The ROX documentation says:
The playlist files are identified as plain text even though *.m3u is a defined glob. If I add #EXTM3U at the start of the file they are recognised as audio.How does the filer decide what icon to show for a file, and which program to use to open it?
For each file, the filer starts by working out its MIME-Type, as follows:
If the file's user.mime_type extended attribute it set, then that is its MIME type.
If the file's name matches a pattern in one of the globs file (usually, /usr/share/mime/globs) then the line in that file gives the type.
If the contents of the file match a pattern in one of the magic files (usually, /usr/share/mime/magic) then that gives the type.
Otherwise, it is text/plain (looks like text), application/x-executable (marked as executable) or application/x-octet-stream (doesn't look like UTF-8 text).
Do not edit the globs and magic files directly, as they are generated from some XML files by the update-mime-database command. If the filer isn't getting the right type for a file, you can use MIME-Editor to change the rules.
The transport stream files recorded by tvheadend or my satellite receiver are identified as executables even though *.ts is a defined glob. The ones I have edited are identified as video.mp2t which is correct.
So it seems that ROX filer and gnome-mpv may be using the magic numbers but not the globs. But the Gnome developers guide says that globs are preferred.
The files are on a FAT32 drive so they can't have extended attributes.
I presume there is some underlying linux function that ROX and gnome-mpv are using that is not configured correctly.
The files in /usr/share/mime all look sensible.
Does anyone have any idea what might be wrong?
It's not possible to set a run action when the MimeType is incorrect.
Thanks