cv2.imshow() displaying blank, unresponsive window [duplicate] - macos

Question

I'm working right out of a book, and copied the following code (essentially the openCV equivalent of "hello world"):
//helloCV.cpp
#include <opencv2/opencv.hpp>
int main(int argc, char** argv){
cv::Mat img = cv::imread(argv[1], -1);
if (img.empty()) return -1;
cv::namedWindow("Example1", cv::WINDOW_AUTOSIZE);
cv::imshow("Example1", img);
cv::waitKey(0);
cv::destroyWindow("Example1");
return 0;
}//main
Unfortunately, when I run this code, I get a window with the header and nothing in it:
I suspect that I've messed up the environment or some such when installing OpenCV, but cmake is throwing no errors, and the code runs as expected, exiting correctly on a keystroke and all of that, with the glaring exception of a lack of a displayed photo.
Any tips?
Thanks!

Answer 1

Thanks to #DanMašek for the lead on this one, and to all the people on this page: http://answers.opencv.org/question/160201/video-window-not-loading-frame/
To repeat what they said, what worked for me was the following:
To resolve this, locate the file window_cocoa.mm; if built from source it'll be in opencv/modules/highgui/src.
Change the following:
#implementation CVView
#if defined(__LP64__)
#synthesize image;
#else // 32-bit Obj-C does not have automatic synthesize
#synthesize image = _image;
#endif
To this:
#implementation CVView
#synthesize image = _image;
Do the same thing for the CVWindow and CVSlider implementations to accommodate videos as well.
Recompile OpenCV and test out your code.
Hope this helps other people struggling with this issue!