System information (version)

• OpenCV => 4.5.3
• Operating System / Platform => Windows 10 64 Bit
• Compiler => Visual Studio 2019

Steps to reproduce

int main()
{
Mat img(720, 1280, CV_8UC3, Scalar(0xff, 0xff, 0xff));
imshow("img", img);
int key = waitKey(0);
cout << "return " << key << endl;
}