From e7e576ad29a14a157521ca0fab71baffcba9d0c1 Mon Sep 17 00:00:00 2001
From: Nodir Temirkhodjaev <nodir.temir@gmail.com>
Date: Sun, 15 Apr 2018 11:19:31 +0500
Subject: [PATCH] UI: Improve startup checks.

---
 src/ui/main.cpp        | 17 ++++++++++++++---
 src/ui/util/osutil.cpp |  3 ++-
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/ui/main.cpp b/src/ui/main.cpp
index eeda0dfc..c07ae81a 100644
--- a/src/ui/main.cpp
+++ b/src/ui/main.cpp
@@ -1,4 +1,5 @@
 #include <QApplication>
+#include <QMessageBox>
 
 #include "../common/version.h"
 #include "driver/drivermanager.h"
@@ -7,6 +8,9 @@
 #include "fortsettings.h"
 #include "util/osutil.h"
 
+#define FORT_ERROR_INSTANCE 1
+#define FORT_ERROR_DEVICE   2
+
 int main(int argc, char *argv[])
 {
     QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
@@ -28,13 +32,20 @@ int main(int argc, char *argv[])
     }
 
     // To check running instance
-    OsUtil::createGlobalMutex(APP_NAME);
+    if (!OsUtil::createGlobalMutex(APP_NAME)) {
+        QMessageBox::critical(nullptr, QString(),
+                              "Application is already running!");
+        return FORT_ERROR_INSTANCE;
+    }
 
     FortManager fortManager(&fortSettings);
 
     // Error: Cannot open the driver device
-    if (!fortManager.driverManager()->isDeviceOpened())
-        return 1;
+    if (!fortManager.driverManager()->isDeviceOpened()) {
+        QMessageBox::critical(nullptr, QString(),
+                              "Cannot open the driver device!");
+        return FORT_ERROR_DEVICE;
+    }
 
     fortManager.showTrayIcon();
 
diff --git a/src/ui/util/osutil.cpp b/src/ui/util/osutil.cpp
index 32e88e73..e317384f 100644
--- a/src/ui/util/osutil.cpp
+++ b/src/ui/util/osutil.cpp
@@ -18,7 +18,8 @@ QString OsUtil::pidToPath(quint32 pid, bool isKernelPath)
 
 bool OsUtil::createGlobalMutex(const char *name)
 {
-    return !CreateMutexA(nullptr, FALSE, name);
+    return CreateMutexA(nullptr, FALSE, name)
+            && GetLastError() != ERROR_ALREADY_EXISTS;
 }
 
 quint32 OsUtil::lastErrorCode()