To provide for weaving in the standard maths and science typesetting software, TeX, and its numerous variants.

§1. Creation. 

void LaTeXWeaving::create(void) {
    weave_format *wf = WeavingFormats::create_weave_format(I"LaTeX", I".tex");
    METHOD_ADD(wf, RENDER_FOR_MTID, LaTeXWeaving::render_LaTeX);
}

§2. Markdown rendering instructions. While the code in this section renders the weave tree, the actual commentary (along with other fragments, such as comments in code, depending on the conventions used) is stored in Markdown, and needs to be handed over to the code in Markdown to TeX (in foundation).

That needs a set of instructions, to say what kind of Markdown, how we want it rendered, and so on.

markdown_render LaTeXWeaving::Markdown_instructions(weave_order *wv) {
    markdown_render rdr = MDRender::contextual_LaTeX(
        WebNotation::commentary_variation(wv->weave_web),
        STORE_POINTER_weave_order(wv));
    markdown_render *prdr = &rdr;
    METHOD_ADD(prdr, NAME_COLOUR_MTID, WeavingFormats::name_colour);
    METHOD_ADD(prdr, NAME_COLOUR_SCHEME_MTID, WeavingFormats::name_colour_scheme);
    METHOD_ADD(prdr, BEGIN_COLOURING_MTID, WeavingFormats::begin_colouring);
    METHOD_ADD(prdr, COLOUR_LINE_MTID, WeavingFormats::colour_line);
    METHOD_ADD(prdr, RESOLVE_LINK_MTID, WeavingFormats::resolve_link);
    METHOD_ADD(prdr, NAME_ANCHOR_MTID, LaTeXWeaving::name_anchor);
    METHOD_ADD(prdr, NOTIFY_IMAGE_MTID, LaTeXWeaving::notify_image);
    METHOD_ADD(prdr, RENDER_GADGET_MTID, LaTeXWeaving::render_gadget);
    METHOD_ADD(prdr, RENDER_UL_AS_CAROUSEL_MTID, LaTeXWeaving::render_ul_as_carousel);
    return rdr;
}

void LaTeXWeaving::name_anchor(markdown_render *rdr, text_stream *OUT, void *clabel) {
    ls_line_label *label = (ls_line_label *) clabel;
    ls_line *line = LineLabels::destination(label);
    LaTeXWeaving::line_anchor(OUT, line);
}

void LaTeXWeaving::line_anchor(text_stream *OUT, ls_line *line) {
    ls_section *S = LiterateSource::section_of_line(line);
    if (S) WRITE("s%d", S->allocation_id);
    WRITE("line%d", line->sequence_number_in_section);
}

§3. Rendering. 

void LaTeXWeaving::render_LaTeX(weave_format *self, text_stream *OUT, heterogeneous_tree *tree) {
    weave_document_node *C = RETRIEVE_POINTER_weave_document_node(tree->root->content);
    LaTeX_render_state trs;
    Initialise the render state3.2;
    Trees::traverse_from(tree->root, &LaTeXWeaving::render_visit, (void *) &trs, 0);
}

§3.1. The following state will be carried through the traverse.

classdef LaTeX_render_state {
    struct text_stream *OUT;
    struct weave_order *wv;
    struct colour_scheme *colours;
    struct markdown_render rdr;
    int no_need_for_page_break;
    int max_label_width;
    int holon_defined;
    int commentary_rendered;
    ls_paragraph *current_par;
} LaTeX_render_state;

§3.2. Initialise the render state3.2 =

    trs.OUT = OUT;
    trs.wv = C->wv;
    trs.colours = Swarm::ensure_colour_scheme(C->wv, I"Colours", I"");
    trs.rdr = LaTeXWeaving::Markdown_instructions(C->wv);
    trs.no_need_for_page_break = FALSE;
    trs.max_label_width = 0;
    trs.holon_defined = FALSE;
    trs.commentary_rendered = FALSE;
    trs.current_par = NULL;

§4. So, then, the visiting function, called on each node. C does not allow switch statements whose cases are not literal constants, so there's a big contrived if instead. But it is morally a switch.

int LaTeXWeaving::render_visit(tree_node *N, void *state, int L) {
    LaTeX_render_state *trs = (LaTeX_render_state *) state;
    text_stream *OUT = trs->OUT;

    /* Document superstructure */

         if (N->type == weave_document_node_type) Render document4.2
    else if (N->type == weave_head_node_type) Render head4.3
    else if (N->type == weave_body_node_type) Skip4.1
    else if (N->type == weave_tail_node_type) Render tail4.4

    /* Large-scale structure */

    else if (N->type == weave_chapter_node_type) Skip4.1
    else if (N->type == weave_chapter_header_node_type) Render chapter header4.5
    else if (N->type == weave_chapter_footer_node_type) Skip4.1
    else if (N->type == weave_section_node_type) Skip4.1
    else if (N->type == weave_section_header_node_type) Render section header4.6
    else if (N->type == weave_section_footer_node_type) Skip4.1
    else if (N->type == weave_section_purpose_node_type) Render section purpose4.7
    else if (N->type == weave_toc_node_type) Render toc4.8
    else if (N->type == weave_toc_line_node_type) Render toc line4.9

    /* Small-scale structure */

    else if (N->type == weave_subheading_node_type) Render subheading4.10
    else if (N->type == weave_subsubheading_node_type) Render subsubheading4.11
    else if (N->type == weave_paragraph_heading_node_type) Render paragraph heading4.12
    else if (N->type == weave_material_node_type) Render material4.13

    /* Code-like material */

    else if (N->type == weave_holon_declaration_node_type) Render holon declaration4.14
    else if (N->type == weave_code_line_node_type) Render code line4.15
    else if (N->type == weave_holon_usage_node_type) Render holon usage4.16
    else if (N->type == weave_tangler_command_node_type) Skip4.1
    else if (N->type == weave_verbatim_node_type) Render verbatim4.17
    else if (N->type == weave_source_code_node_type) Render source code4.18
    else if (N->type == weave_function_defn_node_type) Render function defn4.19
    else if (N->type == weave_function_usage_node_type) Render function usage4.20
    else if (N->type == weave_comment_in_holon_node_type) Render comment in holon4.21
    else if (N->type == weave_defn_node_type) Render defn4.22

    /* Commentary and gadget material */

    else if (N->type == weave_markdown_node_type) Render Markdown4.23
    else if (N->type == weave_audio_node_type) Skip4.1
    else if (N->type == weave_carousel_slide_node_type) Render carousel slide4.24
    else if (N->type == weave_download_node_type) Skip4.1
    else if (N->type == weave_embed_node_type) Skip4.1
    else if (N->type == weave_figure_node_type) Render figure4.25
    else if (N->type == weave_raw_HTML_node_type) Skip4.1
    else if (N->type == weave_video_node_type) Skip4.1

    /* Paragraph tail material */

    else if (N->type == weave_index_begins_node_type) Render index begins4.26
    else if (N->type == weave_index_lemma_node_type) Render index lemma4.27
    else if (N->type == weave_index_ends_node_type) Render index ends4.28
    else if (N->type == weave_endnote_node_type) Render endnote4.29
    else if (N->type == weave_locale_node_type) Render locale4.30
    else if (N->type == weave_endnote_text_node_type) Render endnote text4.31

    else internal_error("no HTML rendering for this node type");
    return TRUE;
}

§4.1. Skip4.1 =

    ;

§4.2.1. By default, the visitor function returns TRUE at each node (see above). This tells the tree-traversing machinery to continue recursing down through that node's children after the node itself has been visited.

Some nodes, however, will want to render something, then recurse downwards, then render something further. They can do this by using the following holon to perform the recursion, but must then explicitly return FALSE, or else the child nodes will end up being visited a second time.

Recurse the renderer through children nodes4.2.1 =

    for (tree_node *M = N->child; M; M = M->next)
        Trees::traverse_from(M, &LaTeXWeaving::render_visit, (void *) trs, L+1);

§4.2. Document superstructure renderers. These are just comments.

Render document4.2 =

    trs->wv->current_insertion_points[PRE_DOCUMENT_WEAVEINSCRIPTION] = Str::len(OUT);
    WRITE("\n\\begin{document}\n");
    trs->wv->current_insertion_points[DOCUMENT_WEAVEINSCRIPTION] = Str::len(OUT);
    Recurse the renderer through children nodes4.2.1;
    WRITE("\\end{document}\n");
    return FALSE;

§4.3. Render head4.3 =

    weave_head_node *C = RETRIEVE_POINTER_weave_head_node(N->content);
    WRITE("%% %S\n", C->banner);

§4.4. Render tail4.4 =

    weave_tail_node *C = RETRIEVE_POINTER_weave_tail_node(N->content);
    WRITE("%% %S\n", C->rennab);

§4.5. Large-scale structure renderers. Render chapter header4.5 =

    weave_chapter_header_node *C = RETRIEVE_POINTER_weave_chapter_header_node(N->content);
    if (Str::ne(C->chap->ch_range, I"S")) {
        WRITE("\\vfill\\eject");
        WRITE("\\inwebanchor{ch%S}\\label{item:ch%S}\n", C->chap->ch_range, C->chap->ch_range);
        LaTeXWeaving::general_heading(OUT, &(trs->rdr), trs->wv,
            FIRST_IN_LINKED_LIST(ls_section, C->chap->sections), NULL, C->chap->ch_title,
            3, FALSE);
        if (Str::len(C->chap->rubric) > 0)
            MDRender::stream(OUT, &(trs->rdr), C->chap->rubric, 0);
        WRITE("\\bigskip\n");
        trs->no_need_for_page_break = TRUE;
    }

§4.6. Render section header4.6 =

    weave_section_header_node *C = RETRIEVE_POINTER_weave_section_header_node(N->content);
    if (trs->no_need_for_page_break == FALSE) WRITE("\\vfill\\eject");
    WRITE("\\inwebanchor{se%S}\\label{item:se%S}\n", C->sect->sect_range, C->sect->sect_range);
    LaTeXWeaving::general_heading(OUT, &(trs->rdr), trs->wv, C->sect, NULL,
        C->sect->sect_title, 2, FALSE);
    trs->no_need_for_page_break = FALSE;
    WRITE("\\followsheadingtrue\n");

§4.7. Render section purpose4.7 =

    weave_section_purpose_node *C = RETRIEVE_POINTER_weave_section_purpose_node(N->content);
    WRITE("\\smallskip\\par\\noindent{\\it ");
    MDRender::stream(OUT, &(trs->rdr), C->purpose, 0);
    WRITE("}\\smallskip\\noindent\n");
    WRITE("\\followsheadingtrue\n");

§4.8. The Table of Contents at the top of a section:

Render toc4.8 =

    WRITE("\\medskip\\hrule\\smallskip\\par\\noindent\\sectiontoctext{");
    for (tree_node *M = N->child; M; M = M->next) {
        Trees::traverse_from(M, &LaTeXWeaving::render_visit, (void *) trs, L+1);
        if (M->next) WRITE("; ");
    }
    WRITE("}\\par\\medskip\\hrule\\bigskip\n");
    WRITE("\\followsheadingtrue\n");
    return FALSE;

§4.9. Render toc line4.9 =

    weave_toc_line_node *C = RETRIEVE_POINTER_weave_toc_line_node(N->content);
    LaTeXWeaving::locale(OUT, &(trs->rdr), C->para, NULL, C->para);
    WRITE("~");
    MDRender::stream(OUT, &(trs->rdr), C->text2, 0);

§4.10. Small-scale structure renderers. Render subheading4.10 =

    weave_subheading_node *C = RETRIEVE_POINTER_weave_subheading_node(N->content);
    WRITE("\\par\\noindent{\\bf ");
    MDRender::stream(OUT, &(trs->rdr), C->text, 0);
    WRITE("}\\medskip\n");

§4.11. Render subsubheading4.11 =

    weave_subsubheading_node *C = RETRIEVE_POINTER_weave_subsubheading_node(N->content);
    WRITE("\\par\\noindent{\\bf ");
    MDRender::stream(OUT, &(trs->rdr), C->text, 0);
    WRITE("}\\medskip\n");

§4.12. Render paragraph heading4.12 =

    weave_paragraph_heading_node *C =
        RETRIEVE_POINTER_weave_paragraph_heading_node(N->content);
    if (LiterateSource::par_has_visible_number(C->para)) {
        text_stream *titling = LiterateSource::par_title(C->para);
        if (Str::len(titling) == 0)
            LaTeXWeaving::general_heading(OUT, &(trs->rdr), trs->wv, LiterateSource::section_of_par(C->para),
                C->para, I"", 0, FALSE);
        else
            LaTeXWeaving::general_heading(OUT, &(trs->rdr), trs->wv, LiterateSource::section_of_par(C->para),
                C->para, titling, 1, FALSE);
    } else {
        WRITE("\\par\n");
    }
    trs->holon_defined = FALSE;
    trs->commentary_rendered = FALSE;
    trs->current_par = C->para;
    WRITE("\\inwebanchor{");
    LaTeXWeaving::paragraph_link(OUT, C->para);
    WRITE("}");

§4.13. Render material4.13 =

    weave_material_node *C = RETRIEVE_POINTER_weave_material_node(N->content);
    if (C->material_type == COMMENTARY_MATERIAL)
        Deal with a commentary material node4.13.1
    else if (C->material_type == CODE_MATERIAL)
        Deal with a code material node4.13.2
    else if (C->material_type == FOOTNOTES_MATERIAL)
        Deal with a footnotes material node4.13.3
    else if (C->material_type == ENDNOTES_MATERIAL)
        Deal with a endnotes material node4.13.4
    else if (C->material_type == HOLON_DECLARATION_MATERIAL)
        Deal with a holon material node4.13.5
    else if (C->material_type == DEFINITION_MATERIAL)
        Deal with a definition material node4.13.6;
    return FALSE;

§4.13.1. Deal with a commentary material node4.13.1 =

    Recurse the renderer through children nodes4.2.1;
    WRITE("\n");
    trs->commentary_rendered = TRUE;

§4.13.2. Deal with a code material node4.13.2 =

    if (C->styling) {
        TEMPORARY_TEXT(csname)
        WRITE_TO(csname, "%S-Colours", C->styling->language_name);
        trs->colours = Swarm::ensure_colour_scheme(trs->wv,
            csname, C->styling->language_name);
        DISCARD_TEXT(csname)
    }
    if (trs->holon_defined) WRITE("\\beginlinestighter\n");
    else WRITE("\\beginlines\n");
    trs->max_label_width = 0;
    for (tree_node *M = N->child; M; M = M->next)
        if (M->type == weave_code_line_node_type) {
            weave_code_line_node *MC = RETRIEVE_POINTER_weave_code_line_node(M->content);
            if ((MC->line) && (LineLabels::label_width(MC->line) > trs->max_label_width))
                trs->max_label_width = LineLabels::label_width(MC->line);
        }
    Recurse the renderer through children nodes4.2.1;
    trs->max_label_width = 0;
    WRITE("\\endlines\n");

§4.13.3. Deal with a footnotes material node4.13.3 =

    return FALSE;

§4.13.4. Deal with a endnotes material node4.13.4 =

    Recurse the renderer through children nodes4.2.1;

§4.13.5. Deal with a holon material node4.13.5 =

    Recurse the renderer through children nodes4.2.1;
    WRITE("\n");

§4.13.6. Deal with a definition material node4.13.6 =

    WRITE("\\beginlinestighter\n");
    Recurse the renderer through children nodes4.2.1;
    WRITE("\\endlines\n");

§4.14. Code-like material renderers. Render holon declaration4.14 =

    if (trs->commentary_rendered) WRITE("\\par\\smallskip\\noindent\n");
    weave_holon_declaration_node *C = RETRIEVE_POINTER_weave_holon_declaration_node(N->content);
    LaTeXWeaving::holon_name(OUT, &(trs->rdr), C->holon, TRUE);
    trs->holon_defined = TRUE;

§4.15. Render code line4.15 =

    weave_code_line_node *C = RETRIEVE_POINTER_weave_code_line_node(N->content);
    WRITE("\\hskip1em ");
    if (trs->max_label_width > 0) {
        if (LineLabels::labelled(C->line)) {
            WRITE("\\inwebanchor{");
            LaTeXWeaving::line_anchor(OUT, C->line);
            WRITE("}");
            WRITE("|");
            int n = trs->max_label_width - Str::len(LineLabels::label_text(C->line));
            while (n > 0) { WRITE(" "); n--; }
            WRITE("%S |{$\\Rightarrow$}", LineLabels::label_text(C->line));
        } else {
            WRITE("|");
            int n = trs->max_label_width + 1;
            while (n > 0) { WRITE(" "); n--; }
            WRITE("|\\phantom{$\\Rightarrow$}");
        }
        WRITE("\\hskip1em ");
    }
    Recurse the renderer through children nodes4.2.1;
    WRITE("\n");
    return FALSE;

§4.16. Render holon usage4.16 =

    weave_holon_usage_node *C = RETRIEVE_POINTER_weave_holon_usage_node(N->content);
    LaTeXWeaving::holon_name(OUT, &(trs->rdr), C->holon, FALSE);

§4.17. Render verbatim4.17 =

    weave_verbatim_node *C = RETRIEVE_POINTER_weave_verbatim_node(N->content);
    TEMPORARY_TEXT(colouring)
    for (int i=0; i<Str::len(C->content); i++) PUT_TO(colouring, CHARACTER_COLOUR);
    MDRenderLaTeX::render_syntax_coloured(OUT, &(trs->rdr), C->content, colouring, NULL);
    DISCARD_TEXT(colouring)

§4.18. Render source code4.18 =

    weave_source_code_node *C =
        RETRIEVE_POINTER_weave_source_code_node(N->content);
    MDRenderLaTeX::render_syntax_coloured(OUT, &(trs->rdr), C->matter, C->colouring, NULL);

§4.19. Render function defn4.19 =

    weave_function_defn_node *C =
        RETRIEVE_POINTER_weave_function_defn_node(N->content);
    WRITE("|");
    MDRenderLaTeX::change_colour(OUT, &(trs->rdr), FUNCTION_COLOUR, NULL);
    WRITE("%S", C->fn->function_name);
    MDRenderLaTeX::change_colour(OUT, &(trs->rdr), PLAIN_COLOUR, NULL);
    WRITE("|");
    return FALSE;

§4.20. Render function usage4.20 =

    weave_function_usage_node *C =
        RETRIEVE_POINTER_weave_function_usage_node(N->content);
    TEMPORARY_TEXT(colouring)
    for (int i=0; i<Str::len(C->fn->function_name); i++) PUT_TO(colouring, FUNCTION_COLOUR);
    MDRenderLaTeX::render_syntax_coloured(OUT, &(trs->rdr), C->fn->function_name, colouring, NULL);
    DISCARD_TEXT(colouring)
    return FALSE;

§4.21. Render comment in holon4.21 =

    weave_comment_in_holon_node *C = RETRIEVE_POINTER_weave_comment_in_holon_node(N->content);
    TEMPORARY_TEXT(cm)
    TEMPORARY_TEXT(col)
    WRITE_TO(cm, "%S", C->comment_open);
    WRITE_TO(cm, "%S", C->raw);
    WRITE_TO(cm, "%S", C->comment_close);
    for (int i=0; i<Str::len(cm); i++) PUT_TO(col, COMMENT_COLOUR);
    int starts = FALSE;
    if (N == N->parent->child) starts = TRUE;
    WRITE("|");
    LaTeXWeaving::source_code(OUT, &(trs->rdr), trs->wv, cm, col, starts);
    WRITE("|");
    DISCARD_TEXT(cm)
    DISCARD_TEXT(col)

§4.22. Render defn4.22 =

    weave_defn_node *C = RETRIEVE_POINTER_weave_defn_node(N->content);
    WRITE("\\noindent ");
    if (Str::eq(C->keyword, I"enumerate")) WRITE("\\defnannotationtext{enum} ");
    WRITE("\\constantsyntaxcolouring{}|%S|\\plainsyntaxcolouring{} ", C->symbol);
    if (Str::eq(C->keyword, I"default")) WRITE("$\\equiv_{\\hbox\\defnannotationtext{def}}$ ");
    else if (Str::ne(C->keyword, I"enumerate")) WRITE("$\\equiv$ ");
    else WRITE(" ");

§4.23. Commentary and gadget material renderers. Render Markdown4.23 =

    weave_markdown_node *C = RETRIEVE_POINTER_weave_markdown_node(N->content);
    MDRender::render(OUT, &(trs->rdr), C->content);

§4.24. Render carousel slide4.24 =

    weave_carousel_slide_node *C = RETRIEVE_POINTER_weave_carousel_slide_node(N->content);
    TEMPORARY_TEXT(carousel_id)
    TEMPORARY_TEXT(carousel_dots_id)
    LaTeXWeaving::render_carousel_top(OUT, &(trs->rdr), trs->wv, C->slide_number, C->slide_of, carousel_id, carousel_dots_id, C->caption, C->positioning);
    Recurse the renderer through children nodes4.2.1;
    LaTeXWeaving::render_carousel_bottom(OUT, &(trs->rdr), trs->wv, C->slide_number, C->slide_of, carousel_id, carousel_dots_id, C->caption, C->positioning);
    DISCARD_TEXT(carousel_id)
    DISCARD_TEXT(carousel_dots_id)
    return FALSE;

§4.25. TeX itself has an almost defiant lack of support for anything pictorial, which is one reason it didn't live up to its hope of being the definitive basis for typography; even today the loose confederation of TeX-like programs and extensions lack standard approaches. Because of that, we will assume that the pattern has provided suitable macros. All we're trying for is to insert a picture, scaled to a given width, into the text at the current position.

Render figure4.25 =

    weave_figure_node *C = RETRIEVE_POINTER_weave_figure_node(N->content);
    filename *F = Filenames::in(
        Pathnames::down(trs->wv->weave_web->path_to_web, I"Figures"),
        C->figname);
    int w = C->w, h = C->h;
    if ((w <= 0) && (h <= 0)) w = INWEB_POINTS_PER_CM*15;
    if ((w > 0) && (h > 0)) WRITE("\\inwebimagewidthheight{%f}{%d}{%d}\n",
        F, w/INWEB_POINTS_PER_CM, h/INWEB_POINTS_PER_CM);
    else if (w > 0) WRITE("\\inwebimagewidth{%f}{%d}\n", F, w/INWEB_POINTS_PER_CM);
    else if (h > 0) WRITE("\\inwebimageheight{%f}{%d}\n", F, h/INWEB_POINTS_PER_CM);
    else WRITE("\\inwebimage{%f}\n", F);

§4.26. Paragraph tail material renderers. Render index begins4.26 =

    WRITE("\\medskip\n");

§4.27. Render index lemma4.27 =

    WRITE("\\par\\noindent ");
    weave_index_lemma_node *C = RETRIEVE_POINTER_weave_index_lemma_node(N->content);
    ls_index_lemma *lemma = C->lemma;
    for (ls_index_lemma *l2 = lemma->parent; l2; l2 = l2->parent) WRITE("\\quad ");
    if (lemma->style == 2) WRITE("|");
    if (lemma->style == 3) WRITE("/");
    if (lemma->style == 2) WRITE("%S", lemma->text);
    else MDRender::stream(OUT, &(trs->rdr), lemma->text, 0);
    if (lemma->style == 2) WRITE("|");
    if (lemma->style == 3) WRITE("/");
    ls_index_mark *mark; int c = 0;
    LOOP_OVER_LINKED_LIST(mark, ls_index_mark, lemma->marks) {
        if (c++ > 0) WRITE(", "); else WRITE("\\hskip1em ");
        if (mark->important) WRITE("{\\bf ");
        LaTeXWeaving::locale(OUT, &(trs->rdr), mark->at, NULL, trs->current_par);
        if (mark->important) WRITE("}");
    }
    WRITE("\n");

§4.28. Render index ends4.28 =

    WRITE("\n");

§4.29. Render endnote4.29 =

    WRITE("\\par\\noindent\\penalty10000\n");
    WRITE("\\endnotetext{");
    Recurse the renderer through children nodes4.2.1;
    WRITE("}\\smallskip\n");
    return FALSE;

§4.30. Render locale4.30 =

    weave_locale_node *C = RETRIEVE_POINTER_weave_locale_node(N->content);
    LaTeXWeaving::locale(OUT, &(trs->rdr), C->par1, C->par2, trs->current_par);

§4.31. Render endnote text4.31 =

    weave_endnote_text_node *C =
        RETRIEVE_POINTER_weave_endnote_text_node(N->content);
    MDRender::stream(OUT, &(trs->rdr), C->text, 0);

§5. TeX code for headings. 

void LaTeXWeaving::general_heading(text_stream *OUT, markdown_render *rdr, weave_order *wv,
    ls_section *S, ls_paragraph *par, text_stream *heading_text, int weight, int no_skip) {
    text_stream *TeX_macro = NULL;
    Choose which TeX macro to use in order to typeset the new paragraph heading5.1;

    text_stream *orn = (par)?(LiterateSource::par_ornament(par)):I"P";
    text_stream *N = (par)?(par->paragraph_number):NULL;
    TEMPORARY_TEXT(mark)
    Work out the next mark to place into the TeX vertical list5.2;
    TEMPORARY_TEXT(modified)
    MDRender::stream(modified, rdr, heading_text, 0);
    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, modified, U"(%c*?): (%c*)")) {
        Str::clear(modified);
        WRITE_TO(modified, "%S\\quad %S", mr.exp[0], mr.exp[1]);
    }
    if (weight == 2)
        WRITE("\\%S{%S}{%S}{%S}{\\%S}{%S}%%\n",
            TeX_macro, N, modified, mark, orn, NULL);
    else
        WRITE("\\%S{%S}{%S}{%S}{\\%S}{%S}%%\n",
            TeX_macro, N, modified, mark, orn, WebRanges::of(S));
    DISCARD_TEXT(mark)
    DISCARD_TEXT(modified)
    Regexp::dispose_of(&mr);
}

§5.1. We want to have different heading styles for different weights, and TeX is horrible at using macro parameters as function arguments, so we don't want to pass the weight that way. Instead we use

	\weavesection
	\weavesections
	\weavesectionss
	\weavesectionsss

where the weight is the number of terminal ss, 0 to 3. (TeX macros, lamentably, are not allowed digits in their name.) In the cases 0 and 1, we also have variants \nsweavesection and \nsweavesections which are the same, but with the initial vertical spacing removed; these allow us to prevent unsightly excess white space in certain configurations of a section.

Choose which TeX macro to use in order to typeset the new paragraph heading5.1 =

    switch (weight) {
        case 0: TeX_macro = I"weavesection"; break;
        case 1: TeX_macro = I"weavesections"; break;
        case 2: TeX_macro = I"weavesectionss"; break;
        default: TeX_macro = I"weavesectionsss"; break;
    }
    if (Str::len(wv->theme_match) > 0) {
        switch (weight) {
            case 0: TeX_macro = I"tweavesection"; break;
            case 1: TeX_macro = I"tweavesections"; break;
            case 2: TeX_macro = I"tweavesectionss"; break;
            default: TeX_macro = I"tweavesectionsss"; break;
        }
    }
    if (no_skip) {
        switch (weight) {
            case 0: TeX_macro = I"nsweavesection"; break;
            case 1: TeX_macro = I"nsweavesections"; break;
        }
    }

§5.2. "Marks" are the contrivance by which TeX produces running heads on pages which follow the material on those pages: so that the running head for a page can show the paragraph range for the material which tops it, for instance.

The ornament has to be set in math mode, even in the mark. \S and \P, making a section sign and a pilcrow respectively, only work in math mode because they abbreviate characters found in math fonts but not regular ones, in TeX's deeply peculiar font encoding system.

Work out the next mark to place into the TeX vertical list5.2 =

    TEMPORARY_TEXT(chaptermark)
    TEMPORARY_TEXT(sectionmark)
    MDRender::stream(chaptermark, rdr, S->owning_chapter->ch_title, 0);
    if (Str::len(chaptermark) > 0) WRITE_TO(sectionmark, " -- ");
    MDRender::stream(sectionmark, rdr, S->sect_title, 0);
    if (weight < 2)
        WRITE_TO(mark, "%S%S\\quad$\\%S$%S", chaptermark, sectionmark, orn, N);
    else
        WRITE_TO(mark, "%S%S", chaptermark, sectionmark);
    DISCARD_TEXT(chaptermark)
    DISCARD_TEXT(sectionmark)

§6. Holon names. Holon names are highlighted in several cute ways: first, we make use of colour and we drop in the paragraph number of the definition of the macro in small type; and second, we use cross-reference links.

void LaTeXWeaving::holon_name(text_stream *OUT, markdown_render *rdr,
    ls_holon *holon, int defn) {
    ls_paragraph *par = holon->corresponding_chunk->owner;
    if (holon->addendum) par = holon->addendum_to->corresponding_chunk->owner;
    WRITE("$\\langle$");
    if ((defn) && (holon->addendum == FALSE))
        WRITE("\\inwebanchor{para%d}", par->allocation_id + 100);
    else
        WRITE("\\inweblinktopara{para%d}{", par->allocation_id + 100);
    WRITE("\\definitionsyntaxcolouring{}\\holonnametext{");
    MDRender::stream(OUT, rdr, holon->holon_name, 0);
    WRITE("} \\holonnumbertext{%S}", par->paragraph_number);
    WRITE("\\endcolouring{}");
    if (!((defn) && (holon->addendum == FALSE)))
        WRITE("}");
    WRITE("$\\rangle$");
    if (defn) {
        if (holon->addendum) WRITE(" $+${}$\\equiv$");
        else WRITE(" $\\equiv$");
    }
}

§7. Code rendering. Code is typeset by TeX (with our macros) within vertical strokes; these switch a sort of typewriter-type verbatim mode on and off. To get an actual stroke, we must escape from code mode, escape it using a backslash, then re-enter code mode once again:

void LaTeXWeaving::source_code(text_stream *OUT, markdown_render *rdr,
    weave_order *wv, text_stream *matter, text_stream *colouring, int starts) {
    int current_colour = PLAIN_COLOUR, colour_wanted = PLAIN_COLOUR;
    for (int i=0; i < Str::len(matter); i++) {
        colour_wanted = (int) Str::get_at(colouring, i);
        Adjust code colour as necessary7.1;
        if (Str::get_at(matter, i) == '|') WRITE("|\\||");
        else WRITE("%c", Str::get_at(matter, i));
    }
    colour_wanted = PLAIN_COLOUR; Adjust code colour as necessary7.1;
}

§7.1. Adjust code colour as necessary7.1 =

    if (colour_wanted != current_colour) {
        MDRenderLaTeX::change_colour(OUT, rdr, colour_wanted, NULL);
        current_colour = colour_wanted;
    }

§8. Locale links. 

void LaTeXWeaving::locale(OUTPUT_STREAM, markdown_render *rdr, ls_paragraph *par1,
    ls_paragraph *par2, ls_paragraph *from) {
    ls_section *S = LiterateSource::section_of_par(par1);
    ls_section *from_S = LiterateSource::section_of_par(from);
    TEMPORARY_TEXT(nameid)
    LaTeXWeaving::paragraph_link(nameid, par1);
    MDRenderLaTeX::link_internal(OUT, nameid, 0);
    DISCARD_TEXT(nameid)
    if ((S) && (S != from_S)) WRITE("%S:", S->sect_range);
    WRITE("$\\%S$%S", LiterateSource::par_ornament(par1), par1->paragraph_number);
    if (par2) WRITE("-%S", par2->paragraph_number);
    MDRenderLaTeX::end_link(OUT, 0);
}

void LaTeXWeaving::paragraph_link(OUTPUT_STREAM, ls_paragraph *par) {
    ls_section *S = LiterateSource::section_of_par(par);
    WRITE("para");
    if (S)
        for (int i=0; i<Str::len(S->sect_range); i++) {
            inchar32_t c = Str::get_at(S->sect_range, i);
            if (c == '/') WRITE("_");
            else PUT(c);
        }
    WRITE("_%S", par->paragraph_number);
}

§9. Gadgetry. This is convenient when rendering out Markdown which contains images. Note that it actually rewrites the filename, to ensure that the TeX contains a correct file reference to a locally-stored file.

void LaTeXWeaving::notify_image(markdown_render *rdr, text_stream *image) {
    weave_order *wv = RETRIEVE_POINTER_weave_order(rdr->context);
    if (Str::includes_character(image, '/')) return;
    if (Str::includes_character(image, '\\')) return;
    filename *F = Filenames::in(
        Pathnames::down(wv->weave_web->path_to_web, I"Figures"),
        image);
    Str::clear(image);
    WRITE_TO(image, "%f", F);
}

§10. Return TRUE if we have rendered something (or chosen to silently eliminate this gadget from the weave); or FALSE to refuse because the gadget is incomprehensible to us.

int LaTeXWeaving::render_gadget(markdown_render *rdr, OUTPUT_STREAM,
    int gadget, text_stream *text_operand, int w, int h, int mode, text_stream *path) {
    weave_order *wv = RETRIEVE_POINTER_weave_order(rdr->context);

    switch (gadget) {
        case TEXT_AS_INWEBGADGET:
            Render the contents of the named file as code10.1;
            return TRUE;
        case DOWNLOAD_INWEBGADGET:
        case HTML_INWEBGADGET:
        case VIDEO_INWEBGADGET:
        case EMBED_INWEBGADGET:
        case AUDIO_INWEBGADGET:
            return TRUE;
        default:
            return FALSE;
    }
}

§10.1. Render the contents of the named file as code10.1 =

    filename *F = Filenames::from_text_relative(wv->weave_web->path_to_web, path);
    if (TextFiles::exists(F) == FALSE) {
        WRITE_TO(STDERR, "warning: text file at '%S' not found\n", path);
    } else {
        TEMPORARY_TEXT(code)
        TextFiles::write_file_contents(code, F);
        while ((Str::get_last_char(code) == ' ') ||
                (Str::get_last_char(code) == '\t') ||
                (Str::get_last_char(code) == '\n')) Str::delete_last_character(code);
        MDRenderLaTeX::render_code_block(OUT, mode, rdr, code, text_operand);
        DISCARD_TEXT(code)
    }

§11. Carousels. 

int LaTeXWeaving::render_ul_as_carousel(markdown_render *rdr, OUTPUT_STREAM, int mode,
    markdown_item *md) {
    weave_order *wv = RETRIEVE_POINTER_weave_order(rdr->context);
    match_results mr = Regexp::create_mr();
    int count = 1, of = 0;
    for (markdown_item *item = md->down; item; item = item->next) of++;
    for (markdown_item *item = md->down; item; item = item->next) {
        int positioning = 0;
        MDRender::caption(&mr, item, &positioning);
        TEMPORARY_TEXT(carousel_id)
        TEMPORARY_TEXT(carousel_dots_id)
        LaTeXWeaving::render_carousel_top(OUT, rdr, wv, count, of, carousel_id, carousel_dots_id, mr.exp[0], positioning);
        int m = mode | LOOSE_MDRMODE;
        for (markdown_item *c = item->down->next; c; c = c->next) {
            MDRender::render_in_mode(OUT, rdr, c, m);
            m = m & (~EXISTING_PAR_MDRMODE);
        }
        LaTeXWeaving::render_carousel_bottom(OUT, rdr, wv, count, of, carousel_id, carousel_dots_id, mr.exp[0], positioning);
        DISCARD_TEXT(carousel_id)
        DISCARD_TEXT(carousel_dots_id)
        count++;
    }
    Regexp::dispose_of(&mr);
    return TRUE;
}

void LaTeXWeaving::render_carousel_top(OUTPUT_STREAM, markdown_render *rdr, weave_order *wv, int slide_number, int slide_of,
    text_stream *carousel_id, text_stream *carousel_dots_id, text_stream *caption, int positioning) {
    WRITE("\n\\medskip\\hrule\\smallskip\n");
    if (positioning > 0) Place caption here11.1;
}

void LaTeXWeaving::render_carousel_bottom(OUTPUT_STREAM, markdown_render *rdr, weave_order *wv, int slide_number, int slide_of,
    text_stream *carousel_id, text_stream *carousel_dots_id, text_stream *caption, int positioning) {
    if (positioning <= 0) Place caption here11.1;
    WRITE("\n\\smallskip\\hrule\\medskip\n");
}

§11.1. Place caption here11.1 =

    if (Str::len(caption) > 0) {
        WRITE("\\centerline{\\bf %d/%d. ", slide_number, slide_of);
        MDRender::stream(OUT, rdr, caption, 0);
        WRITE("}\n\n");
    }