sxiv is an alternative to feh and qiv. Its only dependencies besides
xlib are imlib2 and giflib. The primary goal for writing sxiv is
to create an image viewer, which only has the most basic features
required for fast image viewing.
It has vi key bindings and works nicely with tiling window managers.
Its code base should be kept small and clean to make it easy for
you to dig into it and customize it for your needs.