currently broken attempt to allow tab-completion after arbitrary prefixes

gui-completion.c

    if (size > 0)
    {
        i = pos;
        pos_start = i;
        ignore_prefix_chars = !CONFIG_STRING(config_completion_ignore_prefix_chars)
            && !CONFIG_STRING(config_completion_ignore_prefix_chars)[0];
        /* only backtrack on a space, other characters would be unexpected */
        if (data[i] == ' ') // Guards against a double space?
        {
            if ((i > 0) && (data[i-1] != ' ') && (ignore_prefix_chars 
                || (!strchr (CONFIG_STRING(config_completion_ignore_prefix_chars),
                             data[i-1]))))
            {
                i--;
                while ((i >= 0) && (data[i] != ' ') && (ignore_prefix_chars 
                    || (!strchr (CONFIG_STRING(config_completion_ignore_prefix_chars),
                                 data[i]))))
                {
                    i--;
                }
                pos_start = i + 1;
            }
        }
        else
        {
            while ((i >= 0) && (data[i] != ' ') && (ignore_prefix_chars 
                || (!strchr (CONFIG_STRING(config_completion_ignore_prefix_chars),
                             data[i]))))
            {
                i--;
            }
            pos_start = i + 1;
        }