If we discover inside the loop that restart has been set to true (by render()), we break out of the loop immediately, so that the control quickly returns to the very top of the outer loop (the forever loop) and we fetch the new rendering parameters.

However when I look the code I see the break is:

void RenderThread::run()
{
    forever {
        //    ...
        while (pass < NumPasses) {
            // ...
            for (int y = -halfHeight; y < halfHeight; ++y) {
                if (restart)
                    break;

The break will break the for loop but not he while loop. I don't see anything that breaks the while loop to "quickly return" to the forever loop.

Am I missing something or is this a bug?

Thanks