Some more testing.
I've tried to use my .mailcap: added a line
video/asx; /usr/bin/vlc %s --my-command-line-arguments
It is used by SM (without restart!) since the default app proposed now is
/usr/bin/vlc instead of totem. VLC starts but the command-line arguments
are ignored. Using
video/asx; /usr/bin/some-wrapper-script %s
doesn't work at all (VLC doesn't start).
Since the arguments used are supposed to dump output to some file in my
/home, I thought there might be a problem with file permissions, but
directing output to a file in /tmp doesn't change anything.
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