Add "Clear Recent files list" item (#22638)

* Add "Clear Recent files" item

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Chris Hennes <chennes@pioneerlibrarysystem.org>

src/Gui/Action.cpp

@@ -858,6 +858,32 @@ RecentFilesAction::RecentFilesAction ( Command* pcCmd, QObject * parent )
 {
     _pimpl = std::make_unique<Private>(this, "User parameter:BaseApp/Preferences/RecentFiles");
     restore();
+
+    sep.setSeparator(true);
+    sep.setToolTip({});
+    this->groupAction()->addAction(&sep);
+
+    //: Empties the list of recent files
+    clearRecentFilesListAction.setText(tr("Clear Recent Files"));
+    clearRecentFilesListAction.setToolTip({});
+    this->groupAction()->addAction(&clearRecentFilesListAction);
+
+    auto clearFun = [this, hGrp = _pimpl->handle](){
+        const size_t recentFilesListSize = hGrp->GetASCIIs("MRU").size();
+        for (size_t i = 0; i < recentFilesListSize; i++)
+        {
+            const QByteArray key = QStringLiteral("MRU%1").arg(i).toLocal8Bit();
+            hGrp->SetASCII(key.data(), "");
+        }
+        restore();
+        clearRecentFilesListAction.setEnabled(false);
+    };
+
+    connect(&clearRecentFilesListAction, &QAction::triggered,
+            this, clearFun);
+
+    connect(&clearRecentFilesListAction, &QAction::triggered,
+            this, &RecentFilesAction::recentFilesListModified);
 }
 
 RecentFilesAction::~RecentFilesAction()
@@ -878,6 +904,10 @@ void RecentFilesAction::appendFile(const QString& filename)
     save();
 
     _pimpl->trySaveUserParameter();
+
+    clearRecentFilesListAction.setEnabled(true);
+
+    Q_EMIT recentFilesListModified();
 }
 
 static QString numberToLabel(int number) {
@@ -921,6 +951,9 @@ void RecentFilesAction::setFiles(const QStringList& files)
     // if less file names than actions
     numRecentFiles = std::min<int>(numRecentFiles, this->visibleItems);
     for (int index = numRecentFiles; index < recentFiles.count(); index++) {
+        if (recentFiles[index] == &sep || recentFiles[index] == &clearRecentFilesListAction) {
+            continue;
+        }
         recentFiles[index]->setVisible(false);
         recentFiles[index]->setText(QString());
         recentFiles[index]->setToolTip(QString());