Fix 'Filter Sidebar' size restored incorrectly

And with a bit of code clean up.
Closes #17756.

src/gui/mainwindow.cpp

@@ -219,8 +219,8 @@ MainWindow::MainWindow(IGUIApplication *app, const State initialState)
         tr("Transfers"));
 
     connect(m_searchFilter, &LineEdit::textChanged, m_transferListWidget, &TransferListWidget::applyNameFilter);
-    connect(hSplitter, &QSplitter::splitterMoved, this, &MainWindow::writeSettings);
-    connect(m_splitter, &QSplitter::splitterMoved, this, &MainWindow::writeSplitterSettings);
+    connect(hSplitter, &QSplitter::splitterMoved, this, &MainWindow::saveSettings);
+    connect(m_splitter, &QSplitter::splitterMoved, this, &MainWindow::saveSplitterSettings);
     connect(BitTorrent::Session::instance(), &BitTorrent::Session::trackersChanged, m_propertiesWidget, &PropertiesWidget::loadTrackers);
 
 #ifdef Q_OS_MACOS
@@ -357,7 +357,7 @@ MainWindow::MainWindow(IGUIApplication *app, const State initialState)
         m_ui->actionAutoShutdownDisabled->setChecked(true);
 
     // Load Window state and sizes
-    readSettings();
+    loadSettings();
 
     app->desktopIntegration()->setMenu(createDesktopIntegrationMenu());
 #ifndef Q_OS_MACOS
@@ -739,23 +739,26 @@ void MainWindow::tabChanged(int newTab)
     }
 }
 
-void MainWindow::writeSettings()
+void MainWindow::saveSettings() const
 {
-    Preferences *const pref = Preferences::instance();
+    auto *pref = Preferences::instance();
     pref->setMainGeometry(saveGeometry());
     m_propertiesWidget->saveSettings();
 }
 
-void MainWindow::writeSplitterSettings()
+void MainWindow::saveSplitterSettings() const
 {
-    Q_ASSERT(m_splitter->widget(0) == m_transferListFiltersWidget);
-    Preferences *const pref = Preferences::instance();
+    if (!m_transferListFiltersWidget)
+        return;
+
+    auto *pref = Preferences::instance();
     pref->setFiltersSidebarWidth(m_splitter->sizes()[0]);
 }
 
 void MainWindow::cleanup()
 {
-    writeSettings();
+    saveSettings();
+    saveSplitterSettings();
 
     // delete RSSWidget explicitly to avoid crash in
     // handleRSSUnreadCountUpdated() at application shutdown
@@ -775,13 +778,16 @@ void MainWindow::cleanup()
         delete w;
 }
 
-void MainWindow::readSettings()
+void MainWindow::loadSettings()
+{
+    const auto *pref = Preferences::instance();
+
+    if (const QByteArray mainGeo = pref->getMainGeometry();
+        !mainGeo.isEmpty() && restoreGeometry(mainGeo))
     {
-    const Preferences *const pref = Preferences::instance();
-    const QByteArray mainGeo = pref->getMainGeometry();
-    if (!mainGeo.isEmpty() && restoreGeometry(mainGeo))
         m_posInitialized = true;
     }
+}
 
 void MainWindow::desktopNotificationClicked()
 {
@@ -1377,27 +1383,27 @@ void MainWindow::showStatusBar(bool show)
 
 void MainWindow::showFiltersSidebar(const bool show)
 {
-    Preferences *const pref = Preferences::instance();
-
     if (show && !m_transferListFiltersWidget)
     {
-        const int width = pref->getFiltersSidebarWidth();
         m_transferListFiltersWidget = new TransferListFiltersWidget(m_splitter, m_transferListWidget, isDownloadTrackerFavicon());
-        m_splitter->insertWidget(0, m_transferListFiltersWidget);
-        m_splitter->setCollapsible(0, true);
-        m_splitter->setSizes({width, (m_splitter->width() - width)});
-
         connect(BitTorrent::Session::instance(), &BitTorrent::Session::trackersAdded, m_transferListFiltersWidget, &TransferListFiltersWidget::addTrackers);
         connect(BitTorrent::Session::instance(), &BitTorrent::Session::trackersRemoved, m_transferListFiltersWidget, &TransferListFiltersWidget::removeTrackers);
         connect(BitTorrent::Session::instance(), &BitTorrent::Session::trackersChanged, m_transferListFiltersWidget, &TransferListFiltersWidget::refreshTrackers);
         connect(BitTorrent::Session::instance(), &BitTorrent::Session::trackerlessStateChanged, m_transferListFiltersWidget, &TransferListFiltersWidget::changeTrackerless);
         connect(BitTorrent::Session::instance(), &BitTorrent::Session::trackerEntriesUpdated, m_transferListFiltersWidget, &TransferListFiltersWidget::trackerEntriesUpdated);
+
+        m_splitter->insertWidget(0, m_transferListFiltersWidget);
+        m_splitter->setCollapsible(0, true);
+        // From https://doc.qt.io/qt-5/qsplitter.html#setSizes:
+        // Instead, any additional/missing space is distributed amongst the widgets
+        // according to the relative weight of the sizes.
+        m_splitter->setStretchFactor(0, 0);
+        m_splitter->setStretchFactor(1, 1);
+        m_splitter->setSizes({Preferences::instance()->getFiltersSidebarWidth()});
     }
     else if (!show && m_transferListFiltersWidget)
     {
-        Q_ASSERT(m_splitter->widget(0) == m_transferListFiltersWidget);
-
-        pref->setFiltersSidebarWidth(m_splitter->sizes()[0]);
+        saveSplitterSettings();
         delete m_transferListFiltersWidget;
         m_transferListFiltersWidget = nullptr;
     }

src/gui/mainwindow.h

@@ -110,9 +110,9 @@ public:
 private slots:
     void showFilterContextMenu();
     void desktopNotificationClicked();
-    void writeSettings();
-    void writeSplitterSettings();
-    void readSettings();
+    void saveSettings() const;
+    void loadSettings();
+    void saveSplitterSettings() const;
     void tabChanged(int newTab);
     bool defineUILockPassword();
     void clearUILockPassword();

src/gui/transferlistfilterswidget.h

@@ -44,6 +44,8 @@
 class QCheckBox;
 class QResizeEvent;
 
+class CategoryFilterWidget;
+class TagFilterWidget;
 class TransferListWidget;
 
 namespace Net
@@ -163,9 +165,6 @@ private:
     bool m_downloadTrackerFavicon;
 };
 
-class CategoryFilterWidget;
-class TagFilterWidget;
-
 class TransferListFiltersWidget final : public QFrame
 {
     Q_OBJECT