Notify the GUI that the keypool has changed to set the receive button

Whenever the keypool changes (new keys generated, new seed set,
keypool runs out, etc.), notify the GUI that the keypool has changed. The
receive button can then be enabled and disabled as necessary.

src/interfaces/wallet.cpp

@@ -488,6 +488,10 @@ class WalletImpl : public Wallet
     {
         return MakeHandler(m_wallet.NotifyWatchonlyChanged.connect(fn));
     }
+    std::unique_ptr<Handler> handleCanGetAddressesChanged(CanGetAddressesChangedFn fn) override
+    {
+        return MakeHandler(m_wallet.NotifyCanGetAddressesChanged.connect(fn));
+    }
 
     std::shared_ptr<CWallet> m_shared_wallet;
     CWallet& m_wallet;

src/interfaces/wallet.h

@@ -271,6 +271,10 @@ class Wallet
     //! Register handler for watchonly changed messages.
     using WatchOnlyChangedFn = std::function<void(bool have_watch_only)>;
     virtual std::unique_ptr<Handler> handleWatchOnlyChanged(WatchOnlyChangedFn fn) = 0;
+
+    //! Register handler for keypool changed messages.
+    using CanGetAddressesChangedFn = std::function<void()>;
+    virtual std::unique_ptr<Handler> handleCanGetAddressesChanged(CanGetAddressesChangedFn fn) = 0;
 };
 
 //! Tracking object returned by CreateTransaction and passed to CommitTransaction.

src/qt/receivecoinsdialog.cpp

@@ -100,8 +100,13 @@ void ReceiveCoinsDialog::setModel(WalletModel *_model)
             ui->useBech32->setCheckState(Qt::Unchecked);
         }
 
-        // eventually disable the main receive button if private key operations are disabled
+        // Set the button to be enabled or disabled based on whether the wallet can give out new addresses.
         ui->receiveButton->setEnabled(model->canGetAddresses());
+
+        // Enable/disable the receive button if the wallet is now able/unable to give out new addresses.
+        connect(model, &WalletModel::canGetAddressesChanged, [this] {
+            ui->receiveButton->setEnabled(model->canGetAddresses());
+        });
     }
 }
 

src/qt/walletmodel.cpp

@@ -423,6 +423,11 @@ static void NotifyWatchonlyChanged(WalletModel *walletmodel, bool fHaveWatchonly
                               Q_ARG(bool, fHaveWatchonly));
 }
 
+static void NotifyCanGetAddressesChanged(WalletModel* walletmodel)
+{
+    QMetaObject::invokeMethod(walletmodel, "canGetAddressesChanged");
+}
+
 void WalletModel::subscribeToCoreSignals()
 {
     // Connect signals to wallet
@@ -432,6 +437,7 @@ void WalletModel::subscribeToCoreSignals()
     m_handler_transaction_changed = m_wallet->handleTransactionChanged(std::bind(NotifyTransactionChanged, this, std::placeholders::_1, std::placeholders::_2));
     m_handler_show_progress = m_wallet->handleShowProgress(std::bind(ShowProgress, this, std::placeholders::_1, std::placeholders::_2));
     m_handler_watch_only_changed = m_wallet->handleWatchOnlyChanged(std::bind(NotifyWatchonlyChanged, this, std::placeholders::_1));
+    m_handler_can_get_addrs_changed = m_wallet->handleCanGetAddressesChanged(boost::bind(NotifyCanGetAddressesChanged, this));
 }
 
 void WalletModel::unsubscribeFromCoreSignals()
@@ -443,6 +449,7 @@ void WalletModel::unsubscribeFromCoreSignals()
     m_handler_transaction_changed->disconnect();
     m_handler_show_progress->disconnect();
     m_handler_watch_only_changed->disconnect();
+    m_handler_can_get_addrs_changed->disconnect();
 }
 
 // WalletModel::UnlockContext implementation
@@ -573,6 +580,11 @@ bool WalletModel::privateKeysDisabled() const
 
 bool WalletModel::canGetAddresses() const
 {
+    // The wallet can provide a fresh address if:
+    // * hdEnabled(): an HD seed is present; or
+    // * it is a legacy wallet, because:
+    //     * !hdEnabled(): an HD seed is not present; and
+    //     * !IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS): private keys have not been disabled (which results in hdEnabled() == true)
     return m_wallet->hdEnabled() || (!m_wallet->hdEnabled() && !m_wallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
 }
 

src/qt/walletmodel.h

@@ -233,6 +233,7 @@ class WalletModel : public QObject
     std::unique_ptr<interfaces::Handler> m_handler_transaction_changed;
     std::unique_ptr<interfaces::Handler> m_handler_show_progress;
     std::unique_ptr<interfaces::Handler> m_handler_watch_only_changed;
+    std::unique_ptr<interfaces::Handler> m_handler_can_get_addrs_changed;
     interfaces::Node& m_node;
 
     bool fHaveWatchOnly;
@@ -284,6 +285,9 @@ class WalletModel : public QObject
     // Signal that wallet is about to be removed
     void unload();
 
+    // Notify that there are now keys in the keypool
+    void canGetAddressesChanged();
+
 public Q_SLOTS:
     /* Wallet status might have changed */
     void updateStatus();

src/wallet/wallet.cpp

@@ -1403,6 +1403,7 @@ void CWallet::SetHDSeed(const CPubKey& seed)
     newHdChain.nVersion = CanSupportFeature(FEATURE_HD_SPLIT) ? CHDChain::VERSION_HD_CHAIN_SPLIT : CHDChain::VERSION_HD_BASE;
     newHdChain.seed_id = seed.GetID();
     SetHDChain(newHdChain, false);
+    NotifyCanGetAddressesChanged();
 }
 
 void CWallet::SetHDChain(const CHDChain& chain, bool memonly)
@@ -3327,6 +3328,7 @@ bool CWallet::TopUpKeyPool(unsigned int kpSize)
             WalletLogPrintf("keypool added %d keys (%d internal), size=%u (%u internal)\n", missingInternal + missingExternal, missingInternal, setInternalKeyPool.size() + setExternalKeyPool.size() + set_pre_split_keypool.size(), setInternalKeyPool.size());
         }
     }
+    NotifyCanGetAddressesChanged();
     return true;
 }
 
@@ -3371,6 +3373,7 @@ bool CWallet::ReserveKeyFromKeyPool(int64_t& nIndex, CKeyPool& keypool, bool fRe
         m_pool_key_to_index.erase(keypool.vchPubKey.GetID());
         WalletLogPrintf("keypool reserve %d\n", nIndex);
     }
+    NotifyCanGetAddressesChanged();
     return true;
 }
 
@@ -3395,6 +3398,7 @@ void CWallet::ReturnKey(int64_t nIndex, bool fInternal, const CPubKey& pubkey)
             setExternalKeyPool.insert(nIndex);
         }
         m_pool_key_to_index[pubkey.GetID()] = nIndex;
+        NotifyCanGetAddressesChanged();
     }
     WalletLogPrintf("keypool return %d\n", nIndex);
 }

src/wallet/wallet.h

@@ -1087,6 +1087,9 @@ class CWallet final : public CCryptoKeyStore, public CValidationInterface
     /** Watch-only address added */
     boost::signals2::signal<void (bool fHaveWatchOnly)> NotifyWatchonlyChanged;
 
+    /** Keypool has new keys */
+    boost::signals2::signal<void ()> NotifyCanGetAddressesChanged;
+
     /** Inquire whether this wallet broadcasts transactions. */
     bool GetBroadcastTransactions() const { return fBroadcastTransactions; }
     /** Set whether this wallet broadcasts transactions. */