FileBrowser: "Open containing folder" automatically selects file in the OS's file manager (#7700)

Introduces a new class FileRevealer to manage file selection across different platforms (Windows, macOS, Linux, and other *nix operating systems with xdg). Includes methods to open and select files or directories using the default file manager on the respective platform.

---------

Co-authored-by: Tres Finocchiaro <tres.finocchiaro@gmail.com>
Co-authored-by: Hyunjin Song <tteu.ingog@gmail.com>
Co-authored-by: Sotonye Atemie <sakertooth@gmail.com>
Co-authored-by: Dalton Messmer <messmer.dalton@gmail.com>

include/FileBrowser.h

@@ -195,8 +195,6 @@ private slots:
 	bool openInNewSampleTrack( lmms::gui::FileItem* item );
 	void sendToActiveInstrumentTrack( lmms::gui::FileItem* item );
 	void updateDirectory( QTreeWidgetItem * item );
-	void openContainingFolder( lmms::gui::FileItem* item );
-
 } ;
 
 

include/FileRevealer.h

@@ -0,0 +1,77 @@
+/*
+ * FileRevealer.h - include file for FileRevealer
+ *
+ * Copyright (c) 2025 Andrew Wiltshire <aw1lt / at/ proton/ dot/me >
+ *
+ * This file is part of LMMS - https://lmms.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef LMMS_FILE_REVEALER_H
+#define LMMS_FILE_REVEALER_H
+
+#include <QFileInfo>
+
+namespace lmms {
+
+/**
+ * @class FileRevealer
+ * @brief A utility class for revealing files and directories in the system's file manager.
+ */
+class FileRevealer
+{
+public:
+	/**
+	 * @brief Retrieves the default file manager for the current platform.
+	 * @return The name or command of the default file manager.
+	 */
+	static const QString& getDefaultFileManager();
+
+	/**
+	 * @brief Opens the directory containing the specified file or folder in the file manager.
+	 * @param item The QFileInfo object representing the file or folder.
+	 */
+	static void openDir(const QFileInfo item);
+
+	/**
+	 * @brief Checks whether the file manager supports selecting a specific file.
+	 * @return True if selection is supported, otherwise false.
+	 */
+	static const QStringList& getSelectCommand();
+
+	/**
+	 * @brief Opens the file manager and selects the specified file if supported.
+	 * @param item The QFileInfo object representing the file to reveal.
+	 */
+	static void reveal(const QFileInfo item);
+
+private:
+	static bool s_canSelect;
+
+protected:
+	/**
+	 * @brief Determines if the given command supports the argument
+	 * @param command The name of the file manager to check.
+	 * @param arg The command line argument to parse for
+	 * @return True if the file command the argument, otherwise false.
+	 */
+	static bool supportsArg(const QString& command, const QString& arg);
+};
+
+} // namespace lmms
+#endif // LMMS_FILE_REVEALER_H