PrintView improvements (#250)

- Allow printer selection directly from PrintView
- Print button bypasses the system print dialog, since label printing is quite different from typical printing tasks
- Separate button to optionally use system print dialog, if needed

glabels/PrinterMonitor.h

@@ -0,0 +1,87 @@
+/*  PrinterMonitor.h
+ *
+ *  Copyright (C) 2025  Jaye Evins <evins@snaught.com>
+ *
+ *  This file is part of gLabels-qt.
+ *
+ *  gLabels-qt 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 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  gLabels-qt 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 gLabels-qt.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef PrinterMonitor_h
+#define PrinterMonitor_h
+
+
+#include <QObject>
+#include <QStringList>
+#include <QTimer>
+
+#include <memory>
+
+
+namespace glabels
+{
+
+	///
+	/// Printer Monitor
+	///
+	class PrinterMonitor : public QObject
+	{
+		Q_OBJECT
+
+		/////////////////////////////////
+		// Life Cycle
+		/////////////////////////////////
+	private:
+		PrinterMonitor();
+
+	public:
+		static PrinterMonitor* instance();
+
+
+		/////////////////////////////////
+		// Public methods
+		/////////////////////////////////
+	public:
+		const QStringList& availablePrinters() const;
+
+
+		/////////////////////////////////
+		// Slots
+		/////////////////////////////////
+	private slots:
+		void onTimerTimeout();
+			
+
+		/////////////////////////////////
+		// Signals
+		/////////////////////////////////
+	signals:
+		void availablePrintersChanged( const QStringList& availablePrinters );
+
+
+		/////////////////////////////////
+		// Private Members
+		/////////////////////////////////
+	private:
+		static std::unique_ptr<PrinterMonitor> mInstance;
+
+		std::unique_ptr<QTimer> mTimer;
+		QStringList mCurrentAvailablePrinters;
+
+	};
+
+}
+
+
+#endif // PrinterMonitor_h