Add a save option to discard MIDI connections (#5021)

* Song: add isSavingProject.
* VersionedSaveDialog: Add support for a custom option dialog.
* AutomatableModel: Support the discardMIDIConnections save option.
* InstrumentTrack: Support the discardMIDIConnections save option.
* SaveOptions: Show the save option dialog on "save as".

include/Song.h

@@ -65,6 +65,17 @@ public:
 		Mode_Count
 	} ;
 
+	struct SaveOptions {
+		/**
+		 * Should we discard MIDI ControllerConnections from project files?
+		 */
+		BoolModel discardMIDIConnections{false};
+
+		void setDefaultOptions() {
+			discardMIDIConnections.setValue(false);
+		}
+	};
+
 	void clearErrors();
 	void collectError( const QString error );
 	bool hasErrors();
@@ -322,6 +333,11 @@ public:
 	void exportProjectMidi(QString const & exportFileName) const;
 
 	inline void setLoadOnLauch(bool value) { m_loadOnLaunch = value; }
+	SaveOptions &getSaveOptions() {
+		return m_saveOptions;
+	}
+
+	bool isSavingProject() const;
 
 public slots:
 	void playSong();
@@ -419,9 +435,12 @@ private:
 	volatile bool m_playing;
 	volatile bool m_paused;
 
+	bool m_savingProject;
 	bool m_loadingProject;
 	bool m_isCancelled;
 
+	SaveOptions m_saveOptions;
+
 	QStringList m_errors;
 
 	PlayModes m_playMode;

include/VersionedSaveDialog.h

@@ -29,15 +29,25 @@
 #define VERSIONEDSAVEDIALOG_H
 
 #include "FileDialog.h"
+#include "Song.h"
 
 class QLineEdit;
+class LedCheckBox;
 
+class SaveOptionsWidget : public QWidget {
+public:
+	SaveOptionsWidget(Song::SaveOptions &saveOptions);
+
+private:
+	LedCheckBox *m_discardMIDIConnectionsCheckbox;
+};
 
 class VersionedSaveDialog : public FileDialog
 {
 	Q_OBJECT
 public:
 	explicit VersionedSaveDialog( QWidget *parent = 0,
+								  QWidget *saveOptionsWidget = nullptr,
 								  const QString &caption = QString(),
 								  const QString &directory = QString(),
 								  const QString &filter = QString() );