Infinite Loop when viewing more than N_VIEWAHEAD thumbnails
The thumbnailer has an infinite loop in phase UPDATE_VISIBLE when there are more than N_VIEWAHEAD (currently 50) thumbnails visible:
_gth_file_list_thumbnailer_iterate()
picks a particular thumbnail as the next one
job->update_in_view
gets computed to false, so the job becomes a CREATING job, not a LOADING one.
gth_thumb_loader_has_valid_thumbnail()
returns true, since the thumbnail is ready is on disk, turning the thumbnail to CREATED.
_thumbnail_loaded()
returns false, since the thumbnails is only CREATED.
... which means _gth_file_list_thumbnailer_iterate()
picks the /very same/ thumbnail as the next job.
--> infinite loop.
A fix would turn the constant N_VIEWAHEAD into a variable that depends on the actual visible area.
As a mitigation I suggest to increase N_VIEWAHEAD significantly.