It would be great if vifm could try a secondary fileviewer if the first one exits with a non-zero code. This request stems from the script I'm working on in #1090.

For example, if I have the the following in my vifmrc

fileviewer {*.bmp,*.jpg,*.jpeg,*.png,*.gif,*.xpm},<image/*>
            \ sixel-preview image %c %pw %ph %pd %pc,
            \ identify %f

and add the following to the top of the sixel-preview script

ensure_installed() { command -v "$1" >/dev/null 2>&1 || exit 1; }
ensure_installed img2sixel
ensure_installed exiftool

I'd like vifm to move on to the identify %f fileviewer if neither img2sixel nor exiftool are installed.