Use slice method where applicable

These code segments already have its boundary checked and can thus be faster.

PR #22411.

src/gui/addnewtorrentdialog.cpp

@@ -122,7 +122,7 @@ namespace
         fsPathEdit->setCurrentIndex(existingIndex);
     }
 
-    void updatePathHistory(const QString &settingsKey, const Path &path, const int maxLength)
+    void updatePathHistory(const QString &settingsKey, const Path &path, const qsizetype maxLength)
     {
         // Add last used save path to the front of history
 
@@ -134,7 +134,10 @@ namespace
         else
             pathList.prepend(path.toString());
 
-        settings()->storeValue(settingsKey, QStringList(pathList.mid(0, maxLength)));
+        if (pathList.size() > maxLength)
+            pathList.resize(maxLength);
+
+        settings()->storeValue(settingsKey, pathList);
     }
 }
 
@@ -375,8 +378,7 @@ AddNewTorrentDialog::AddNewTorrentDialog(const BitTorrent::TorrentDescriptor &to
     connect(Preferences::instance(), &Preferences::changed, []
     {
         const int length = Preferences::instance()->addNewTorrentDialogSavePathHistoryLength();
-        settings()->storeValue(KEY_SAVEPATHHISTORY
-                , QStringList(settings()->loadValue<QStringList>(KEY_SAVEPATHHISTORY).mid(0, length)));
+        settings()->storeValue(KEY_SAVEPATHHISTORY, settings()->loadValue<QStringList>(KEY_SAVEPATHHISTORY).mid(0, length));
     });
 
     setCurrentContext(std::make_shared<Context>(Context {torrentDescr, inParams}));

src/gui/fspathedit.cpp

@@ -234,14 +234,14 @@ void FileSystemPathEdit::setFileNameFilter(const QString &val)
     const int closeBracePos = val.indexOf(u')', (openBracePos + 1));
     if ((openBracePos > 0) && (closeBracePos > 0) && (closeBracePos > openBracePos + 2))
     {
-        QString filterString = val.mid(openBracePos + 1, closeBracePos - openBracePos - 1);
+        const QString filterString = val.sliced((openBracePos + 1), (closeBracePos - openBracePos - 1));
         if (filterString == u"*")
         {        // no filters
             d->m_editor->setFilenameFilters({});
         }
         else
         {
-            QStringList filters = filterString.split(u' ', Qt::SkipEmptyParts);
+            const QStringList filters = filterString.split(u' ', Qt::SkipEmptyParts);
             d->m_editor->setFilenameFilters(filters);
         }
     }

src/gui/optionsdialog.cpp

@@ -1859,10 +1859,10 @@ void OptionsDialog::setLocale(const QString &localeStr)
     if (index < 0)
     {
         //Attempt to find a language match without a country
-        int pos = name.indexOf(u'_');
+        const int pos = name.indexOf(u'_');
         if (pos > -1)
         {
-            QString lang = name.left(pos);
+            const QString lang = name.first(pos);
             index = m_ui->comboLanguage->findData(lang, Qt::UserRole);
         }
     }

src/gui/rss/rsswidget.cpp

@@ -82,7 +82,13 @@ namespace
 
             QString relativePath = match.captured(6);
             if (relativePath.startsWith(u'/'))
-                relativePath = relativePath.mid(1);
+            {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+                relativePath.slice(1);
+#else
+                relativePath.remove(0, 1);
+#endif
+            }
 
             const QString absoluteUrl = !host.isEmpty()
                     ? QString(defaultScheme + u':' + host) : (normalizedBaseUrl + relativePath);

src/gui/search/searchsortmodel.cpp

@@ -46,7 +46,7 @@ void SearchSortModel::setNameFilter(const QString &searchTerm)
 {
     m_searchTerm = searchTerm;
     if ((searchTerm.length() > 2) && searchTerm.startsWith(u'"') && searchTerm.endsWith(u'"'))
-        m_searchTermWords = QStringList(m_searchTerm.mid(1, m_searchTerm.length() - 2));
+        m_searchTermWords = QStringList(m_searchTerm.sliced(1, (m_searchTerm.length() - 2)));
     else
         m_searchTermWords = searchTerm.split(u' ', Qt::SkipEmptyParts);
 }

src/gui/search/searchwidget.cpp

@@ -675,7 +675,7 @@ void SearchWidget::loadHistory()
         }
 
         if (history.size() > m_historyLength)
-            history = history.mid(history.size() - m_historyLength);
+            history.remove(0, (history.size() - m_historyLength));
 
         m_searchPatternCompleterModel->setStringList(history);
     });

src/gui/transferlistfilters/categoryfiltermodel.cpp

@@ -174,9 +174,9 @@ namespace
 {
     QString shortName(const QString &fullName)
     {
-        int pos = fullName.lastIndexOf(u'/');
+        const int pos = fullName.lastIndexOf(u'/');
         if (pos >= 0)
-            return fullName.mid(pos + 1);
+            return fullName.sliced(pos + 1);
         return fullName;
     }
 }

src/gui/transferlistfilters/trackersfilterwidget.cpp

@@ -555,7 +555,7 @@ void TrackersFilterWidget::handleFavicoDownloadFinished(const Net::DownloadResul
     {
         if (result.url.endsWith(u".ico", Qt::CaseInsensitive))
         {
-            const QString faviconURL = result.url.left(result.url.size() - 4) + u".png";
+            const QString faviconURL = QStringView(result.url).chopped(4) + u".png";
             for (const auto &trackerHost : trackerHosts)
             {
                 if (m_trackers.contains(trackerHost))