This might also be useful for ProjectOrganizer plugin. It could simplify the code introduced https://github.com/geany/geany-plugins/pull/1290, if the project opening and file parsing happened after Geany opens all the files in session.
I'm just afraid that the result would be "stuck on loaded document" instead of "stuck on nothing open" (which looks better) so we'd be back where we were with the idle function...