gui: Fix start timer from non QThread

src/qt/walletcontroller.cpp

@@ -108,6 +108,12 @@ WalletModel* WalletController::getOrCreateWallet(std::unique_ptr<interfaces::Wal
     wallet_model->setParent(this);
     m_wallets.push_back(wallet_model);
 
+    // WalletModel::startPollBalance needs to be called in a thread managed by
+    // Qt because of startTimer. Considering the current thread can be a RPC
+    // thread, better delegate the calling to Qt with Qt::AutoConnection.
+    const bool called = QMetaObject::invokeMethod(wallet_model, "startPollBalance");
+    assert(called);
+
     connect(wallet_model, &WalletModel::unload, [this, wallet_model] {
         // Defer removeAndDeleteWallet when no modal widget is active.
         // TODO: remove this workaround by removing usage of QDiallog::exec.

src/qt/walletmodel.cpp

@@ -44,11 +44,6 @@ WalletModel::WalletModel(std::unique_ptr<interfaces::Wallet> wallet, interfaces:
     transactionTableModel = new TransactionTableModel(platformStyle, this);
     recentRequestsTableModel = new RecentRequestsTableModel(this);
 
-    // This timer will be fired repeatedly to update the balance
-    pollTimer = new QTimer(this);
-    connect(pollTimer, &QTimer::timeout, this, &WalletModel::pollBalanceChanged);
-    pollTimer->start(MODEL_UPDATE_DELAY);
-
     subscribeToCoreSignals();
 }
 
@@ -57,6 +52,14 @@ WalletModel::~WalletModel()
     unsubscribeFromCoreSignals();
 }
 
+void WalletModel::startPollBalance()
+{
+    // This timer will be fired repeatedly to update the balance
+    QTimer* timer = new QTimer(this);
+    connect(timer, &QTimer::timeout, this, &WalletModel::pollBalanceChanged);
+    timer->start(MODEL_UPDATE_DELAY);
+}
+
 void WalletModel::updateStatus()
 {
     EncryptionStatus newEncryptionStatus = getEncryptionStatus();

src/qt/walletmodel.h

@@ -255,8 +255,6 @@ private:
     EncryptionStatus cachedEncryptionStatus;
     int cachedNumBlocks;
 
-    QTimer *pollTimer;
-
     void subscribeToCoreSignals();
     void unsubscribeFromCoreSignals();
     void checkBalanceChanged(const interfaces::WalletBalances& new_balances);
@@ -292,6 +290,9 @@ Q_SIGNALS:
     void canGetAddressesChanged();
 
 public Q_SLOTS:
+    /* Starts a timer to periodically update the balance */
+    void startPollBalance();
+
     /* Wallet status might have changed */
     void updateStatus();
     /* New transaction, or transaction changed status */