From 680ad111953d96ac7d842d38564666a0f4286b18 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Patrick=20Jos=C3=A9=20Pereira?= <patrickelectric@gmail.com>
Date: Fri, 17 May 2019 10:28:15 -0300
Subject: [PATCH] main: Returning critical messsage and an error code when QGC
 is already running
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Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>
---
 src/main.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/main.cc b/src/main.cc
index 02be68a..6a79524 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -19,6 +19,7 @@
 #include <QApplication>
 #include <QIcon>
 #include <QSslSocket>
+#include <QMessageBox>
 #include <QProcessEnvironment>
 #include <QHostAddress>
 #include <QUdpSocket>
@@ -222,7 +223,12 @@ int main(int argc, char *argv[])
 #ifndef __mobile__
     RunGuard guard("QGroundControlRunGuardKey");
     if (!guard.tryToRun()) {
-        return 0;
+        // QApplication is necessary to use QMessageBox
+        QApplication errorApp(argc, argv);
+        QMessageBox::critical(nullptr, QObject::tr("Error"),
+            QObject::tr("A second instance of QGroundControl is already running. Please close the other instance and try again.")
+        );
+        return -1;
     }
 #endif