Set Maximum Tab Width for folders to Tab bar

There is no limit to the width of tabs with the tab bar of the main window. If the directory name is too long, tabs can take up a lot of space and can lead to inconsistent tab widths.

To alleviate this, set a maximum tab bar text width of 40 characters for each folder.

BUG: 420870

src/dolphintabwidget.cpp

@@ -15,6 +15,7 @@
 #include <KIO/CommandLauncherJob>
 #include <KLocalizedString>
 #include <KShell>
+#include <KStringHandler>
 #include <kio/global.h>
 
 #include <QApplication>
@@ -507,7 +508,7 @@ QString DolphinTabWidget::tabName(DolphinTabPage *tabPage) const
 
     // Make sure that a '&' inside the directory name is displayed correctly
     // and not misinterpreted as a keyboard shortcut in QTabBar::setTabText()
-    return name.replace('&', QLatin1String("&&"));
+    return KStringHandler::rsqueeze(name.replace('&', QLatin1String("&&")), 40 /* default maximum visible folder name visible */);
 }
 
 DolphinViewContainer *DolphinTabWidget::viewContainerAt(DolphinTabWidget::ViewIndex viewIndex) const