 @@ class AddressBookSortFilterProxyModel final : public QSortFilterProxyModel
 
         return filterBy;
     }
+
+private:
+    std::unique_ptr<AddressBookSortFilterProxyModel> nextedFilterProxyModel{nullptr};
 };
 
 AddressBookPage::AddressBookPage(const PlatformStyle *platformStyle, Mode _mode, Tabs _tab, QWidget *parent) :
@@ -154,12 +173,12 @@ void AddressBookPage::setModel(AddressTableModel *_model)
         return;
 
     auto type = tab == ReceivingTab ? AddressTableModel::Receive : AddressTableModel::Send;
-    proxyModel = new AddressBookSortFilterProxyModel(type, this);
+    proxyModel.reset(new AddressBookSortFilterProxyModel(type, this, false));
     proxyModel->setSourceModel(_model);
 
-    connect(ui->searchLineEdit, &QLineEdit::textChanged, proxyModel, &QSortFilterProxyModel::setFilterWildcard);
+    connect(ui->searchLineEdit, &QLineEdit::textChanged, proxyModel.get(), &QSortFilterProxyModel::setFilterWildcard);
 
-    ui->tableView->setModel(proxyModel);
+    ui->tableView->setModel(proxyModel->nestedProxyModel());
     ui->tableView->sortByColumn(0, Qt::AscendingOrder);
 
     // Set column widths
@@ -308,7 +327,7 @@ void AddressBookPage::on_exportButton_clicked()
     CSVModelWriter writer(filename);
 
     // name, column, role
-    writer.setModel(proxyModel);
+    writer.setModel(proxyModel.get());
     writer.addColumn("Label", AddressTableModel::Label, Qt::EditRole);
     writer.addColumn("Address Type", AddressTableModel::Type, Qt::EditRole);
     writer.addColumn("Address", AddressTableModel::Address, Qt::EditRole);

src/qt/addressbookpage.h

@@ -53,7 +53,7 @@ public Q_SLOTS:
     Mode mode;
     Tabs tab;
     QString returnValue;
-    AddressBookSortFilterProxyModel *proxyModel;
+    std::unique_ptr<AddressBookSortFilterProxyModel> proxyModel{nullptr};
     QMenu *contextMenu;
     QString newAddressToSelect;