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, 5 insertions, 7 deletions

diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index bd44d12781..a75c1098a5 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -164,11 +164,9 @@ void SendCoinsDialog::setModel(WalletModel *_model)
             }
         }
 
-        interfaces::WalletBalances balances = _model->wallet().getBalances();
-        setBalance(balances);
         connect(_model, &WalletModel::balanceChanged, this, &SendCoinsDialog::setBalance);
-        connect(_model->getOptionsModel(), &OptionsModel::displayUnitChanged, this, &SendCoinsDialog::updateDisplayUnit);
-        updateDisplayUnit();
+        connect(_model->getOptionsModel(), &OptionsModel::displayUnitChanged, this, &SendCoinsDialog::refreshBalance);
+        refreshBalance();
 
         // Coin Control
         connect(_model->getOptionsModel(), &OptionsModel::displayUnitChanged, this, &SendCoinsDialog::coinControlUpdateLabels);
@@ -711,9 +709,9 @@ void SendCoinsDialog::setBalance(const interfaces::WalletBalances& balances)
     }
 }
 
-void SendCoinsDialog::updateDisplayUnit()
+void SendCoinsDialog::refreshBalance()
 {
-    setBalance(model->wallet().getBalances());
+    setBalance(model->getCachedBalance());
     ui->customFee->setDisplayUnit(model->getOptionsModel()->getDisplayUnit());
     updateSmartFeeLabel();
 }
@@ -786,7 +784,7 @@ void SendCoinsDialog::useAvailableBalance(SendCoinsEntry* entry)
     m_coin_control->fAllowWatchOnly = model->wallet().privateKeysDisabled() && !model->wallet().hasExternalSigner();
 
     // Calculate available amount to send.
-    CAmount amount = model->wallet().getAvailableBalance(*m_coin_control);
+    CAmount amount = model->getAvailableBalance(m_coin_control.get());
     for (int i = 0; i < ui->entries->count(); ++i) {
         SendCoinsEntry* e = qobject_cast<SendCoinsEntry*>(ui->entries->itemAt(i)->widget());
         if (e && !e->isHidden() && e != entry) {