Stupid proof Linux serial port use

src/QGCApplication.cc

@@ -188,6 +188,45 @@ QGCApplication::QGCApplication(int &argc, char* argv[], bool unitTesting)
     setAttribute(Qt::AA_DontCreateNativeWidgetSiblings);
 #endif
 
+#ifdef Q_OS_LINUX
+#ifndef __mobile__
+    if (getuid() == 0) {
+        QMessageBox msgBox;
+        msgBox.setInformativeText("You are runnning QGroundControl as root. "
+                                  "You should not do this since it will cause other issues with QGroundControl. "
+                                  "QGroundControl will now exit. "
+                                  "If you are having serial port issues, execute the following commands to fix most serial port issues:\n"
+                                  "sudo usermod -a -G dialout $USER\n"
+                                  "sudo apt-get remove modemmanager");
+        msgBox.setStandardButtons(QMessageBox::Ok);
+        msgBox.setDefaultButton(QMessageBox::Ok);
+        msgBox.exec();
+        _exit(0);
+    }
+
+    // Determine if we have the correct permissions to access USB serial devices
+    QFile permFile("/etc/group");
+    if(permFile.open(QIODevice::ReadOnly)) {
+        while(!permFile.atEnd()) {
+            QString line = permFile.readLine();
+            if (line.contains("dialout") && !line.contains(getenv("USER"))) {
+                QMessageBox msgBox;
+                msgBox.setInformativeText("The current user does not have the correct permissions to access serial devices. "
+                                          "You should also remove modemmanager since it also interferes. "
+                                          "Execute the following commands to fix these issues:\n"
+                                          "sudo usermod -a -G dialout $USER\n"
+                                          "sudo apt-get remove modemmanager");
+                msgBox.setStandardButtons(QMessageBox::Ok);
+                msgBox.setDefaultButton(QMessageBox::Ok);
+                msgBox.exec();
+                break;
+            }
+        }
+        permFile.close();
+    }
+#endif
+#endif
+
     // Parse command line options
 
     bool fClearSettingsOptions = false; // Clear stored settings