Gives a warning when there are unsaved changes when opening a file or closing the window.

mainwindow.cpp

@@ -6,6 +6,7 @@
 #include "sqlhighlighter.h"
 #include <QStandardPaths>
 #include <QFileDialog>
+#include <QMessageBox>
 #include <QTextDocumentFragment>
 #include <QTextStream>
 #include <QTextTable>
@@ -14,6 +15,7 @@
 #include "json/json.h"
 #include "explaintreemodelitem.h"
 #include <algorithm>
+#include <QCloseEvent>
 
 //#include <thread>
 
@@ -121,6 +123,8 @@ MainWindow::MainWindow(QWidget *parent)
 			QueueTask([this, details]() { receiveNotice(details); });
 		});
 
+	connect(ui->queryEdit, &QPlainTextEdit::textChanged, this, &MainWindow::queryTextChanged);
+
 	m_timeElapsedLabel = new QLabel(this);
 	statusBar()->addPermanentWidget(m_timeElapsedLabel);
 }
@@ -420,9 +424,24 @@ void MainWindow::endTimer()
 	}
 }
 
+bool MainWindow::continueWithoutSaving()
+{
+	QMessageBox msgBox;
+	msgBox.setText("The document has been modified.");
+	msgBox.setInformativeText("The current query has unsaved changes, do you want to continue without saving those changes?");
+	msgBox.setStandardButtons(QMessageBox::Yes | QMessageBox::No);
+	msgBox.setDefaultButton(QMessageBox::No);
+	int ret = msgBox.exec();
+	return ret == QMessageBox::Yes;
+}
+
 void MainWindow::on_actionLoad_SQL_triggered()
 {
 	//
+	if (m_queryTextChanged && !continueWithoutSaving()) {
+		return;
+	}
+
 	QString home_dir = QStandardPaths::locate(QStandardPaths::HomeLocation, "", QStandardPaths::LocateDirectory);
 	QString file_name = QFileDialog::getOpenFileName(this,
 		tr("Open sql query"), home_dir, tr("SQL files (*.sql *.txt)"));
@@ -435,6 +454,7 @@ void MainWindow::on_actionLoad_SQL_triggered()
 				QString line = stream.readLine();
 				ui->queryEdit->appendPlainText(line);
 			}
+			m_queryTextChanged = false;
 		}
 
 
@@ -452,6 +472,7 @@ void MainWindow::on_actionSave_SQL_triggered()
 			QTextStream stream(&file);
 			QString text = ui->queryEdit->toPlainText();
 			stream << text;
+			m_queryTextChanged = false;
 		}
 	}
 }
@@ -519,3 +540,18 @@ void MainWindow::on_actionCancel_triggered()
 {
 	cancel_query();
 }
+
+void MainWindow::queryTextChanged()
+{
+	m_queryTextChanged = true;
+}
+
+void MainWindow::closeEvent(QCloseEvent *event)
+{
+	if (!m_queryTextChanged  || continueWithoutSaving()) {
+		event->accept();
+	}
+	else {
+		event->ignore();
+	}
+}