How to add find-previous in xdvi or findPrevious in xpdf for vi keybindings?

Is there a way to add a find-previous f开发者_高级运维unction in xdvi or a findPrevious function in xpdf? Those would be equivalent to a function that brings up the search dialog with the "Search backwards" option already checked.

I need such functions in order to define keybindings

bind ? any findPrevious

in my .xpdfrc and

xdvi.mainTranslations: #override\
                                 <Key>?:find-previous()

in my .Xdefaults. I'd then have a complete set of vi-like keybindings in both programs.

You may have to change the code of xpdf. I read the source code of xpdf once, it provides the search-backwards function, but does not give a key binding.