Re: [Bug-readline] partial word completion

[David Fang]

Hi Chet,
	Your suggestion worked, thanks for your help!  I just provided my 
own display hook that transformed the string pointers by munching up to 
the common prefix of the hierarchical name, and passed that to the 
standard display-matches function.  I had to append a call to 
rl_forced_update_display() to restore the line buffer. (code pasted below)

> The standard readline mechanism for multiple completions is an array of
> matches, where matches[0] contains the common prefix, and matches[1..n]
> contain the possible completions, including the common prefix.  This
> allows readline to sort, eliminate duplicates, and so on.

Ahh, I didn't about matches[0] being special before.
That explains a few things... :)

> > I would like this to behave similarly to directory completion:
> > % cd foo/bar/x<TAB>
> > % cd foo/bar/xx
>
> You need to handle the display of possible completions yourself.
> The way to do that is to `register' a function to display matches by
> assigning its address to rl_completion_display_matches_hook.  That
> function receives the list of matches in the form described above, the
> number of matches in the list, and the length in characters of the
> longest entry.
>
> Your code can manipulate the list of matches to remove the common
> prefix, if you'd like, but make sure that you keep any new common prefix
> in matches[0].  Readline provides a convenience function to display
> the contents of the array, rl_display_match_list(), which you can call
> with your modified array and the same two additional arguments your
> function received, modified appropriately.

For anyone interested, my display hook function looks like this:

// candidate matches can look like (hierarchical prefix always match):
// for set:
// x. x.foo x.bar x.baz
//
// desired behavior:
// prompt> x.<TAB>
// foo bar baz
// prompt> x.
// prompt> x.b<TAB>
// prompt> x.ba<TAB>
// bar baz

void
my_display_matches_hook(char** matches, int len, int max) {
if (len) {
        // find the last '.', if any
        char* tail = strrchr(matches[0], '.');
        if (tail) {
                const int dist = tail -matches[0] +1;   // past '.'
                std::vector<char*> mod_matches;
                mod_matches.reserve(len+1);
                mod_matches.push_back(matches[0]);
                int i=1;
                for ( ; i<=len; ++i) {
                        // remove common prefix
                        assert(matches[i]);
                        const size_t ml = strlen(matches[i]);
                        assert(ml > size_t(dist));
                        mod_matches.push_back(matches[i] +dist);
                }
                assert(max > dist);
                rl_display_match_list(&mod_matches[0], len, max -dist);
        } else {
                // use default printer
                rl_display_match_list(matches, len, max);
        }
        rl_forced_update_display();     // refresh prompt, line-buffer
}
}


Fang

David Fang
http://www.csl.cornell.edu/~fang/
http://www.achronix.com/