Merge bitcoin-core/gui#97: Relax GUI freezes during IBD (when using wallets)

0d9d2a1f7c26dc9c7b233ea8c3182fe1f8936bca Only update the updateSmartFeeLabel once in sync (Jonas Schnelli)

Pull request description:

  Calling `updateSmartFeeLabel` and therefore `estimateSmartFee` is pointless during IBD.

  GUI freezes appear because `estimateSmartFee` competes with `processBlock` for the `m_cs_fee_estimator` lock leading to multiple seconds of blocking the GUI thread in `updateSmartFeeLabel`.

ACKs for top commit:
  ryanofsky:
    Code review ACK 0d9d2a1f7c26dc9c7b233ea8c3182fe1f8936bca. Clever fix. Didn't test but I remember I could reproduce the startup issue easily before by putting a sleep in estimateSmartFee.
  promag:
    Code review ACK 0d9d2a1f7c26dc9c7b233ea8c3182fe1f8936bca.
  hebasto:
    ACK 0d9d2a1f7c26dc9c7b233ea8c3182fe1f8936bca, tested on Linux Mint 20 (x86_64) with `QT_FATAL_WARNINGS=1` and `-debug=qt`.

Tree-SHA512: 85ec2266f06ddd7b523e24d2a462f10ed965d5b4d479005263056f81b7fe49996e1568dafb84658af406e9202ed3bfa846d59c10bb951e0f97cee230e30fafd5

2 files changed, 11 insertions, 1 deletions

diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index 97fb88d71c..50a1ea6936 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -28,6 +28,8 @@
 #include <wallet/fees.h>
 #include <wallet/wallet.h>
 
+#include <validation.h>
+
 #include <QFontMetrics>
 #include <QScrollBar>
 #include <QSettings>
@@ -134,7 +136,7 @@ void SendCoinsDialog::setClientModel(ClientModel *_clientModel)
     this->clientModel = _clientModel;
 
     if (_clientModel) {
-        connect(_clientModel, &ClientModel::numBlocksChanged, this, &SendCoinsDialog::updateSmartFeeLabel);
+        connect(_clientModel, &ClientModel::numBlocksChanged, this, &SendCoinsDialog::updateNumberOfBlocks);
     }
 }
 
@@ -744,6 +746,12 @@ void SendCoinsDialog::updateCoinControlState(CCoinControl& ctrl)
     ctrl.fAllowWatchOnly = model->wallet().privateKeysDisabled();
 }
 
+void SendCoinsDialog::updateNumberOfBlocks(int count, const QDateTime& blockDate, double nVerificationProgress, bool headers, SynchronizationState sync_state) {
+    if (sync_state == SynchronizationState::POST_INIT) {
+        updateSmartFeeLabel();
+    }
+}
+
 void SendCoinsDialog::updateSmartFeeLabel()
 {
     if(!model || !model->getOptionsModel())
diff --git a/src/qt/sendcoinsdialog.h b/src/qt/sendcoinsdialog.h
index 6961aa7821..8519f1f65b 100644
--- a/src/qt/sendcoinsdialog.h
+++ b/src/qt/sendcoinsdialog.h
@@ -17,6 +17,7 @@ class ClientModel;
 class PlatformStyle;
 class SendCoinsEntry;
 class SendCoinsRecipient;
+enum class SynchronizationState;
 
 namespace Ui {
     class SendCoinsDialog;
@@ -98,6 +99,7 @@ private Q_SLOTS:
     void coinControlClipboardLowOutput();
     void coinControlClipboardChange();
     void updateFeeSectionControls();
+    void updateNumberOfBlocks(int count, const QDateTime& blockDate, double nVerificationProgress, bool headers, SynchronizationState sync_state);
     void updateSmartFeeLabel();
 
 Q_SIGNALS: