Merge bitcoin-core/gui#598: Avoid recalculating the wallet balance - use model cache

4584d300a40bfd84517072f7a6eee114fb7cab08 GUI: remove now unneeded 'm_balances' field from overviewpage (furszy)
050e8b139145d6991e740b0e5f2b3364663dd348 GUI: 'getAvailableBalance', use cached balance if the user did not select UTXO manually (furszy)
96e3264a82c51b456703f500bd98e8cb98115697 GUI: use cached balance in overviewpage and sendcoinsdialog (furszy)
321335bf0292034d79afa6c44f7f072942b6cc3c GUI: add getter for WalletModel::m_cached_balances field (furszy)
e62958dc81d215a1c56318d0914dfd9a33d45973 GUI: sendCoinsDialog, remove duplicate wallet().getBalances() call (furszy)

Pull request description:

  As per the title says, we are recalculating the entire wallet balance on different situations calling to `wallet().getBalances()`, when should instead make use of the wallet model cached balance.

  This has the benefits of (1) not spending resources calculating a balance that we already have cached, and (2) avoid blocking the main thread for a long time, in case of big wallets, walking through the entire wallet's tx map more than what it's really needed.

  Changes:

  1) Fix: `SendCoinsDialog` was calling `wallet().getBalances()` twice during `setModel`.
  2) Use the cached balance if the user did not select any UTXO manually inside the wallet model `getAvailableBalance` call.

  -----------------------
  As an extra note, this work born in [#25005](https://github.com/bitcoin/bitcoin/pull/25005) but grew out of scope of it.

ACKs for top commit:
  jarolrod:
    ACK 4584d300a40bfd84517072f7a6eee114fb7cab08
  hebasto:
    re-ACK 4584d300a40bfd84517072f7a6eee114fb7cab08, only suggested changes and commit message formatting since my [recent](https://github.com/bitcoin-core/gui/pull/598#pullrequestreview-1071268192) review.

Tree-SHA512: 6633ce7f9a82a3e46e75aa7295df46c80a4cd4a9f3305427af203c9bc8670573fa8a1927f14a279260c488cc975a08d238faba2e9751588086fea1dcf8ea2b28

1 files changed, 10 insertions, 13 deletions

diff --git a/src/qt/overviewpage.cpp b/src/qt/overviewpage.cpp
index a8133f481e..85a3c36f39 100644
--- a/src/qt/overviewpage.cpp
+++ b/src/qt/overviewpage.cpp
@@ -147,8 +147,6 @@ OverviewPage::OverviewPage(const PlatformStyle *platformStyle, QWidget *parent)
 {
     ui->setupUi(this);
 
-    m_balances.balance = -1;
-
     // use a SingleColorIcon for the "out of sync warning" icon
     QIcon icon = m_platform_style->SingleColorIcon(QStringLiteral(":/icons/warning"));
     ui->labelTransactionsStatus->setIcon(icon);
@@ -177,8 +175,9 @@ void OverviewPage::handleTransactionClicked(const QModelIndex &index)
 void OverviewPage::setPrivacy(bool privacy)
 {
     m_privacy = privacy;
-    if (m_balances.balance != -1) {
-        setBalance(m_balances);
+    const auto& balances = walletModel->getCachedBalance();
+    if (balances.balance != -1) {
+        setBalance(balances);
     }
 
     ui->listTransactions->setVisible(!m_privacy);
@@ -197,7 +196,6 @@ OverviewPage::~OverviewPage()
 void OverviewPage::setBalance(const interfaces::WalletBalances& balances)
 {
     BitcoinUnit unit = walletModel->getOptionsModel()->getDisplayUnit();
-    m_balances = balances;
     if (walletModel->wallet().isLegacy()) {
         if (walletModel->wallet().privateKeysDisabled()) {
             ui->labelBalance->setText(BitcoinUnits::formatWithPrivacy(unit, balances.watch_only_balance, BitcoinUnits::SeparatorStyle::ALWAYS, m_privacy));
@@ -276,14 +274,13 @@ void OverviewPage::setWalletModel(WalletModel *model)
         ui->listTransactions->setModelColumn(TransactionTableModel::ToAddress);
 
         // Keep up to date with wallet
-        interfaces::Wallet& wallet = model->wallet();
-        interfaces::WalletBalances balances = wallet.getBalances();
-        setBalance(balances);
+        setBalance(model->getCachedBalance());
         connect(model, &WalletModel::balanceChanged, this, &OverviewPage::setBalance);
 
         connect(model->getOptionsModel(), &OptionsModel::displayUnitChanged, this, &OverviewPage::updateDisplayUnit);
 
-        updateWatchOnlyLabels(wallet.haveWatchOnly() && !model->wallet().privateKeysDisabled());
+        interfaces::Wallet& wallet = model->wallet();
+        updateWatchOnlyLabels(wallet.haveWatchOnly() && !wallet.privateKeysDisabled());
         connect(model, &WalletModel::notifyWatchonlyChanged, [this](bool showWatchOnly) {
             updateWatchOnlyLabels(showWatchOnly && !walletModel->wallet().privateKeysDisabled());
         });
@@ -306,10 +303,10 @@ void OverviewPage::changeEvent(QEvent* e)
 
 void OverviewPage::updateDisplayUnit()
 {
-    if(walletModel && walletModel->getOptionsModel())
-    {
-        if (m_balances.balance != -1) {
-            setBalance(m_balances);
+    if (walletModel && walletModel->getOptionsModel()) {
+        const auto& balances = walletModel->getCachedBalance();
+        if (balances.balance != -1) {
+            setBalance(balances);
         }
 
         // Update txdelegate->unit with the current unit