On May 15 a development version 0.1.90 of Tumbler has been released targeting Xfce 4.14, this version is a port of Tumbler from the old obsolete dbus-glib binding to the new GDBus binding. In addition to the port, on May 28, a new version of tumbler 0.1.92 has been released. In this release, I have added a plugin that supports loading thumbnailers from *.thumbnailer files. The new plugin, called tumbler-desktop-thumbnailer, loads from $XDG_DATA_DIRS/thumbnailers/ all files with .thumbnailer as extension, those are desktop files of the following form.
[Thumbnailer Entry] Exec=/usr/bin/wine-exe-thumbnailer %i %o %u MimeType=application/x-ms-dos-executable;application/x-msdownload;applic ation/x-msi;application/x-ms-shortcut;application/x-dosexec
For a detailed description of the above desktop file as well as an example of such thumbnailer please see Customizing Thunar, the thumbnailer section.
To resume, the new desktop-thumbnailer registers a list of new thumbnailers found in $XDG_DATA_DIRS/thumbnailers/ (ex. /usr/share/thumbnailers/wine.thumbnailer) into Tumbler with their respective Mime Types. These thumbnailers are executed later on files with mimetype matches the one listed in the MimeType section.
In older versions of Tumbler, adding a new thumbnailer to Tumbler for more mimetypes, involved writing a C plugin for Tumbler. With the new desktop thumbnailer this can be done using a simple script and thumbnailer desktop file!
I have written a simple script that returns a wine png image for files with mimetype “application/x-dosexec”, and here is the result!