From e89c09a62e3891abc6c85e79bc770ce1c8549ead Mon Sep 17 00:00:00 2001
From: Ismael Asensio <isma.af@gmail.com>
Date: Thu, 2 Mar 2023 00:38:03 +0100
Subject: [PATCH] TabBox: Avoid unnecesary resets of the client model

When the tabbox switcher is shown and any window is added or
removed, its client model is fully reset, even if this window
is not included in the model.

This can be a bit expensive and also produce small visual quirks
on certain switchers, so let's check if the window list changes
before resetting the model.

BUG: 466660
FIXED-IN: 5.27.3
---
 src/tabbox/clientmodel.cpp | 48 +++++++++++++++++++++++++-------------
 src/tabbox/clientmodel.h   |  8 +++----
 2 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/src/tabbox/clientmodel.cpp b/src/tabbox/clientmodel.cpp
index d6c6b1c91a..dd08bbef88 100644
--- a/src/tabbox/clientmodel.cpp
+++ b/src/tabbox/clientmodel.cpp
@@ -152,8 +152,9 @@ void ClientModel::createClientList(bool partialReset)
     createClientList(tabBox->currentDesktop(), partialReset);
 }
 
-void ClientModel::createFocusChainClientList(int desktop,
-    const QSharedPointer<TabBoxClient> &start, TabBoxClientList &stickyClients)
+TabBoxClientList ClientModel::createFocusChainClientList(int desktop,
+                                                         const QSharedPointer<TabBoxClient> &start,
+                                                         TabBoxClientList &stickyClients) const
 {
     auto c = start;
     if (!tabBox->isInFocusChain(c.data())) {
@@ -163,23 +164,29 @@ void ClientModel::createFocusChainClientList(int desktop,
         }
     }
     auto stop = c;
+
+    TabBoxClientList newClientList;
     do {
         QSharedPointer<TabBoxClient> add = tabBox->clientToAddToList(c.data(), desktop);
         if (!add.isNull()) {
-            m_clientList += add;
+            newClientList += add;
             if (add.data()->isFirstInTabBox()) {
                 stickyClients << add;
             }
         }
         c = tabBox->nextClientFocusChain(c.data());
     } while (c && c != stop);
+
+    return newClientList;
 }
 
-void ClientModel::createStackingOrderClientList(int desktop,
-    const QSharedPointer<TabBoxClient> &start, TabBoxClientList &stickyClients)
+TabBoxClientList ClientModel::createStackingOrderClientList(int desktop,
+                                                            const QSharedPointer<TabBoxClient> &start,
+                                                            TabBoxClientList &stickyClients) const
 {
     // TODO: needs improvement
     const TabBoxClientList stacking = tabBox->stackingOrder();
+    TabBoxClientList newClientList;
     auto c = stacking.first().toStrongRef();
     auto stop = c;
     int index = 0;
@@ -187,10 +194,10 @@ void ClientModel::createStackingOrderClientList(int desktop,
         QSharedPointer<TabBoxClient> add = tabBox->clientToAddToList(c.data(), desktop);
         if (!add.isNull()) {
             if (start == add.data()) {
-                m_clientList.removeAll(add);
-                m_clientList.prepend(add);
+                newClientList.removeAll(add);
+                newClientList.prepend(add);
             } else {
-                m_clientList += add;
+                newClientList += add;
             }
             if (add.data()->isFirstInTabBox()) {
                 stickyClients << add;
@@ -206,6 +213,8 @@ void ClientModel::createStackingOrderClientList(int desktop,
             break;
         }
     }
+
+    return newClientList;
 }
 
 void ClientModel::createClientList(int desktop, bool partialReset)
@@ -219,39 +228,46 @@ void ClientModel::createClientList(int desktop, bool partialReset)
         }
     }
 
-    beginResetModel();
-    m_clientList.clear();
+    TabBoxClientList newClientList;
     TabBoxClientList stickyClients;
 
     switch (tabBox->config().clientSwitchingMode()) {
     case TabBoxConfig::FocusChainSwitching: {
-        createFocusChainClientList(desktop, start, stickyClients);
+        newClientList = createFocusChainClientList(desktop, start, stickyClients);
         break;
     }
     case TabBoxConfig::StackingOrderSwitching: {
-        createStackingOrderClientList(desktop, start, stickyClients);
+        newClientList = createStackingOrderClientList(desktop, start, stickyClients);
         break;
     }
     }
 
     if (tabBox->config().orderMinimizedMode() == TabBoxConfig::GroupByMinimized) {
         // Put all non-minimized included clients first.
-        std::stable_partition(m_clientList.begin(), m_clientList.end(), [](const auto &client) {
+        std::stable_partition(newClientList.begin(), newClientList.end(), [](const auto &client) {
             return !client.toStrongRef()->isMinimized();
         });
     }
 
     for (const QWeakPointer<TabBoxClient> &c : std::as_const(stickyClients)) {
-        m_clientList.removeAll(c);
-        m_clientList.prepend(c);
+        newClientList.removeAll(c);
+        newClientList.prepend(c);
     }
+
     if (tabBox->config().clientApplicationsMode() != TabBoxConfig::AllWindowsCurrentApplication
         && (tabBox->config().showDesktopMode() == TabBoxConfig::ShowDesktopClient || m_clientList.isEmpty())) {
         QWeakPointer<TabBoxClient> desktopClient = tabBox->desktopClient();
         if (!desktopClient.isNull()) {
-            m_clientList.append(desktopClient);
+            newClientList.append(desktopClient);
         }
     }
+
+    if (m_clientList == newClientList) {
+        return;
+    }
+
+    beginResetModel();
+    m_clientList = newClientList;
     endResetModel();
 }
 
diff --git a/src/tabbox/clientmodel.h b/src/tabbox/clientmodel.h
index e1e0dbe1b4..6f1336ead6 100644
--- a/src/tabbox/clientmodel.h
+++ b/src/tabbox/clientmodel.h
@@ -93,10 +93,10 @@ public Q_SLOTS:
     void activate(int index);
 
 private:
-    void createFocusChainClientList(int desktop, const QSharedPointer<TabBoxClient> &start,
-        TabBoxClientList &stickyClients);
-    void createStackingOrderClientList(int desktop, const QSharedPointer<TabBoxClient> &start,
-        TabBoxClientList &stickyClients);
+    TabBoxClientList createFocusChainClientList(int desktop, const QSharedPointer<TabBoxClient> &start,
+                                                TabBoxClientList &stickyClients) const;
+    TabBoxClientList createStackingOrderClientList(int desktop, const QSharedPointer<TabBoxClient> &start,
+                                                   TabBoxClientList &stickyClients) const;
 
     TabBoxClientList m_clientList;
 };