Empty progress function

I have written a guetzli wrapper which works just fine. Because guetzli is so slow, it would make sense if it could indicate progress. So what I suggest is that you create an empty progress function, something like this:

void Progress(int percentage) {
// your callback goes here
}

That would work for me. I could send a window message to my wrapper which would use a progress bar. I admit I haven’t looked at the code since I use an older version of Visual Studio.