suggestion bitcoin#16963 (comment)

src/interfaces/chain.cpp

@@ -339,7 +339,6 @@ class ChainImpl : public Chain
     void initMessage(const std::string& message) override { ::uiInterface.InitMessage(message); }
     void initWarning(const std::string& message) override { InitWarning(message); }
     void initError(const std::string& message) override { InitError(message); }
-    void loadWallet(std::unique_ptr<Wallet> wallet) override { ::uiInterface.LoadWallet(wallet); }
     void showProgress(const std::string& title, int progress, bool resume_possible) override
     {
         ::uiInterface.ShowProgress(title, progress, resume_possible);

src/interfaces/chain.h

@@ -43,7 +43,7 @@ class Wallet;
 //!   asynchronously
 //!   (https://github.com/bitcoin/bitcoin/pull/10973#issuecomment-380101269).
 //!
-//! * The initMessages() and loadWallet() methods which the wallet uses to send
+//! * The initMessage() and showProgress() methods which the wallet uses to send
 //!   notifications to the GUI should go away when GUI and wallet can directly
 //!   communicate with each other without going through the node
 //!   (https://github.com/bitcoin/bitcoin/pull/15288#discussion_r253321096).
@@ -208,9 +208,6 @@ class Chain
     //! Send init error.
     virtual void initError(const std::string& message) = 0;
 
-    //! Send wallet load notification to the GUI.
-    virtual void loadWallet(std::unique_ptr<Wallet> wallet) = 0;
-
     //! Send progress indicator.
     virtual void showProgress(const std::string& title, int progress, bool resume_possible) = 0;
 

src/interfaces/handler.cpp

@@ -22,11 +22,25 @@ class HandlerImpl : public Handler
     boost::signals2::scoped_connection m_connection;
 };
 
+class CleanupHandler : public Handler
+{
+public:
+    explicit CleanupHandler(std::function<void()> cleanup) : m_cleanup(std::move(cleanup)) {}
+    ~CleanupHandler() override { if (!m_cleanup) return; m_cleanup(); m_cleanup = nullptr; }
+    void disconnect() override { if (!m_cleanup) return; m_cleanup(); m_cleanup = nullptr; }
+    std::function<void()> m_cleanup;
+};
+
 } // namespace
 
 std::unique_ptr<Handler> MakeHandler(boost::signals2::connection connection)
 {
     return MakeUnique<HandlerImpl>(std::move(connection));
 }
 
+std::unique_ptr<Handler> MakeHandler(std::function<void()> cleanup)
+{
+    return MakeUnique<CleanupHandler>(std::move(cleanup));
+}
+
 } // namespace interfaces

src/interfaces/handler.h

@@ -5,6 +5,7 @@
 #ifndef BITCOIN_INTERFACES_HANDLER_H
 #define BITCOIN_INTERFACES_HANDLER_H
 
+#include <functional>
 #include <memory>
 
 namespace boost {
@@ -30,6 +31,9 @@ class Handler
 //! Return handler wrapping a boost signal connection.
 std::unique_ptr<Handler> MakeHandler(boost::signals2::connection connection);
 
+//! Return handler wrapping a cleanup function.
+std::unique_ptr<Handler> MakeHandler(std::function<void()> cleanup);
+
 } // namespace interfaces
 
 #endif // BITCOIN_INTERFACES_HANDLER_H

src/interfaces/node.cpp

@@ -45,11 +45,10 @@ std::vector<fs::path> ListWalletDir();
 std::vector<std::shared_ptr<CWallet>> GetWallets();
 std::shared_ptr<CWallet> LoadWallet(interfaces::Chain& chain, const std::string& name, std::string& error, std::string& warning);
 WalletCreationStatus CreateWallet(interfaces::Chain& chain, const SecureString& passphrase, uint64_t wallet_creation_flags, const std::string& name, std::string& error, std::string& warning, std::shared_ptr<CWallet>& result);
+std::unique_ptr<interfaces::Handler> HandleLoadWallet(interfaces::Node::LoadWalletFn load_wallet);
 
 namespace interfaces {
 
-class Wallet;
-
 namespace {
 
 class NodeImpl : public Node
@@ -286,7 +285,7 @@ class NodeImpl : public Node
     }
     std::unique_ptr<Handler> handleLoadWallet(LoadWalletFn fn) override
     {
-        return MakeHandler(::uiInterface.LoadWallet_connect([fn](std::unique_ptr<Wallet>& wallet) { fn(std::move(wallet)); }));
+        return HandleLoadWallet(std::move(fn));
     }
     std::unique_ptr<Handler> handleNotifyNumConnectionsChanged(NotifyNumConnectionsChangedFn fn) override
     {

src/ui_interface.cpp

@@ -16,7 +16,6 @@ struct UISignals {
     boost::signals2::signal<CClientUIInterface::NotifyNumConnectionsChangedSig> NotifyNumConnectionsChanged;
     boost::signals2::signal<CClientUIInterface::NotifyNetworkActiveChangedSig> NotifyNetworkActiveChanged;
     boost::signals2::signal<CClientUIInterface::NotifyAlertChangedSig> NotifyAlertChanged;
-    boost::signals2::signal<CClientUIInterface::LoadWalletSig> LoadWallet;
     boost::signals2::signal<CClientUIInterface::ShowProgressSig> ShowProgress;
     boost::signals2::signal<CClientUIInterface::NotifyBlockTipSig> NotifyBlockTip;
     boost::signals2::signal<CClientUIInterface::NotifyHeaderTipSig> NotifyHeaderTip;
@@ -36,7 +35,6 @@ ADD_SIGNALS_IMPL_WRAPPER(InitMessage);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyNumConnectionsChanged);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyNetworkActiveChanged);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyAlertChanged);
-ADD_SIGNALS_IMPL_WRAPPER(LoadWallet);
 ADD_SIGNALS_IMPL_WRAPPER(ShowProgress);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyBlockTip);
 ADD_SIGNALS_IMPL_WRAPPER(NotifyHeaderTip);
@@ -48,7 +46,6 @@ void CClientUIInterface::InitMessage(const std::string& message) { return g_ui_s
 void CClientUIInterface::NotifyNumConnectionsChanged(int newNumConnections) { return g_ui_signals.NotifyNumConnectionsChanged(newNumConnections); }
 void CClientUIInterface::NotifyNetworkActiveChanged(bool networkActive) { return g_ui_signals.NotifyNetworkActiveChanged(networkActive); }
 void CClientUIInterface::NotifyAlertChanged() { return g_ui_signals.NotifyAlertChanged(); }
-void CClientUIInterface::LoadWallet(std::unique_ptr<interfaces::Wallet>& wallet) { return g_ui_signals.LoadWallet(wallet); }
 void CClientUIInterface::ShowProgress(const std::string& title, int nProgress, bool resume_possible) { return g_ui_signals.ShowProgress(title, nProgress, resume_possible); }
 void CClientUIInterface::NotifyBlockTip(bool b, const CBlockIndex* i) { return g_ui_signals.NotifyBlockTip(b, i); }
 void CClientUIInterface::NotifyHeaderTip(bool b, const CBlockIndex* i) { return g_ui_signals.NotifyHeaderTip(b, i); }

src/ui_interface.h

@@ -18,10 +18,6 @@ class connection;
 }
 } // namespace boost
 
-namespace interfaces {
-class Wallet;
-} // namespace interfaces
-
 /** General change type (added, updated, removed). */
 enum ChangeType
 {
@@ -106,9 +102,6 @@ class CClientUIInterface
      */
     ADD_SIGNALS_DECL_WRAPPER(NotifyAlertChanged, void, );
 
-    /** A wallet has been loaded. */
-    ADD_SIGNALS_DECL_WRAPPER(LoadWallet, void, std::unique_ptr<interfaces::Wallet>& wallet);
-
     /**
      * Show progress e.g. for verifychain.
      * resume_possible indicates shutting down now will result in the current progress action resuming upon restart.

src/wallet/wallet.cpp

@@ -49,6 +49,7 @@ static const size_t OUTPUT_GROUP_MAX_ENTRIES = 10;
 
 static CCriticalSection cs_wallets;
 static std::vector<std::shared_ptr<CWallet>> vpwallets GUARDED_BY(cs_wallets);
+static std::list<LoadWalletFn> g_load_wallet_fns GUARDED_BY(cs_wallets);
 
 bool AddWallet(const std::shared_ptr<CWallet>& wallet)
 {
@@ -91,6 +92,13 @@ std::shared_ptr<CWallet> GetWallet(const std::string& name)
     return nullptr;
 }
 
+std::unique_ptr<interfaces::Handler> HandleLoadWallet(LoadWalletFn load_wallet)
+{
+    LOCK(cs_wallets);
+    auto it = g_load_wallet_fns.emplace(g_load_wallet_fns.end(), std::move(load_wallet));
+    return interfaces::MakeHandler([it] { LOCK(cs_wallets); g_load_wallet_fns.erase(it); });
+}
+
 static Mutex g_wallet_release_mutex;
 static std::condition_variable g_wallet_release_cv;
 static std::set<std::string> g_unloading_wallet_set;

src/wallet/wallet.h

@@ -36,6 +36,8 @@
 
 #include <boost/signals2/signal.hpp>
 
+using LoadWalletFn = std::function<void(std::unique_ptr<interfaces::Wallet> wallet)>;
+
 //! Explicitly unload and delete the wallet.
 //! Blocks the current thread after signaling the unload intent so that all
 //! wallet clients release the wallet.
@@ -49,6 +51,7 @@ bool HasWallets();
 std::vector<std::shared_ptr<CWallet>> GetWallets();
 std::shared_ptr<CWallet> GetWallet(const std::string& name);
 std::shared_ptr<CWallet> LoadWallet(interfaces::Chain& chain, const WalletLocation& location, std::string& error, std::string& warning);
+std::unique_ptr<interfaces::Handler> HandleLoadWallet(LoadWalletFn load_wallet);
 
 enum class WalletCreationStatus {
     SUCCESS,