Bug#825418: evince-previewer: Should not register as the default viewer for PDFs or other documents

[Jason Crain]

On Thu, May 26, 2016 at 12:12:43PM -0700, Josh Triplett wrote:
> Then evince-previewer should not register itself as the default viewer
> for various file types, including PDFs.  By default, opening a PDF from
> mutt or another program that respects the mailcap database (as updated
> by update-mime) will open that PDF in evince-previewer, rather than
> evince.  If evince-previewer only exists to handle print previews (which
> seems consistent with its window title of "Print Preview"), then it
> should not register itself as a handler for the MIME types that evince
> does.
> 
> /usr/share/applications/evince-previewer.desktop and
> /usr/share/applications/evince.desktop both contain an identical
> MimeType line.  I don't see anything in either file that sets a
> priority, so I don't see any way that an application (or update-mime)
> could know to prefer one over the other.

There is not a way to specify priorities for applications using .desktop
files.  The FDO spec sort of has a way to specify global defaults in a
/usr/share/applications/mimeapps.list file, but it doesn't have a good
priority mechanism and Debian doesn't include that file anyway, leaving
it up to either the desktop environment or someone using xdg-mime to set
per-user defaults.

I think it might be a good idea to remove the mime info from
evince-previewer.desktop though.  I don't see anything break when I
change it to "MimeType=" and as a bonus, this removes it from some menus
where it shouldn't be visible anyway.