Merge pull request #54 from robotpy/fix-crash

Wrap VideoListener to hold a reference to the callback

src/_cscore.cpp

@@ -19,6 +19,23 @@ using namespace cs;
 typedef py::call_guard<py::gil_scoped_release> release_gil;
 
 
+
+// Wrapper for VideoListener to prevent crashes on shutdown
+class VideoListenerWrapper : public VideoListener {
+public:
+    VideoListenerWrapper(std::function<void(const VideoEvent&)> callback, int eventMask, bool immediateNotify) :
+        VideoListener(callback, eventMask, immediateNotify),
+        m_callback(callback)
+    {}
+
+    virtual ~VideoListenerWrapper() {}
+
+private:
+    // need a reference to this callback otherwise cscore crashes on exit
+    std::function<void(const VideoEvent&)> m_callback;
+};
+
+
 PYBIND11_MODULE(_cscore, m) {
 
     NDArrayConverter::init_numpy();
@@ -582,7 +599,7 @@ PYBIND11_MODULE(_cscore, m) {
       .def("getProperty", &VideoEvent::GetProperty);
 
 
-    py::class_<VideoListener> videolistener(m, "VideoListener");
+    py::class_<VideoListenerWrapper> videolistener(m, "VideoListener");
     videolistener.doc() = 
         "An event listener.  This calls back to a desigated callback function when\n"
         "an event matching the specified mask is generated by the library.";