This is something I wanted, and in response to https://sourceforge.net/tracker/?func=detail&aid=2819448&group_id=146377&atid=764988
This adds an option in the preferences which is enabled by default to show an indicator of the current page or pages for two seconds when it isn't visible elsewhere (fullscreen when everything is hidden, or when the statusbar is hidden).
The color of the text that is displayed is the inverse of the background color behind it. This works decently even with the buggy implementation of background color that is currently in the default release, but it works better if you fix that. I submitted a patch that fixes dynamic background color choosing a bit ago.
I'm submitting a second patch along with it that goes with my extra toolbars options patch, since the preferences that are referenced in this patch are changed in that patch.