Misplaces cached background image thumbnails

[Egmont Koblinger]

Wipe our your ~/.cache/thumbnails directory.

Open unity-control-center -> Appearance.

Check the contents of ~/.cache/thumbnails.

Notice that thumbnails of 256px (the bigger dimension) are placed under the "normal" subdirectory.

According to the specs at
  https://specifications.freedesktop.org/thumbnail-spec/thumbnail-spec-latest.html
and
  https://developer.gnome.org/gnome-desktop3/stable/GnomeDesktopThumbnailFactory.html
this is incorrect, the "normal" directory should contain thumbnails of 128px, whereas the "large" directory stores thumbnails of 256px.

This means that this cache is at a nonstandard location and as such, is not shared with the rest of the apps.

All the other thumbnails I've gathered during years of using my system are under the proper subdirectory. gnome-shell and gnome-control-center also stores them under the proper one, so I suspect it's a downstream Unity bug, not an upstream GNOME one.

ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: unity-control-center 15.04.0+17.04.20170402.6-0ubuntu1
ProcVersionSignature: Ubuntu 4.10.0-15.17-generic 4.10.5
Uname: Linux 4.10.0-15-generic x86_64
ApportVersion: 2.20.4-0ubuntu3
Architecture: amd64
CurrentDesktop: Unity:Unity7
Date: Sat Apr 8 11:49:38 2017
InstallationDate: Installed on 2016-11-09 (149 days ago)
InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Release amd64 (20161012.2)
SourcePackage: unity-control-center
UpgradeStatus: Upgraded to zesty on 2017-04-05 (2 days ago)