Show UnsavedDocumentsDialog when closing window or quitting application

so user can save and or discard docs more efficiently.

pglab/querytool/UnsavedDocumentsDialog.h

@@ -0,0 +1,48 @@
+#ifndef UNSAVEDDOCUMENTSDIALOG_H
+#define UNSAVEDDOCUMENTSDIALOG_H
+
+#include "SqlDocument.h"
+#include <QDialog>
+#include <QList>
+#include <functional>
+#include <memory>
+
+class QListWidget;
+
+/** Lists modified documents with a checkbox per document. The user picks
+ * whether the checked documents should be saved or discarded.
+ */
+class UnsavedDocumentsDialog : public QDialog {
+	Q_OBJECT
+public:
+	enum class Choice {
+		Cancel,
+		Save,
+		Discard
+	};
+
+	UnsavedDocumentsDialog(const QList<std::shared_ptr<SqlDocument>> &docs, QWidget *parent = nullptr);
+
+	Choice choice() const { return m_choice; }
+	QList<std::shared_ptr<SqlDocument>> checkedDocuments() const;
+	QList<std::shared_ptr<SqlDocument>> uncheckedDocuments() const;
+
+private:
+	QList<std::shared_ptr<SqlDocument>> m_docs;
+	QListWidget *m_list;
+	Choice m_choice = Choice::Cancel;
+};
+
+/** Selects the documents that are closed when every editor for which
+ * isClosing returns true is closed. Only modified documents are returned.
+ */
+QList<std::shared_ptr<SqlDocument>> documentsClosedWith(const QList<std::shared_ptr<SqlDocument>> &docs,
+	const std::function<bool(const QWidget*)> &isClosing);
+
+/** Asks the user what to do with the modified documents. Returns true when
+ * the close may continue, i.e. nothing was cancelled, no save failed and
+ * every listed document was checked.
+ */
+bool confirmClose(QWidget *parent, const QList<std::shared_ptr<SqlDocument>> &docs);
+
+#endif // UNSAVEDDOCUMENTSDIALOG_H