https://github.com/lrsjng/pagemap https://github.com/lrsjng/pagemap looks viable. But it uses a canvas and redraws. While the post's website renders a copy of

https://github.com/lrsjng/pagemap https://github.com/lrsjng/pagemap looks viable. But it uses a canvas and redraws. While the post's website renders a copy of the page in a <div> and scroll it. As you can check by inspecting the div.