todo.txt

- if active_idxs is empty in loaded_dir, things just crash
  - happens e.g. if you filter for a rating that hasn't been assigned to anything
  - hide all "current idx" dependent api behind another api object
    - current path, current image, current rating, etc. basically everything that indexes into active_idxs

  alternative if to make current_idx an option that's None if active_idxs is empty, but then everything talking about current returns options, so why bother

- check that load updates are issued when filter is changed. 
  - seeing some cases where right after changing filter the image to the right is still loading

- fix phantom duplicate inputs
  - sometimes you skip ahead 2 images instead of 1
  - current theory is that this is somehow linked to the texture upload pause

- figure out why worker_pool does a 1s wait before executing any worker task
  There's no comment on the line, and the commit that added it has no further context either.

- Feature: Allow marking non-adjacent pictures in some way then flick just between those.
  Useful for when I end up with the same motif with some other photos in between, and I want to pick one out of the set.

- Jump to start/end shortcuts
  If I go through the list once, then filter and want to go from the start again, getting there is laborious with just the "skip 10" controls.

- Allow for easier scroll without load pauses
  Scrolling through pictures quickly is still slow because there's a lot of loading happening. If I just want to skip ahead 30 it should be fast, and only when I rest somewhere should it start loading (or loading should have no impact on UI times, and loads that got initiated shouldn't block later loads if they'll be immediately irrelevant).

- Thumbnail view
  Allow for some alternate view that shows e.g. a grid of all the images that can be scrolled, to make it easier to orient yourself in the set.