opencv_trail_effect.cpp: use cv::waitKeyEx() instead of cv::waitKey()

In some OpenCV 3 version there was a change of behavior of cv::waitKey()
in case the delay expired with no key presses, use cv::waitKeyEx() to
rely on the old behavior.

For details see
https://github.com/opencv/opencv/pull/7866#issuecomment-269322846

diff --git a/opencv_trail_effect.cpp b/opencv_trail_effect.cpp
index 97b4aa7..5a4e928 100644 (file)
--- a/opencv_trail_effect.cpp
+++ b/opencv_trail_effect.cpp
@@ -204,7 +204,7 @@ int main(int argc, char *argv[])
                trail->draw(canvas);
 
                cv::imshow("Frame", canvas);
                trail->draw(canvas);
 
                cv::imshow("Frame", canvas);

-               if (cv::waitKey(30) >= 0)
+               if (cv::waitKeyEx(30) >= 0)

                        break;
 
                if (outputVideo.isOpened())
                        break;
 
                if (outputVideo.isOpened())