From d325799acdd8d010d5e4b2f77d9cc67d76d4ad28 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Thu, 24 Dec 2020 16:55:39 +0200
Subject: [PATCH] qt: Handle peer addition/removal in a right way

This change fixes a bug when a multiple rows selection gets inconsistent
after a peer addition/removal.
---
 src/qt/peertablemodel.cpp | 29 ++++++++++++++++++++++++++---
 src/qt/peertablemodel.h   |  3 +++
 src/qt/rpcconsole.cpp     |  2 +-
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/src/qt/peertablemodel.cpp b/src/qt/peertablemodel.cpp
index a61b9f90b01..68ec45173ce 100644
--- a/src/qt/peertablemodel.cpp
+++ b/src/qt/peertablemodel.cpp
@@ -147,7 +147,30 @@ void PeerTableModel::refresh()
         new_peers_data.append(stats);
     }
 
-    Q_EMIT layoutAboutToBeChanged();
-    m_peers_data.swap(new_peers_data);
-    Q_EMIT layoutChanged();
+    // Handle a new peer addition or an old peer in a right way. See:
+    // - https://doc.qt.io/qt-5/model-view-programming.html#inserting-and-removing-rows
+    // - https://doc.qt.io/qt-5/model-view-programming.html#resizable-models
+    // We use the fact that interfaces::Node::getNodesStats
+    // returns std::vector naturally sorted by nodeid.
+    for (int i = 0; i < m_peers_data.size();) {
+        if (i < new_peers_data.size() && m_peers_data.at(i).nodeStats.nodeid == new_peers_data.at(i).nodeStats.nodeid) {
+            ++i;
+            continue;
+        }
+        // A peer has been removed from the table.
+        beginRemoveRows(QModelIndex(), i, i);
+        m_peers_data.erase(m_peers_data.begin() + i);
+        endRemoveRows();
+    }
+
+    if (m_peers_data.size() < new_peers_data.size()) {
+        // Some peers have been added to the end of the table.
+        beginInsertRows(QModelIndex(), m_peers_data.size(), new_peers_data.size() - 1);
+        m_peers_data.swap(new_peers_data);
+        endInsertRows();
+    } else {
+        m_peers_data.swap(new_peers_data);
+    }
+
+    Q_EMIT changed();
 }
diff --git a/src/qt/peertablemodel.h b/src/qt/peertablemodel.h
index 2cf3f514720..3ebecc031ee 100644
--- a/src/qt/peertablemodel.h
+++ b/src/qt/peertablemodel.h
@@ -72,6 +72,9 @@ class PeerTableModel : public QAbstractTableModel
 public Q_SLOTS:
     void refresh();
 
+Q_SIGNALS:
+    void changed();
+
 private:
     //! Internal peer data structure.
     QList<CNodeCombinedStats> m_peers_data{};
diff --git a/src/qt/rpcconsole.cpp b/src/qt/rpcconsole.cpp
index 795db5baad2..98ae89bccf9 100644
--- a/src/qt/rpcconsole.cpp
+++ b/src/qt/rpcconsole.cpp
@@ -623,7 +623,7 @@ void RPCConsole::setClientModel(ClientModel *model, int bestblock_height, int64_
 
         // peer table signal handling - update peer details when selecting new node
         connect(ui->peerWidget->selectionModel(), &QItemSelectionModel::selectionChanged, this, &RPCConsole::updateDetailWidget);
-        connect(model->getPeerTableModel(), &PeerTableModel::layoutChanged, this, &RPCConsole::updateDetailWidget);
+        connect(model->getPeerTableModel(), &PeerTableModel::changed, this, &RPCConsole::updateDetailWidget);
 
         // set up ban table
         ui->banlistWidget->setModel(model->getBanTableModel());