From d5c36ce0c4b92ee7a2b5f256ec5f73cd1c95d21d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Barbosa?= <joao.paulo.barbosa@gmail.com>
Date: Mon, 14 Oct 2019 20:46:34 +0100
Subject: gui: Make polling in ClientModel asynchronous

With this change polling runs in a different thread to prevent
disturbing the event loop.

Github-Pull: #17135
Rebased-From: 6b6be41c36e4fe9a74bed50e7f0a06532ab1260b
---
 src/qt/clientmodel.cpp | 31 +++++++++++++++++++------------
 src/qt/clientmodel.h   |  4 ++--
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/src/qt/clientmodel.cpp b/src/qt/clientmodel.cpp
index 238be08480..5b216b2705 100644
--- a/src/qt/clientmodel.cpp
+++ b/src/qt/clientmodel.cpp
@@ -19,6 +19,7 @@
 #include <stdint.h>
 
 #include <QDebug>
+#include <QThread>
 #include <QTimer>
 
 static int64_t nLastHeaderTipUpdateNotification = 0;
@@ -30,15 +31,26 @@ ClientModel::ClientModel(interfaces::Node& node, OptionsModel *_optionsModel, QO
     optionsModel(_optionsModel),
     peerTableModel(nullptr),
     banTableModel(nullptr),
-    pollTimer(nullptr)
+    m_thread(new QThread(this))
 {
     cachedBestHeaderHeight = -1;
     cachedBestHeaderTime = -1;
     peerTableModel = new PeerTableModel(m_node, this);
     banTableModel = new BanTableModel(m_node, this);
-    pollTimer = new QTimer(this);
-    connect(pollTimer, &QTimer::timeout, this, &ClientModel::updateTimer);
-    pollTimer->start(MODEL_UPDATE_DELAY);
+
+    QTimer* timer = new QTimer;
+    timer->setInterval(MODEL_UPDATE_DELAY);
+    connect(timer, &QTimer::timeout, [this] {
+        // no locking required at this point
+        // the following calls will acquire the required lock
+        Q_EMIT mempoolSizeChanged(m_node.getMempoolSize(), m_node.getMempoolDynamicUsage());
+        Q_EMIT bytesChanged(m_node.getTotalBytesRecv(), m_node.getTotalBytesSent());
+    });
+    connect(m_thread, &QThread::finished, timer, &QObject::deleteLater);
+    connect(m_thread, &QThread::started, [timer] { timer->start(); });
+    // move timer to thread so that polling doesn't disturb main event loop
+    timer->moveToThread(m_thread);
+    m_thread->start();
 
     subscribeToCoreSignals();
 }
@@ -46,6 +58,9 @@ ClientModel::ClientModel(interfaces::Node& node, OptionsModel *_optionsModel, QO
 ClientModel::~ClientModel()
 {
     unsubscribeFromCoreSignals();
+
+    m_thread->quit();
+    m_thread->wait();
 }
 
 int ClientModel::getNumConnections(unsigned int flags) const
@@ -90,14 +105,6 @@ int64_t ClientModel::getHeaderTipTime() const
     return cachedBestHeaderTime;
 }
 
-void ClientModel::updateTimer()
-{
-    // no locking required at this point
-    // the following calls will acquire the required lock
-    Q_EMIT mempoolSizeChanged(m_node.getMempoolSize(), m_node.getMempoolDynamicUsage());
-    Q_EMIT bytesChanged(m_node.getTotalBytesRecv(), m_node.getTotalBytesSent());
-}
-
 void ClientModel::updateNumConnections(int numConnections)
 {
     Q_EMIT numConnectionsChanged(numConnections);
diff --git a/src/qt/clientmodel.h b/src/qt/clientmodel.h
index 95f4521f06..d3a95d531e 100644
--- a/src/qt/clientmodel.h
+++ b/src/qt/clientmodel.h
@@ -90,7 +90,8 @@ private:
     PeerTableModel *peerTableModel;
     BanTableModel *banTableModel;
 
-    QTimer *pollTimer;
+    //! A thread to interact with m_node asynchronously
+    QThread* const m_thread;
 
     void subscribeToCoreSignals();
     void unsubscribeFromCoreSignals();
@@ -110,7 +111,6 @@ Q_SIGNALS:
     void showProgress(const QString &title, int nProgress);
 
 public Q_SLOTS:
-    void updateTimer();
     void updateNumConnections(int numConnections);
     void updateNetworkActive(bool networkActive);
     void updateAlert();
-- 
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