📅 January 4, 2018
“Thunar is not showing any thumbnails despite thumbnail generation enabled. Why?”
I ran into this issue in Linux Mint 18.3 Cinnamon when using the Thunar file manager. Traversing directories functioned fine, but no thumbnails were generated for media files, such a images, videos, and music containing album art.
Here is one technique I tried to make the thumbnails appear.
In Linux Mint 18.3 Cinnamon, Thunar is not installed by default. So, if you do not use Thunar, then this might not apply to you. However, if you do have Thunar installed and you use it, then this technique might help.
First, make sure you have Thunar installed and any plugins you might need. Check Synaptic Package Manager.
Install tumbler. Not absolutely certain if tumbler is still necessary for Thunar, but I noticed on my system that Thunar did not automatically generate thumbnails until it was installed.
In Thunar itself, open File Manger Preferences with Edit > Preferences > Display. Select Always for Show Thumbnails. This displays thumbnails for local and remote files.
Restart Thunar by closing all instances and running thunar -q at a command prompt.
Strangely, this was not enough to automatically generate thumbnails on my system. At first, I was tricked into thinking that Thunar was generating thumbnails when it really was not because Thunar will display thumbnails already generated by Nemo.
If thumbnails already exist in ~/.thumbnails or ~/.cache/thumbnails, regardless of what program creates them, then Thunar will display them. I wanted automatic thumbnail generation upon opening a directory within Thunar. To do this, I also had to perform these steps:
sudo apt install update-mime-database
sudo update-mime-database /usr/share/mime
To be certain that Thunar was generating thumbnails, I also cleared the thumbnail cache directories at ~/.cache/thumbnails and ~/.thumbnails.
After closing Thunar and reopening directories, thumbnails automatically generated using Thunar. I could see this by watching ~/.cache/thumbnails/normal populate as I traversed media directories using Thunar. New thumbnail files (.png) automatically appeared, and thumbnails were shown.
Thunar generated thumbnails for almost all media files. Images (png, jpg, gif) and videos (mkv, mp4) displayed fine, but embedded album art contained within music files, such as mp3 and flac, did not have thumbnails generated for them like Nemo would do. This seems to be a design issue regarding Thunar, so there is not a native way to resolve it. However, if another file manager, such as Nemo, pre-generates thumbnails for the music files, then Thunar will display the thumbnails for those music files.
“Why do this at all?”
To have a secondary file manager available in case the primary file manager (Nemo, in this case) falters. I have encountered a few situations where Nemo would unexpectedly crash — closing all open Nemo windows and, thus, losing my progress. Quite annoying. With another file manager ready, this situation is lessened by dividing the workload between two different file managers.