tracker/pt: protect get_n_points()

There's a race here since further accesses to the points array aren't
protected by a mutex in the extractor class.

There's no race in "get_points()" in the extractor since it's only used
in same thread where updates take place.

2 files changed, 2 insertions, 1 deletions

diff --git a/tracker-pt/ftnoir_tracker_pt.h b/tracker-pt/ftnoir_tracker_pt.h
index dff0c30a..5f30c66f 100644
--- a/tracker-pt/ftnoir_tracker_pt.h
+++ b/tracker-pt/ftnoir_tracker_pt.h
@@ -41,7 +41,7 @@ public:
     void data(double* data) override;
 
     Affine pose() { return point_tracker.pose(); }
-    int  get_n_points() { return point_extractor.get_points().size(); }
+    int  get_n_points() { return point_extractor.get_n_points(); }
     bool get_cam_info(CamInfo* info) { QMutexLocker lock(&camera_mtx); return camera.get_info(*info); }
 public slots:
     void apply_settings();
diff --git a/tracker-pt/point_extractor.h b/tracker-pt/point_extractor.h
index 030251ff..8bcc2437 100644
--- a/tracker-pt/point_extractor.h
+++ b/tracker-pt/point_extractor.h
@@ -23,6 +23,7 @@ public:
     // WARNING: returned reference is valid as long as object
     const std::vector<cv::Vec2f> &extract_points(cv::Mat &frame);
     const std::vector<cv::Vec2f>& get_points() { QMutexLocker l(&mtx); return points; }
+    int get_n_points() const { QMutexLocker l(&mtx); return points.size(); }
     PointExtractor();
     
     settings_pt s;