potentially fix hang despite volatile

gistfile1.txt

diff --git a/facetracknoir/facetracknoir.cpp b/facetracknoir/facetracknoir.cpp
index b83f59d..d93f213 100644
--- a/facetracknoir/facetracknoir.cpp
+++ b/facetracknoir/facetracknoir.cpp
@@ -360,7 +360,6 @@ void FaceTrackNoIR::startTracker( ) {
 #endif
 
     if (tracker) {
-        tracker->wait();
         delete tracker;
     }
 
@@ -418,8 +417,6 @@ void FaceTrackNoIR::stopTracker( ) {
         pFilterDialog->unregisterFilter();
 
     if ( tracker ) {
-        tracker->should_quit = true;
-        tracker->wait();
 		delete tracker;
 		tracker = 0;
         if (Libraries) {
diff --git a/facetracknoir/tracker.cpp b/facetracknoir/tracker.cpp
index fa1cdee..5776264 100644
--- a/facetracknoir/tracker.cpp
+++ b/facetracknoir/tracker.cpp
@@ -31,6 +31,12 @@ Tracker::Tracker(FaceTrackNoIR *parent , main_settings& s) :
 {
 }
 
+Tracker::~Tracker()
+{
+    should_quit = true;
+    wait();
+}
+
 static void get_curve(double pos, double& out, THeadPoseDOF& axis) {
     bool altp = (pos < 0) && axis.opts.altp;
     if (altp) {
diff --git a/facetracknoir/tracker.h b/facetracknoir/tracker.h
index 7ebece0..a33d8e0 100644
--- a/facetracknoir/tracker.h
+++ b/facetracknoir/tracker.h
@@ -51,28 +51,29 @@ public:
     axis_opts& opts;
 };
 
-class Tracker : public QThread {
+class Tracker : protected QThread {
 	Q_OBJECT
 
 private:
     FaceTrackNoIR *mainApp;
     QMutex mtx;
     main_settings& s;
-
+    volatile bool should_quit;
 protected:
 	void run();
 
 public:
     Tracker( FaceTrackNoIR *parent, main_settings& s);
+    ~Tracker();
 
     void getHeadPose(double *data);
     void getOutputHeadPose(double *data);
-
-    volatile bool should_quit;
     volatile bool do_center;
     volatile bool enabled;
     
     T6DOF output_camera;
+
+    void start() { QThread::start(); }
 };
 
 class HeadPoseData {