Loading iframe with with load image

I am using the iframe option.

When I use the class=”fancybox iframe” it doesn’t work. When I use the class=”fancybox-iframe” it works, but it opens the overlay image and then takes a few seconds to load the html page.

Is there a way to have it show the little loading image until it’s ready to display the html page?

https://ww.wp.xz.cn/plugins/easy-fancybox/