I've been quite busy since the last article, which will be still going on for a while, so please forgive me if I'm not quite responsive. Just feel free to poke me by email if I have not reply your message in 3 days.
I had planned to add image optimizations in v0.9, while there are APIs in poppler to detect the area of changes, there is not such convenient APIs for outputting (a partial of the background), I might still need to work on this, the ideal way is to avoid bring more modified poppler code back to pdf2htmlEX (then maintain them).
Recently there are pull requests about key shortcuts and UI events. (Thank you!)
But they required to inject global handlers in the web pages, which might not be desirable for some users who need only nothing but HTML pages. I'm now considering to create a new mode, say standalone mode, which means the user is intended to use the complete package produced by pdf2htmlEX. In this way we can add more UI features without affect other users. I'm still thinking about the logic, whether this should be a new set of files (manifect and other files) or simply a switch in JS.