The mime type is a little text like image/jpeg
or application/pdf
that is used to identify the content of a file. Its main use is to determine what program can handle each file
Theres been this problem where the default program offered by debian were a very awkward one. Like trying to use the notepad.exe that comes with wine to open .txt
files. In linux we dont rely on extensions to determine the content of a file, but still wines registers itself as being able to handle text/plain
files using its wine-extension-txt.desktop
file
The reason this happens is that in some lightweight desktops (like xfce), it will default to the last program installed (or upgraded!!!) that can handle the file, unless you define a default one yourself
I fixed this weird behaviour a long time ago by using strace |grep home
to locate the file that was being used and updating it. In this case
~/.local/share/applications/mimeapps.list
It was fast, but I never really understood why it happened on the first place
This post found on planet debian digs a little deeper using a different but longer approach and was used to find the reason behind it. Good catch!