joystick: fix crash on app exit

This fixes a pure virtual method call exception during exit when a joystick
is connected.

The problem was that ~Joystick() waited for the thread to exit, while the
thread called the virtual method _close(). But at this point the destructor
of the derived class (JoystickSDL in my case) was already called.

To resolve the problem a separate stop() method is added that is called
before deleting the object.

src/Joystick/Joystick.cc

@@ -121,10 +121,17 @@ Joystick::Joystick(const QString& name, int axisCount, int buttonCount, int hatC
     connect(_multiVehicleManager, &MultiVehicleManager::activeVehicleChanged, this, &Joystick::_activeVehicleChanged);
 }
 
-Joystick::~Joystick()
+void Joystick::stop()
 {
     _exitThread = true;
     wait();
+}
+
+Joystick::~Joystick()
+{
+    if (!_exitThread) {
+        qWarning() << "Joystick thread still running!";
+    }
     delete[] _rgAxisValues;
     delete[] _rgCalibration;
     delete[] _rgButtonValues;

src/Joystick/Joystick.h

@@ -18,6 +18,7 @@
 #include "QGCLoggingCategory.h"
 #include "Vehicle.h"
 #include "MultiVehicleManager.h"
+#include <atomic>
 
 Q_DECLARE_LOGGING_CATEGORY(JoystickLog)
 Q_DECLARE_LOGGING_CATEGORY(JoystickValuesLog)
@@ -53,7 +54,7 @@ class Joystick : public QThread
 public:
     Joystick(const QString& name, int axisCount, int buttonCount, int hatCount, MultiVehicleManager* multiVehicleManager);
 
-    ~Joystick();
+    virtual ~Joystick();
 
     typedef struct Calibration_t {
         int     min;
@@ -137,6 +138,7 @@ public:
     void setFunctionAxis(AxisFunction_t function, int axis);
     int getFunctionAxis(AxisFunction_t function);
 
+    void stop();
 
 /*
     // Joystick index used by sdl library
@@ -263,7 +265,7 @@ protected:
 
     uint8_t*_rgButtonValues         = nullptr;
 
-    bool    _exitThread             = false;    ///< true: signal thread to exit
+    std::atomic<bool> _exitThread{false};    ///< true: signal thread to exit
     bool    _calibrationMode        = false;
     int*    _rgAxisValues           = nullptr;
     Calibration_t* _rgCalibration   = nullptr;

src/Joystick/JoystickManager.cc

@@ -38,6 +38,7 @@ JoystickManager::~JoystickManager() {
     QMap<QString, Joystick*>::iterator i;
     for (i = _name2JoystickMap.begin(); i != _name2JoystickMap.end(); ++i) {
         qCDebug(JoystickManagerLog) << "Releasing joystick:" << i.key();
+        i.value()->stop();
         delete i.value();
     }
     qDebug() << "Done";