To write the Library Card element (Cd) in the index.

§1. The Library Card is part of the Contents index, and is intended as a natural way to present bibliographic data to the user. In effect, it's a simplified form of the iFiction record, without the XML overhead.

void CardElement::render?Usage of CardElement::render:
The Periodic Table - §4(OUTPUT_STREAM, index_session *session) {
    inter_tree *I = Indexing::get_tree(session);
    inter_package *pack = InterPackage::from_URL(I, I"/main/completion/bibliographic");

    HTML_OPEN("p");
    IndexUtilities::anchor(OUT, I"LCARD");
    HTML::begin_html_table(OUT, "*bg_images/indexcard.png", FALSE, 0, 3, 3, 0, 0);
    CardElement::Library_Card_entry(OUT, "Story title", pack, I"^title", I"Untitled");
    CardElement::Library_Card_entry(OUT, "Story author", pack, I"^author", I"Anonymous");
    CardElement::Library_Card_entry(OUT, "Story headline", pack, I"^headline", I"An Interactive Fiction");
    CardElement::Library_Card_entry(OUT, "Story genre", pack, I"^genre", I"Fiction");
    int E = (int) Metadata::read_optional_numeric(pack, I"^episode");
    text_stream *series_name = Metadata::optional_textual(pack, I"^series");
    if (series_name) {
        TEMPORARY_TEXT(episode_text)
        WRITE_TO(episode_text, "%d of %S", E, series_name);
        CardElement::Library_Card_entry(OUT, "Episode", pack, NULL, episode_text);
        DISCARD_TEXT(episode_text)
    }
    CardElement::Library_Card_entry(OUT, "Release number", pack, I"^release", I"1");
    CardElement::Library_Card_entry(OUT, "Story creation year", pack, I"^year", I"(This year)");
    CardElement::Library_Card_entry(OUT, "Language of play", pack, I"^language", I"English");
    CardElement::Library_Card_entry(OUT, "IFID number", pack, I"^IFID", NULL);
    CardElement::Library_Card_entry(OUT, "Story description", pack, I"^description", I"None");
    HTML::end_html_table(OUT);
    HTML_CLOSE("p");
}

§2. This uses:

void CardElement::Library_Card_entry?Usage of CardElement::Library_Card_entry:
§1(OUTPUT_STREAM, char *field, inter_package *pack,
    text_stream *key, text_stream *t) {
    text_stream *col = I"303030";
    if (Str::eq(key, I"^title")) col = I"803030";
    HTML::first_html_column_nowrap(OUT, 0, NULL);
    HTML::begin_colour(OUT, col);
    HTML_OPEN_WITH("span", "class=\"typewritten\"");
    WRITE("%s", field);
    HTML_CLOSE("span");
    HTML::end_colour(OUT);
    HTML::next_html_column(OUT, 0);
    HTML::begin_colour(OUT, col);
    HTML_OPEN_WITH("span", "class=\"typewritten\"");
    HTML_OPEN("b");
    CardElement::index_variable(OUT, pack, key, t);
    HTML_CLOSE("b");
    HTML_CLOSE("span");
    HTML::end_colour(OUT);
    HTML::end_html_row(OUT);
}

§3. And both of those features use:

void CardElement::index_variable?Usage of CardElement::index_variable:
§2(OUTPUT_STREAM, inter_package *pack,
    text_stream *key, text_stream *t) {
    if (key) {
        if (Str::eq(key, I"^release")) {
            int R = (int) Metadata::read_optional_numeric(pack, key);
            if (R > 0) { WRITE("%d", R); return; }
        } else {
            text_stream *matter = Metadata::optional_textual(pack, key);
            if (matter) { WRITE("%S", matter); return; }
        }
    }
    WRITE("%S", t);
}