[WIP] Fix opening files, as xdg-open fails for terminal programs.

[martinsifrar]

The issue

When using rofi -show filebrowser, opening a file silently fails if the associated program is a terminal program. In my case, associating

text/plain=nvim.desktop

results in files not being open. A little digging revealed file_browser_mode_result in modes/filebrowser.c, the run_in_term argument is always FALSE

helper_execute_command(cdir, cmd, FALSE, NULL);
                                   ^
                                   gboolean run_in_term

If I manually set it to 1, the text file is opened in Vim as I would expect. But seeing if run_in_term should be set would require parsing the associated programs .desktop entry.

Suggestion

I suggest that instead of xdg-open, the Gio function launch_default_for_uri is used for opening regular files in their associated programs (this PR).

Possible problem

Rofi only uses its rofi-sensible-terminal script, while GLib has a somewhat weird way of handling terminal selection (see https://gitlab.gnome.org/GNOME/glib/-/issues/2293), which could maybe trip up some users. Because of this, I denoted the PR as WIP.