OS X - .thumbnails folder

In this directory are stored blender’s thumbnails

This folder contain subfolders

  • fail/blender - filled by PNG empty files 1 by 1 px
  • large - filled by PNG thumbnails 256 by 256 px
  • normal - is empty folder

Thunbnails are dated probably from my last clean installation of OS in March 2016.

Is this expected behaviour? Or is it a bug?

  • “Large” folder contains already like 500 MB and thats only because I used thumbnail preview very lightly this year.
    Does exist any rule that deletes files after some date or size limit, or blender just generates new … ?

  • Folder named “Large” stores thumbnail size that doesnt match to any of the current thumbnail size - are these some “middle” size images for faster generating all available sizes in blender list?

  • Switching thumbnail size (large, thiny, …) does not generates any other files in “.thumbnail” directory so what is “Normal” folder good for?

  • What are these empty 1pixel files good for?

Thanks for more details.