To provide for weaving into HTML and into EPUB books.

§1. Creation. ePub books are basically mini-websites, so they share the same renderer.

void HTMLWeaving::create(void) {
    Create HTML1.1;
    Create ePub1.2;
}

§1.1. Create HTML1.1 =

    weave_format *wf = WeavingFormats::create_weave_format(I"HTML", I".html");
    METHOD_ADD(wf, RENDER_FOR_MTID, HTMLWeaving::render);

§1.2. Create ePub1.2 =

    weave_format *wf = WeavingFormats::create_weave_format(I"ePub", I".html");
    METHOD_ADD(wf, RENDER_FOR_MTID, HTMLWeaving::render_EPUB);
    METHOD_ADD(wf, BEGIN_WEAVING_FOR_MTID, HTMLWeaving::begin_weaving_EPUB);
    METHOD_ADD(wf, END_WEAVING_FOR_MTID, HTMLWeaving::end_weaving_EPUB);

§2. Rendering. To keep track of what we're writing, we store the renderer state in an instance of this:

classdef HTML_render_state {
    struct text_stream *OUT;
    struct filename *into_file;
    struct weave_order *wv;
    struct colour_scheme *colours;
    int EPUB_flag;
    int popup_counter;
    int slide_number;
    int slide_of;
    struct ls_paragraph *para_to_open;
    struct asset_rule *copy_rule;
} HTML_render_state;

§3. The initial state is as follows:

HTML_render_state HTMLWeaving::initial_state(text_stream *OUT, weave_order *wv,
    int EPUB_mode, filename *into) {
    HTML_render_state hrs;
    hrs.OUT = OUT;
    hrs.into_file = into;
    hrs.wv = wv;
    hrs.EPUB_flag = EPUB_mode;
    hrs.popup_counter = 1;
    hrs.slide_number = -1;
    hrs.slide_of = -1;
    hrs.para_to_open = NULL;
    hrs.copy_rule = Assets::new_rule(NULL, I"", I"privately copy", NULL);

    Swarm::ensure_plugin(wv, I"Base");
    hrs.colours = Swarm::ensure_colour_scheme(wv, I"Colours", I"");

    wv->current_weave_file = into;
    wv->carousel_number = 1;

    return hrs;
}

§4. So, then, here are the front-end method functions for rendering to HTML and ePub respectively:

void HTMLWeaving::render(weave_format *self, text_stream *OUT, heterogeneous_tree *tree) {
    weave_document_node *C = RETRIEVE_POINTER_weave_document_node(tree->root->content);
    HTML::declare_as_HTML(OUT, FALSE);
    HTML_render_state hrs = HTMLWeaving::initial_state(OUT, C->wv, FALSE, C->wv->weave_to);
    Trees::traverse_from(tree->root, &HTMLWeaving::render_visit, (void *) &hrs, 0);
    HTML::completed(OUT);
    if (C->footnotes_present) {
        text_stream *fn_plugin_name = Patterns::get_footnotes_plugin(C->wv->weave_web, C->wv->pattern);
        if (Str::len(fn_plugin_name) > 0)
            Swarm::ensure_plugin(C->wv, fn_plugin_name);
    }
}
void HTMLWeaving::render_EPUB(weave_format *self, text_stream *OUT, heterogeneous_tree *tree) {
    weave_document_node *C = RETRIEVE_POINTER_weave_document_node(tree->root->content);
    HTML::declare_as_HTML(OUT, TRUE);
    HTML_render_state hrs = HTMLWeaving::initial_state(OUT, C->wv, TRUE, C->wv->weave_to);
    Trees::traverse_from(tree->root, &HTMLWeaving::render_visit, (void *) &hrs, 0);
    Epub::note_page(WeavingDetails::get_as_ebook(C->wv->weave_web), C->wv->weave_to, C->wv->booklet_title, I"");
    HTML::completed(OUT);
}

§5. And in either case, we traverse the weave tree with the following visitor function.

int HTMLWeaving::render_visit(tree_node *N, void *state, int L) {
    HTML_render_state *hrs = (HTML_render_state *) state;
    text_stream *OUT = hrs->OUT;
    if ((N->type == weave_document_node_type) ||
        (N->type == weave_body_node_type) ||
        (N->type == weave_chapter_header_node_type) ||
        (N->type == weave_chapter_footer_node_type) ||
        (N->type == weave_pagebreak_node_type) ||
        (N->type == weave_chapter_node_type) ||
        (N->type == weave_chapter_title_page_node_type) ||
        (N->type == weave_grammar_index_node_type)) Render nothing5.45

    else if (N->type == weave_head_node_type) Render head5.1
    else if (N->type == weave_tail_node_type) Render tail5.4
    else if (N->type == weave_verbatim_node_type) Render verbatim5.38
    else if (N->type == weave_section_header_node_type) Render header5.2
    else if (N->type == weave_section_footer_node_type) Render footer5.3
    else if (N->type == weave_section_purpose_node_type) Render purpose5.5
    else if (N->type == weave_subheading_node_type) Render subheading5.6
    else if (N->type == weave_subsubheading_node_type) Render subsubheading5.7
    else if (N->type == weave_bar_node_type) Render bar5.8
    else if (N->type == weave_paragraph_heading_node_type) Render paragraph heading5.9
    else if (N->type == weave_endnote_node_type) Render endnote5.10
    else if (N->type == weave_figure_node_type) Render figure5.11
    else if (N->type == weave_extract_node_type) Render extract5.12
    else if (N->type == weave_audio_node_type) Render audio clip5.13
    else if (N->type == weave_video_node_type) Render video clip5.14
    else if (N->type == weave_download_node_type) Render download5.15
    else if (N->type == weave_material_node_type) Render material5.16
    else if (N->type == weave_embed_node_type) Render embed5.17
    else if (N->type == weave_holon_usage_node_type) Render holon usage5.18
    else if (N->type == weave_tangler_command_node_type) Render tangler command5.19
    else if (N->type == weave_vskip_node_type) Render vskip5.20
    else if (N->type == weave_section_node_type) Render section5.21
    else if (N->type == weave_holon_declaration_node_type) Render holon declaration5.29
    else if (N->type == weave_code_line_node_type) Render code line5.22
    else if (N->type == weave_function_usage_node_type) Render function usage5.23
    else if (N->type == weave_commentary_node_type) Render commentary5.24
    else if (N->type == weave_carousel_slide_node_type) Render carousel slide5.25
    else if (N->type == weave_toc_node_type) Render toc5.26
    else if (N->type == weave_toc_line_node_type) Render toc line5.27
    else if (N->type == weave_defn_node_type) Render defn5.28
    else if (N->type == weave_source_code_node_type) Render source code5.30
    else if (N->type == weave_comment_in_holon_node_type) Render comment in holon5.31
    else if (N->type == weave_url_node_type) Render URL5.32
    else if (N->type == weave_footnote_cue_node_type) Render footnote cue5.33
    else if (N->type == weave_begin_footnote_text_node_type) Render footnote5.34
    else if (N->type == weave_display_line_node_type) Render display line5.35
    else if (N->type == weave_function_defn_node_type) Render function defn5.36
    else if (N->type == weave_item_node_type) Render item5.37
    else if (N->type == weave_inline_node_type) Render inline5.39
    else if (N->type == weave_locale_node_type) Render locale5.40
    else if (N->type == weave_maths_node_type) Render maths5.41
    else if (N->type == weave_markdown_node_type) Render Markdown5.42
    else if (N->type == weave_linebreak_node_type) Render linebreak5.43
    else if (N->type == weave_index_marker_node_type) Render index5.44

    else {
        WRITE_TO(STDERR, "errant node type: %S\n", N->type->node_type_name);
        internal_error("unable to render unknown node");
    }
    return TRUE;
}

§5.1. Render head5.1 =

    weave_head_node *C = RETRIEVE_POINTER_weave_head_node(N->content);
    HTML::comment(OUT, C->banner);

§5.2. Render header5.2 =

    if (hrs->EPUB_flag == FALSE) {
        weave_section_header_node *C =
            RETRIEVE_POINTER_weave_section_header_node(N->content);
        Swarm::ensure_plugin(hrs->wv, I"Breadcrumbs");
        HTML_OPEN_WITH("div", "class=\"breadcrumbs\"");
        HTML_OPEN_WITH("ul", "class=\"crumbs\"");
        Colonies::drop_initial_breadcrumbs(OUT, hrs->wv->weave_colony,
            hrs->wv->weave_to, hrs->wv->breadcrumbs);
        text_stream *bct = Bibliographic::get_datum(hrs->wv->weave_web, I"Title");
        if (Str::len(Bibliographic::get_datum(hrs->wv->weave_web, I"Short Title")) > 0)
            bct = Bibliographic::get_datum(hrs->wv->weave_web, I"Short Title");
        if (hrs->wv->self_contained == FALSE) {
            Colonies::write_breadcrumb(OUT, bct, hrs->wv->home_leaf);
            if (hrs->wv->weave_web->chaptered) {
                TEMPORARY_TEXT(chapter_link)
                WRITE_TO(chapter_link, "%S#%s%S",
                    hrs->wv->home_leaf,
                    (WeavingDetails::get_as_ebook(hrs->wv->weave_web))?"C":"",
                    C->sect->owning_chapter->ch_range);
                Colonies::write_breadcrumb(OUT,
                    C->sect->owning_chapter->ch_title, chapter_link);
                DISCARD_TEXT(chapter_link)
            }
            Colonies::write_breadcrumb(OUT, C->sect->sect_title, NULL);
        } else {
            Colonies::write_breadcrumb(OUT, bct, NULL);
        }
        HTML_CLOSE("ul");
        HTML_CLOSE("div");
    }

§5.3. Render footer5.3 =

    weave_section_footer_node *C =
        RETRIEVE_POINTER_weave_section_footer_node(N->content);
    int count = 0;
    ls_chapter *Ch;
    ls_section *next_S = NULL, *prev_S = NULL, *last = NULL;
    LOOP_OVER_LINKED_LIST(Ch, ls_chapter, hrs->wv->weave_web->chapters) {
        if (Ch->imported == FALSE) {
            ls_section *S;
            LOOP_OVER_LINKED_LIST(S, ls_section, Ch->sections) {
                count ++;
                if (S == C->sect) prev_S = last;
                if (last == C->sect) next_S = S;
                last = S;
            }
        }
    }
    if (count >= 2) {
        HTML_OPEN_WITH("nav", "role=\"progress\"");
        HTML_OPEN_WITH("div", "class=\"progresscontainer\"");
        HTML_OPEN_WITH("ul", "class=\"progressbar\"");
        Insert previous arrow5.3.1;
        ls_chapter *Ch;
        LOOP_OVER_LINKED_LIST(Ch, ls_chapter, hrs->wv->weave_web->chapters) {
            if (Ch->imported == FALSE) {
                if (Str::ne(Ch->ch_range, I"S")) {
                    if (Ch == C->sect->owning_chapter) {
                        HTML_OPEN_WITH("li", "class=\"progresscurrentchapter\"");
                    } else {
                        HTML_OPEN_WITH("li", "class=\"progresschapter\"");
                    }
                    ls_section *S = FIRST_IN_LINKED_LIST(ls_section, Ch->sections);
                    if (S) {
                        TEMPORARY_TEXT(TEMP)
                        Colonies::section_URL(TEMP, S);
                        if (Ch != C->sect->owning_chapter) {
                            HTML::begin_link(OUT, TEMP);
                        }
                        WRITE("%S", Ch->ch_range);
                        if (Ch != C->sect->owning_chapter) {
                            HTML::end_link(OUT);
                        }
                        DISCARD_TEXT(TEMP)
                    }
                    HTML_CLOSE("li");
                }
                if (Ch == C->sect->owning_chapter) {
                    ls_section *S;
                    LOOP_OVER_LINKED_LIST(S, ls_section, Ch->sections) {
                        TEMPORARY_TEXT(label)
                        int on = FALSE;
                        text_stream *range = WebRanges::of(S);
                        LOOP_THROUGH_TEXT(pos, range) {
                            if (Str::get(pos) == '/') on = TRUE;
                            else if (on) PUT_TO(label, Str::get(pos));
                        }
                        if (on == FALSE) Str::copy(label, range);
                        if (Conventions::get_int(hrs->wv->weave_web, SECTIONS_NUMBERED_SEQUENTIALLY_LSCONVENTION))
                            Str::delete_first_character(label);
                        if (S == C->sect) {
                            HTML_OPEN_WITH("li", "class=\"progresscurrent\"");
                            WRITE("%S", label);
                            HTML_CLOSE("li");
                        } else {
                            HTML_OPEN_WITH("li", "class=\"progresssection\"");
                            TEMPORARY_TEXT(TEMP)
                            Colonies::section_URL(TEMP, S);
                            HTML::begin_link(OUT, TEMP);
                            WRITE("%S", label);
                            HTML::end_link(OUT);
                            DISCARD_TEXT(TEMP)
                            HTML_CLOSE("li");
                        }
                        DISCARD_TEXT(label)
                    }
                }
            }
        }
        Insert next arrow5.3.2;
        HTML_CLOSE("ul");
        HTML_CLOSE("div");
        HTML_CLOSE("nav");
    }

§5.3.1. Insert previous arrow5.3.1 =

    if (prev_S) HTML_OPEN_WITH("li", "class=\"progressprev\"")
    else HTML_OPEN_WITH("li", "class=\"progressprevoff\"");
    TEMPORARY_TEXT(TEMP)
    if (prev_S) Colonies::section_URL(TEMP, prev_S);
    if (prev_S) HTML::begin_link(OUT, TEMP);
    WRITE("❮");
    if (prev_S) HTML::end_link(OUT);
    DISCARD_TEXT(TEMP)
    HTML_CLOSE("li");

§5.3.2. Insert next arrow5.3.2 =

    if (next_S) HTML_OPEN_WITH("li", "class=\"progressnext\"")
    else HTML_OPEN_WITH("li", "class=\"progressnextoff\"");
    TEMPORARY_TEXT(TEMP)
    if (next_S) Colonies::section_URL(TEMP, next_S);
    if (next_S) HTML::begin_link(OUT, TEMP);
    WRITE("❯");
    if (next_S) HTML::end_link(OUT);
    DISCARD_TEXT(TEMP)
    HTML_CLOSE("li");

§5.4. Render tail5.4 =

    weave_tail_node *C = RETRIEVE_POINTER_weave_tail_node(N->content);
    HTML::comment(OUT, C->rennab);

§5.5. Render purpose5.5 =

    weave_section_purpose_node *C =
        RETRIEVE_POINTER_weave_section_purpose_node(N->content);
    HTML_OPEN_WITH("p", "class=\"purpose\"");
    HTMLWeaving::escape_text(OUT, C->purpose);
    HTML_CLOSE("p"); WRITE("\n");

§5.6. Render subheading5.6 =

    weave_subheading_node *C = RETRIEVE_POINTER_weave_subheading_node(N->content);
    HTML_OPEN("h3");
    HTMLWeaving::escape_text(OUT, C->text);
    HTML_CLOSE("h3"); WRITE("\n");

§5.7. Render subsubheading5.7 =

    weave_subsubheading_node *C = RETRIEVE_POINTER_weave_subsubheading_node(N->content);
    HTML_OPEN("h4");
    HTMLWeaving::escape_text(OUT, C->text);
    HTML_CLOSE("h4"); WRITE("\n");

§5.8. Render bar5.8 =

    HTML::hr(OUT, NULL);

§5.9. Render paragraph heading5.9 =

    weave_paragraph_heading_node *C =
        RETRIEVE_POINTER_weave_paragraph_heading_node(N->content);
    if (C->para == NULL) internal_error("no para");
    if (N->child == NULL) {
        ls_paragraph *first_in_para = C->para;
        If no para number yet, render a p just to hold this5.9.1;
    }

§5.10. Render endnote5.10 =

    HTML_OPEN("li");
    Recurse the renderer through children nodes5.10.1;
    HTML_CLOSE("li");
    return FALSE;

§5.11. Render figure5.11 =

    weave_figure_node *C = RETRIEVE_POINTER_weave_figure_node(N->content);
    filename *F = Filenames::in(
        Pathnames::down(hrs->wv->weave_web->path_to_web, I"Figures"),
        C->figname);
    filename *RF = Filenames::from_text(C->figname);
    HTML_OPEN_WITH("p", "class=\"center-p\"");
    HTML::image_to_dimensions(OUT, RF, C->alt_text, C->w, C->h);
    Assets::include_asset(OUT, hrs->copy_rule, hrs->wv->weave_web, F, NULL,
        hrs->wv->pattern, hrs->wv->weave_to, hrs->wv->reportage, hrs->wv->weave_colony);
    HTML_CLOSE("p");
    WRITE("\n");

§5.12. Render extract5.12 =

    weave_extract_node *C = RETRIEVE_POINTER_weave_extract_node(N->content);
    HTMLWeaving::render_HTML_extract(OUT, hrs->wv, C->extract);

§5.13. Render audio clip5.13 =

    weave_audio_node *C = RETRIEVE_POINTER_weave_audio_node(N->content);
    HTMLWeaving::render_HTML_player(OUT, hrs->wv, C->audio_name, TRUE, 0, 0);

§5.14. Render video clip5.14 =

    weave_video_node *C = RETRIEVE_POINTER_weave_video_node(N->content);
    HTMLWeaving::render_HTML_player(OUT, hrs->wv, C->video_name, FALSE, C->w, C->h);

§5.15. Render download5.15 =

    weave_download_node *C = RETRIEVE_POINTER_weave_download_node(N->content);
    HTMLWeaving::render_download(OUT, hrs->wv, C->download_name, C->filetype, hrs->into_file);

§5.16. Render material5.16 =

    weave_material_node *C = RETRIEVE_POINTER_weave_material_node(N->content);
    ls_paragraph *first_in_para = NULL;
    if ((N == N->parent->child) &&
        (N->parent->type == weave_paragraph_heading_node_type)) {
        weave_paragraph_heading_node *PC =
            RETRIEVE_POINTER_weave_paragraph_heading_node(N->parent->content);
        first_in_para = PC->para;
    }
    if (C->material_type == COMMENTARY_MATERIAL)
        Deal with a commentary material node5.16.1
    else if (C->material_type == CODE_MATERIAL)
        Deal with a code material node5.16.2
    else if (C->material_type == FOOTNOTES_MATERIAL)
        Deal with a footnotes material node5.16.3
    else if (C->material_type == ENDNOTES_MATERIAL)
        Deal with a endnotes material node5.16.4
    else if (C->material_type == MACRO_MATERIAL)
        Deal with a macro material node5.16.5
    else if (C->material_type == DEFINITION_MATERIAL)
        Deal with a definition material node5.16.6;
    return FALSE;

§5.9.1. If no para number yet, render a p just to hold this5.9.1 =

    if (first_in_para) {
        HTMLWeaving::paragraph_number(OUT, first_in_para);
        HTML_CLOSE("p"); WRITE("\n");
        first_in_para = NULL;
    }

§5.16.1. Deal with a commentary material node5.16.1 =

    int item_depth = 0;
    for (tree_node *M = N->child; M; M = M->next) {
        if (M->type == weave_item_node_type) {
            If no para number yet, render a p just to hold this5.9.1;
            weave_item_node *C = RETRIEVE_POINTER_weave_item_node(M->content);
            HTMLWeaving::go_to_depth(hrs, item_depth, C->depth);
            item_depth = C->depth;
            Trees::traverse_from(M, &HTMLWeaving::render_visit, (void *) hrs, L+1);
            continue;
        }
        if (HTMLWeaving::interior_material(M)) Render a run of interior matter5.16.1.1;
        If no para number yet, render a p just to hold this5.9.1;
        if (item_depth > 0) {
            HTMLWeaving::go_to_depth(hrs, item_depth, 0);
            item_depth = 0;
        }
        if (M->type == weave_vskip_node_type) continue;
        Trees::traverse_from(M, &HTMLWeaving::render_visit, (void *) hrs, L+1);
    }
    if (item_depth > 0) {
        HTMLWeaving::go_to_depth(hrs, item_depth, 0);
        item_depth = 0;
    }

§5.16.1.1. Render a run of interior matter5.16.1.1 =

    int closure_needed = TRUE;
    if (M->type != weave_markdown_node_type) {
        if (first_in_para) {
            HTMLWeaving::paragraph_number(OUT, first_in_para);
            first_in_para = NULL;
        } else {
            if (item_depth == 0) HTML_OPEN_WITH("p", "class=\"commentary\"");
        }
    } else {
        hrs->para_to_open = first_in_para;
        first_in_para = NULL; closure_needed = FALSE;
    }
    while (M) {
        Trees::traverse_from(M, &HTMLWeaving::render_visit, (void *) hrs, L+1);
        if (M->type != weave_markdown_node_type) closure_needed = TRUE;
        if ((M->next == NULL) || (HTMLWeaving::interior_material(M->next) == FALSE)) break;
        M = M->next;
    }
    if ((item_depth == 0) && (closure_needed)) { HTML_CLOSE("p"); WRITE("\n"); }
    continue;

§5.16.2. Deal with a code material node5.16.2 =

    If no para number yet, render a p just to hold this5.9.1;
    if (C->styling) {
        TEMPORARY_TEXT(csname)
        WRITE_TO(csname, "%S-Colours", C->styling->language_name);
        hrs->colours = Swarm::ensure_colour_scheme(hrs->wv,
            csname, C->styling->language_name);
        DISCARD_TEXT(csname)
    }
    TEMPORARY_TEXT(cl)
    WRITE_TO(cl, "%S", hrs->colours->prefix);
    if (C->plainly) WRITE_TO(cl, "undisplayed-code");
    else WRITE_TO(cl, "displayed-code");
    WRITE("<pre class=\"%S all-displayed-code code-font\">\n", cl);
    DISCARD_TEXT(cl)
    Recurse the renderer through children nodes5.10.1;
    HTML_CLOSE("pre"); WRITE("\n");
    if (Str::len(C->endnote) > 0) {
        HTML_OPEN_WITH("ul", "class=\"endnotetexts\"");
        HTML_OPEN("li");
        HTMLWeaving::escape_text(OUT, C->endnote);
        HTML_CLOSE("li");
        HTML_CLOSE("ul"); WRITE("\n");
    }

§5.16.3. Deal with a footnotes material node5.16.3 =

    If no para number yet, render a p just to hold this5.9.1;
    HTML_OPEN_WITH("ul", "class=\"footnotetexts\"");
    Recurse the renderer through children nodes5.10.1;
    HTML_CLOSE("ul"); WRITE("\n");

§5.16.4. Deal with a endnotes material node5.16.4 =

    If no para number yet, render a p just to hold this5.9.1;
    HTML_OPEN_WITH("ul", "class=\"endnotetexts\"");
    Recurse the renderer through children nodes5.10.1;
    HTML_CLOSE("ul"); WRITE("\n");

§5.16.5. Deal with a macro material node5.16.5 =

    if (first_in_para) {
        HTMLWeaving::paragraph_number(OUT, first_in_para);
    } else {
        HTML_OPEN_WITH("p", "class=\"commentary\"");
    }
    Recurse the renderer through children nodes5.10.1;
    HTML_CLOSE("p"); WRITE("\n");

§5.16.6. Deal with a definition material node5.16.6 =

    If no para number yet, render a p just to hold this5.9.1;
    HTML_OPEN_WITH("pre", "class=\"definitions code-font\"");
    Recurse the renderer through children nodes5.10.1;
    HTML_CLOSE("pre"); WRITE("\n");

§5.17. This has to embed some Internet-sourced content. service here is something like YouTube or Soundcloud, and ID is whatever code that service uses to identify the video/audio in question.

Render embed5.17 =

    weave_embed_node *C = RETRIEVE_POINTER_weave_embed_node(N->content);
    HTMLWeaving::render_embedding(OUT, hrs->wv, C->ID, C->service, C->w, C->h, hrs->into_file);

§5.18. Render holon usage5.18 =

    weave_holon_usage_node *C = RETRIEVE_POINTER_weave_holon_usage_node(N->content);
    HTML_OPEN_WITH("span", "class=\"named-paragraph-container code-font\"");
    TEMPORARY_TEXT(url)
    Colonies::paragraph_URL(url, C->holon->corresponding_chunk->owner, hrs->wv->weave_to, hrs->wv->weave_colony);
    HTML::begin_link_with_class(OUT, I"named-paragraph-link", url);
    DISCARD_TEXT(url)
    HTML_OPEN_WITH("span", "class=\"named-paragraph\"");
    ls_holon *holon = C->holon;
    if (holon) {
        if (holon->holon_name_as_markdown) {
            HTML_OPEN_WITH("span", "class=\"mathjax_process\"");
            MDRenderer::render_extended(OUT, (void *) hrs->wv, holon->holon_name_as_markdown, C->variation, 0);
            HTML_CLOSE("span");
        } else
            HTMLWeaving::escape_text(OUT, holon->holon_name);
    }
    HTML_CLOSE("span");
    HTML_OPEN_WITH("span", "class=\"named-paragraph-number\"");
    HTMLWeaving::escape_text(OUT, C->holon->corresponding_chunk->owner->paragraph_number);
    HTML_CLOSE("span");
    HTML::end_link(OUT);
    HTML_CLOSE("span");

§5.19. Render tangler command5.19 =

    weave_tangler_command_node *C = RETRIEVE_POINTER_weave_tangler_command_node(N->content);
    HTML_OPEN_WITH("span", "class=\"named-paragraph-container code-font\"");
    HTML_OPEN_WITH("span", "class=\"named-paragraph\"");
    HTMLWeaving::escape_text(OUT, I"output from tangler command '");
    HTMLWeaving::escape_text(OUT, C->command);
    HTMLWeaving::escape_text(OUT, I"'");
    HTML_CLOSE("span");
    HTML_CLOSE("span");

§5.20. Render vskip5.20 =

    WRITE("\n");

§5.21. Render section5.21 =

    weave_section_node *C = RETRIEVE_POINTER_weave_section_node(N->content);
    LOG("It was %d\n", C->allocation_id);

§5.22. Render code line5.22 =

    Recurse the renderer through children nodes5.10.1;
    WRITE("\n");
    return FALSE;

§5.23. Render function usage5.23 =

    weave_function_usage_node *C = RETRIEVE_POINTER_weave_function_usage_node(N->content);
    HTML::begin_link_with_class(OUT, I"function-link", C->url);
    HTMLWeaving::change_colour(OUT, FUNCTION_COLOUR, hrs->colours);
    WRITE("%S", C->fn->function_name);
    HTMLWeaving::change_colour(OUT, -1, hrs->colours);
    HTML::end_link(OUT);

§5.24. Render commentary5.24 =

    weave_commentary_node *C = RETRIEVE_POINTER_weave_commentary_node(N->content);
    if (C->in_code) HTMLWeaving::change_colour(OUT, COMMENT_COLOUR, hrs->colours);
    for (int i=0; i < Str::len(C->text); i++) {
        if (Str::get_at(C->text, i) == '&') WRITE("&amp;");
        else if (Str::get_at(C->text, i) == '<') WRITE("&lt;");
        else if (Str::get_at(C->text, i) == '>') WRITE("&gt;");
        else if ((i == 0) && (Str::get_at(C->text, i) == '-') &&
            (Str::get_at(C->text, i+1) == '-') &&
            ((Str::get_at(C->text, i+2) == ' ') || (Str::get_at(C->text, i+2) == 0))) {
            WRITE("&mdash;"); i++;
        } else if ((Str::get_at(C->text, i) == ' ') && (Str::get_at(C->text, i+1) == '-') &&
            (Str::get_at(C->text, i+2) == '-') &&
            ((Str::get_at(C->text, i+3) == ' ') || (Str::get_at(C->text, i+3) == '\n') ||
            (Str::get_at(C->text, i+3) == 0))) {
            WRITE(" &mdash;"); i+=2;
        } else PUT(Str::get_at(C->text, i));
    }
    if (C->in_code) HTMLWeaving::change_colour(OUT, -1, hrs->colours);

§5.25. Render carousel slide5.25 =

    weave_carousel_slide_node *C = RETRIEVE_POINTER_weave_carousel_slide_node(N->content);
    if (hrs->slide_number == -1) {
        hrs->slide_number = 1;
        hrs->slide_of = 0;
        for (tree_node *X = N; (X) && (X->type == N->type); X = X->next) hrs->slide_of++;
    } else {
        hrs->slide_number++;
        if (hrs->slide_number > hrs->slide_of) internal_error("miscounted slides");
    }
    TEMPORARY_TEXT(carousel_id)
    TEMPORARY_TEXT(carousel_dots_id)
    HTMLWeaving::render_carousel_top(OUT, hrs->wv, hrs->slide_number, hrs->slide_of, carousel_id, carousel_dots_id, C->caption, C->positioning);
    Recurse the renderer through children nodes5.10.1;
    HTMLWeaving::render_carousel_bottom(OUT, hrs->wv, hrs->slide_number, hrs->slide_of, carousel_id, carousel_dots_id, C->caption, C->positioning);
    DISCARD_TEXT(carousel_id)
    DISCARD_TEXT(carousel_dots_id)
    if (hrs->slide_number == hrs->slide_of) {
        hrs->slide_number = -1;
        hrs->slide_of = -1;
    }
    return FALSE;

§5.26. Render toc5.26 =

    HTML_OPEN_WITH("ul", "class=\"toc\"");
    for (tree_node *M = N->child; M; M = M->next) {
        HTML_OPEN("li");
        Trees::traverse_from(M, &HTMLWeaving::render_visit, (void *) hrs, L+1);
        HTML_CLOSE("li");
    }
    HTML_CLOSE("ul");
    HTML::hr(OUT, "tocbar");
    WRITE("\n");
    return FALSE;

§5.27. Render toc line5.27 =

    weave_toc_line_node *C = RETRIEVE_POINTER_weave_toc_line_node(N->content);
    TEMPORARY_TEXT(TEMP)
    Colonies::paragraph_URL(TEMP, C->para, hrs->wv->weave_to, hrs->wv->weave_colony);
    HTML::begin_link(OUT, TEMP);
    DISCARD_TEXT(TEMP)
    int depth = LiterateSource::par_depth(C->para);
    if (depth == -1) HTML_OPEN("b");
    if (depth > 0) HTML_OPEN("i");
    WRITE("%s%S", (Str::get_first_char(LiterateSource::par_ornament(C->para)) == 'S')?"&#167;":"&para;",
        C->para->paragraph_number);
    WRITE(". ");
    HTMLWeaving::escape_text(OUT, C->text2);
    if (depth > 0) HTML_CLOSE("i");
    if (depth == -1) HTML_CLOSE("b");
    HTML::end_link(OUT);

§5.28. Render defn5.28 =

    weave_defn_node *C = RETRIEVE_POINTER_weave_defn_node(N->content);
    HTML_OPEN_WITH("span", "class=\"definition-keyword\"");
    WRITE("%S", C->keyword);
    HTML_CLOSE("span");
    WRITE(" ");
    if (Str::len(C->symbol) > 0) {
        HTML_OPEN_WITH("span", "class=\"identifier-syntax\"");
        WRITE("%S", C->symbol);
        HTML_CLOSE("span");
        WRITE(" ");
    }

§5.29. Render holon declaration5.29 =

    weave_holon_declaration_node *C = RETRIEVE_POINTER_weave_holon_declaration_node(N->content);
    HTML_OPEN_WITH("span", "class=\"named-paragraph-container code-font\"");
    ls_holon *label_holon = C->holon;
    if (C->holon->addendum_to) {
        label_holon = C->holon->addendum_to;
        TEMPORARY_TEXT(url)
        Colonies::paragraph_URL(url, label_holon->corresponding_chunk->owner, hrs->wv->weave_to, hrs->wv->weave_colony);
        HTML::begin_link_with_class(OUT, I"named-paragraph-link", url);
        DISCARD_TEXT(url)
    }
    HTML_OPEN_WITH("span", "class=\"named-paragraph-defn\"");
    if (label_holon->file_form) { PUT(0x2192); PUT(0x0020); }
    if (label_holon->holon_name_as_markdown)
        MDRenderer::render_extended(OUT, (void *) hrs->wv, label_holon->holon_name_as_markdown, C->variation, 0);
    else
        HTMLWeaving::escape_text(OUT, label_holon->holon_name);
    HTML_CLOSE("span");
    HTML_OPEN_WITH("span", "class=\"named-paragraph-number\"");
    HTMLWeaving::escape_text(OUT, label_holon->corresponding_chunk->owner->paragraph_number);
    HTML_CLOSE("span");
    if (C->holon->addendum_to) HTML::end_link(OUT);
    HTML_CLOSE("span");
    if (C->holon->addendum_to) HTMLWeaving::escape_text(OUT, I" +=");
    else HTMLWeaving::escape_text(OUT, I" =");

§5.30. Render source code5.30 =

    weave_source_code_node *C = RETRIEVE_POINTER_weave_source_code_node(N->content);
    HTMLWeaving::render_syntax_coloured(OUT, C->matter, C->colouring, hrs->colours);

§5.31. Render comment in holon5.31 =

    weave_comment_in_holon_node *C = RETRIEVE_POINTER_weave_comment_in_holon_node(N->content);
    if (C->as_markdown) {
        HTML_OPEN_WITH("span", "class=\"comment-syntax\"");
        HTMLWeaving::escape_text(OUT, C->comment_open);
        for (int i=0; ((i<Str::len(C->raw)) && (Characters::is_whitespace(Str::get_at(C->raw, i)))); i++)
            PUT(Str::get_at(C->raw, i));
        MDRenderer::render_extended(OUT, (void *) hrs->wv, C->as_markdown, C->variation, 0);
        for (int i=Str::len(C->raw) - 1; ((i>=0) && (Characters::is_whitespace(Str::get_at(C->raw, i)))); i--)
            PUT(Str::get_at(C->raw, i));
        HTMLWeaving::escape_text(OUT, C->comment_close);
        HTML_CLOSE("span");
    } else
        WRITE("NO-MARKDOWN-AVAILABLE");

§5.32. Render URL5.32 =

    weave_url_node *C = RETRIEVE_POINTER_weave_url_node(N->content);
    HTML::begin_link_with_class(OUT, (C->external)?I"external":I"internal", C->url);
    WRITE("%S", C->content);
    HTML::end_link(OUT);

§5.33. Render footnote cue5.33 =

    weave_footnote_cue_node *C = RETRIEVE_POINTER_weave_footnote_cue_node(N->content);
    if (hrs->EPUB_flag) {
        if (N->parent->type != weave_begin_footnote_text_node_type)
            WRITE("<a id=\"fnref%S\"></a>", C->cue_text);
        WRITE("<sup><a href=\"#fn%S\" rel=\"footnote\">%S</a></sup>",
            C->cue_text, C->cue_text);
    } else
        WRITE("<sup id=\"fnref:%S\"><a href=\"#fn:%S\" rel=\"footnote\">%S</a></sup>",
            C->cue_text, C->cue_text, C->cue_text);

§5.34. Render footnote5.34 =

    weave_begin_footnote_text_node *C =
        RETRIEVE_POINTER_weave_begin_footnote_text_node(N->content);
    if (hrs->EPUB_flag)
        WRITE("<li class=\"footnote\" id=\"fn%S\"><p class=\"inwebfootnote\">",
            C->cue_text);
    else
        WRITE("<li class=\"footnote\" id=\"fn:%S\"><p class=\"inwebfootnote\">",
            C->cue_text);
    Recurse the renderer through children nodes5.10.1;
    if (hrs->EPUB_flag)
        WRITE("<a href=\"#fnref%S\"> (return to text)</a></p></li>",
            C->cue_text);
    else
        WRITE("<a href=\"#fnref:%S\" title=\"return to text\"> &#x21A9;</a></p></li>",
            C->cue_text);
    return FALSE;

§5.35. Render display line5.35 =

    weave_display_line_node *C =
        RETRIEVE_POINTER_weave_display_line_node(N->content);
    HTML_OPEN("blockquote"); WRITE("\n"); INDENT;
    HTML_OPEN("p");
    HTMLWeaving::escape_text(OUT, C->text);
    HTML_CLOSE("p");
    OUTDENT; HTML_CLOSE("blockquote"); WRITE("\n");

§5.36. Render function defn5.36 =

    weave_function_defn_node *C =
        RETRIEVE_POINTER_weave_function_defn_node(N->content);
    if ((Functions::used_elsewhere(C->fn)) && (hrs->EPUB_flag == FALSE)) {
        Swarm::ensure_plugin(hrs->wv, I"Popups");
        HTMLWeaving::change_colour(OUT, FUNCTION_COLOUR, hrs->colours);
        WRITE("%S", C->fn->function_name);
        WRITE("</span>");
        WRITE("<button class=\"popup\" onclick=\"togglePopup('usagePopup%d')\">",
            hrs->popup_counter);
        HTMLWeaving::change_colour(OUT, COMMENT_COLOUR, hrs->colours);
        WRITE("?");
        HTMLWeaving::change_colour(OUT, -1, hrs->colours);
        WRITE("<span class=\"popuptext\" id=\"usagePopup%d\">Usage of ", hrs->popup_counter);
        HTML_OPEN_WITH("span", "class=\"code-font\"");
        HTMLWeaving::change_colour(OUT, FUNCTION_COLOUR, hrs->colours);
        WRITE("%S", C->fn->function_name);
        HTMLWeaving::change_colour(OUT, -1, hrs->colours);
        HTML_CLOSE("span");
        WRITE(":<br/>");
        Recurse the renderer through children nodes5.10.1;
        HTMLWeaving::change_colour(OUT, -1, hrs->colours);
        WRITE("</button>");
        hrs->popup_counter++;
    } else {
        HTMLWeaving::change_colour(OUT, FUNCTION_COLOUR, hrs->colours);
        WRITE("%S", C->fn->function_name);
        HTMLWeaving::change_colour(OUT, -1, hrs->colours);
    }
    return FALSE;

§5.37. Render item5.37 =

    weave_item_node *C = RETRIEVE_POINTER_weave_item_node(N->content);
    if (Str::eq(C->label, I"*")) WRITE("&#9679; ");
    else if (Str::len(C->label) > 0) WRITE("(%S) ", C->label);
    else WRITE(" ");

§5.38. Render verbatim5.38 =

    weave_verbatim_node *C = RETRIEVE_POINTER_weave_verbatim_node(N->content);
    WRITE("%S", C->content);

§5.39. Render inline5.39 =

    HTML_OPEN_WITH("span", "class=\"extract\"");
    Recurse the renderer through children nodes5.10.1;
    HTML_CLOSE("span");
    return FALSE;

§5.40. Render locale5.40 =

    weave_locale_node *C = RETRIEVE_POINTER_weave_locale_node(N->content);
    TEMPORARY_TEXT(TEMP)
    Colonies::paragraph_URL(TEMP, C->par1, hrs->wv->weave_to, hrs->wv->weave_colony);
    HTML::begin_link(OUT, TEMP);
    DISCARD_TEXT(TEMP)
    if (C->distant) {
        if (C->par1->owning_unit->owning_section)
            WRITE("%S:", C->par1->owning_unit->owning_section->sect_range);
        else
            WRITE("external:");
    }
    WRITE("%s%S",
        (Str::get_first_char(LiterateSource::par_ornament(C->par1)) == 'S')?"&#167;":"&para;",
        C->par1->paragraph_number);
    if (C->par2) WRITE("-%S", C->par2->paragraph_number);
    HTML::end_link(OUT);

§5.41. Render maths5.41 =

    weave_maths_node *C = RETRIEVE_POINTER_weave_maths_node(N->content);
    HTMLWeaving::render_maths(OUT, hrs->wv, C->content, hrs->EPUB_flag, C->displayed);

§5.42. Render Markdown5.42 =

    ls_paragraph *first_in_para = NULL;
    if ((N == N->parent->child) &&
        (N->parent->type == weave_paragraph_heading_node_type)) {
        weave_paragraph_heading_node *PC =
            RETRIEVE_POINTER_weave_paragraph_heading_node(N->parent->content);
        first_in_para = PC->para;
    }
    HTML_OPEN_WITH("div", "class=\"lsmarkdown\"");
    OUTDENT;
    int mode = 0;
    weave_markdown_node *C = RETRIEVE_POINTER_weave_markdown_node(N->content);
    if ((first_in_para) || (hrs->para_to_open)) {
        if (hrs->para_to_open) HTMLWeaving::paragraph_number(OUT, hrs->para_to_open);
        else HTMLWeaving::paragraph_number(OUT, first_in_para);
        hrs->para_to_open = NULL;
        if ((C->content) && (C->content->down) && (C->content->down->type == PARAGRAPH_MIT)) {
            mode = EXISTING_PAR_MDRMODE;
            WRITE(" ");
        } else {
            HTML_CLOSE("p");
        }
    }
    MDRenderer::render_extended(OUT, (void *) hrs->wv, C->content, C->variation, mode);
    INDENT;
    HTML_CLOSE("div");

§5.43. Render linebreak5.43 =

    WRITE("<br/>");

§5.44. Render index5.44 =

    HTML_OPEN_WITH("div", "class=\"lsindex\"");
    if ((hrs->wv) && (hrs->wv->weave_web)) {
        ls_index *index = hrs->wv->weave_web->index;
        if (index->lemmas_sorted == NULL) WebIndexing::sort(index, I"0");
        if (index->lemmas_sorted)
            for (int i=0; i<(int) (index->no_lemmas_sorted); i++) {
                ls_index_lemma *lemma = index->lemmas_sorted[i];
                int d = 0;
                for (ls_index_lemma *l2 = lemma->parent; l2; l2 = l2->parent) d++;
                text_stream *pclass = I"lsindexlemma";
                if (d == 1) pclass = I"lsindexsublemma";
                if (d == 2) pclass = I"lsindexsubsublemma";
                if (d >= 3) pclass = I"lsindexsubsubsublemma";
                HTML_OPEN_WITH("p", "class=\"%S\"", pclass);
                switch (lemma->style) {
                    case 1: HTML_OPEN_WITH("span", "class=\"lsindextext\""); break;
                    case 2: HTML_OPEN_WITH("span", "class=\"lsindextexttt\""); break;
                    case 3: HTML_OPEN_WITH("span", "class=\"lsindextextns\""); break;
                }
                HTMLWeaving::escape_text(OUT, lemma->text);
                HTML_CLOSE("span");
                ls_index_mark *mark; int c = 0;
                LOOP_OVER_LINKED_LIST(mark, ls_index_mark, lemma->marks) {
                    if (c++ > 0) WRITE(", "); else WRITE("&nbsp;&nbsp;");
                    if (mark->important) HTML_OPEN("b");
                    HTMLWeaving::escape_text(OUT, mark->at->paragraph_number);
                    if (mark->important) HTML_CLOSE("b");
                }
                HTML_CLOSE("p");
            }
    }
    HTML_CLOSE("div");

§5.45. Render nothing5.45 =

    ;

§5.10.1. Recurse the renderer through children nodes5.10.1 =

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

§6. This is convenient when rendering out Markdown which contains images:

void HTMLWeaving::notify_image(weave_order *wv, text_stream *image) {
    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);
    Assets::include_asset(NULL, Assets::new_rule(NULL, I"", I"privately copy", NULL),
        wv->weave_web, F, NULL,
        wv->pattern, wv->weave_to, wv->reportage, wv->weave_colony);
}

§7. The necessary escapes for the use of the MathJax plugin.

void HTMLWeaving::render_maths(OUTPUT_STREAM, weave_order *wv, text_stream *content,
    int plain, int displayed) {
    text_stream *plugin_name = (wv)?(Patterns::get_mathematics_plugin(wv->weave_web, wv->pattern)):NULL;
    if ((Str::len(plugin_name) == 0) || (plain)) {
        TEMPORARY_TEXT(R)
        TeXUtilities::remove_math_mode(R, content);
        HTMLWeaving::escape_text(OUT, R);
        DISCARD_TEXT(R)
    } else {
        Swarm::ensure_plugin(wv, plugin_name);
        if (displayed) WRITE("$$"); else WRITE("\\INWEBMATH(");
        TEMPORARY_TEXT(escaped)
        HTMLWeaving::escape_text(escaped, content);
        for (int i=0; i<Str::len(escaped); i++) {
            if (Str::get_at(escaped, i) == '|') {
                int found = FALSE;
                for (int j=i+1; j<Str::len(escaped); j++) {
                    if (Str::get_at(escaped, j) == '|') {
                        WRITE("\\hbox{\\tt ");
                        for (int k=i+1; k<j; k++) PUT(Str::get_at(escaped, k));
                        WRITE("}");
                        i = j;
                        found = TRUE; break;
                    }
                }
                if (found == FALSE) PUT(Str::get_at(escaped, i));
            } else {
                PUT(Str::get_at(escaped, i));
            }
        }
        DISCARD_TEXT(escaped)
        if (displayed) WRITE("$$"); else WRITE("\\INWEBMATH)");
    }
}

§8. These are the nodes falling under a commentary material node which we will amalgamate into a single HTML paragraph:

int HTMLWeaving::interior_material(tree_node *N) {
    if (N->type == weave_commentary_node_type) return TRUE;
    if (N->type == weave_markdown_node_type) return TRUE;
    if (N->type == weave_url_node_type) return TRUE;
    if (N->type == weave_inline_node_type) return TRUE;
    if (N->type == weave_locale_node_type) return TRUE;
    if (N->type == weave_maths_node_type) return TRUE;
    if (N->type == weave_footnote_cue_node_type) return TRUE;
    return FALSE;
}

§9. Depth 1 means "inside a list entry"; depth 2, "inside an entry of a list which is itself inside a list entry"; and so on.

void HTMLWeaving::go_to_depth(HTML_render_state *hrs, int from_depth, int to_depth) {
    text_stream *OUT = hrs->OUT;
    if (from_depth == to_depth) {
        HTML_CLOSE("li");
    } else {
        while (from_depth < to_depth) {
            HTML_OPEN_WITH("ul", "class=\"items\""); from_depth++;
        }
        while (from_depth > to_depth) {
            HTML_CLOSE("li");
            HTML_CLOSE("ul");
            WRITE("\n"); from_depth--;
        }
    }
    if (to_depth > 0) HTML_OPEN("li");
}

§10. 

void HTMLWeaving::paragraph_number(text_stream *OUT, ls_paragraph *par) {
    text_stream *title = LiterateSource::par_title(par);
    int depth = LiterateSource::par_depth(par);
    if (depth == -1) {
        HTML_OPEN("h2");
        HTMLWeaving::escape_text(OUT, title);
        HTML_CLOSE("h2");
    }
    HTML_OPEN_WITH("p", "class=\"commentary firstcommentary\"");
    TEMPORARY_TEXT(TEMP)
    Colonies::paragraph_anchor(TEMP, par);
    HTML::anchor_with_class(OUT, TEMP, I"paragraph-anchor");
    DISCARD_TEXT(TEMP)
    if (LiterateSource::par_has_visible_number(par)) {
        HTML_OPEN("b");
        WRITE("%s%S", (Str::get_first_char(LiterateSource::par_ornament(par)) == 'S')?"&#167;":"&para;",
            par->paragraph_number);
        WRITE(". ");
        HTMLWeaving::escape_text(OUT, title);
        if (Str::len(title) > 0) WRITE(".");
        HTML_CLOSE("b");
        WRITE(" ");
    }
}

§11. 

void HTMLWeaving::change_colour(text_stream *OUT, int col, colour_scheme *cs) {
    if (col == -1) {
        HTML_CLOSE("span");
    } else {
        text_stream *cl = Painter::colour_classname(NULL, (inchar32_t) col);
        if (Str::len(cl) == 0) {
            PRINT("col: %d\n", col); internal_error("bad colour");
        } else {
            HTML_OPEN_WITH("span", "class=\"%S%S\"", cs->prefix, cl);
        }
    }
}

§12. 

void HTMLWeaving::escape_text(text_stream *OUT, text_stream *id) {
    for (int i=0; i < Str::len(id); i++) {
        if (Str::get_at(id, i) == '&') WRITE("&amp;");
        else if (Str::get_at(id, i) == '<') WRITE("&lt;");
        else if (Str::get_at(id, i) == '>') WRITE("&gt;");
        else PUT(Str::get_at(id, i));
    }
}

§13. 

void HTMLWeaving::render_code_block(OUTPUT_STREAM, int mode, weave_order *wv, text_stream *code, text_stream *language_rendered) {
    TEMPORARY_TEXT(name)
    WRITE_TO(name, "%S-Colours", language_rendered);
    colour_scheme *colours = Assets::find_colour_scheme(wv->weave_web, wv->pattern,
        name, language_rendered);
    text_stream *prefix = language_rendered;
    if (colours) Swarm::ensure_colour_scheme(wv, name, language_rendered);
    if (colours == NULL) {
        colours = Assets::find_colour_scheme(wv->weave_web, wv->pattern, I"Colours", I"");
        prefix = NULL;
    }
    if (colours == NULL) internal_error("no colour scheme available");
    DISCARD_TEXT(name)

    if (Str::len(prefix) > 0) {
        if (mode & TAGS_MDRMODE)
            HTML_OPEN_WITH("pre", "class=\"%S-displayed-code all-displayed-code code-font\"",
                prefix);
    } else {
        if (mode & TAGS_MDRMODE)
            HTML_OPEN_WITH("pre", "class=\"displayed-code all-displayed-code code-font\"");
    }

    TEMPORARY_TEXT(colouring)
    programming_language *pl = wv->weave_web->web_language;
    if (Str::len(language_rendered) > 0)
        pl = Languages::find(wv->weave_web, language_rendered);
    if (pl == NULL) {
        WRITE_TO(STDERR, "warning: no language definition for '%S'\n", language_rendered);
        pl = Languages::find(wv->weave_web, I"None");
    }
    Painter::reset_syntax_colouring(pl);
    TEMPORARY_TEXT(line)
    TEMPORARY_TEXT(cols)
    int i = 0;
    while (i < Str::len(code)) {
        inchar32_t c = Str::get_at(code, i);
        if ((c == '\n') || (i+1 == Str::len(code))) {
            if (c != '\n') PUT_TO(line, c);
            Painter::syntax_colour(pl, &(pl->built_in_keywords), line, cols, FALSE, TRUE);
            Str::clear(line);
            WRITE_TO(colouring, "%S%c", cols, PLAIN_COLOUR);
            Str::clear(cols);
        } else {
            PUT_TO(line, c);
        }
        i++;
    }
    DISCARD_TEXT(line)
    DISCARD_TEXT(cols)
    HTMLWeaving::render_syntax_coloured(OUT, code, colouring, colours);
    DISCARD_TEXT(colouring)
    if (mode & TAGS_MDRMODE) HTML_CLOSE("pre");
    WRITE("\n");
}

void HTMLWeaving::render_syntax_coloured(OUTPUT_STREAM, text_stream *code,
    text_stream *colouring, colour_scheme *colours) {
    int current_colour = -1, colour_wanted = PLAIN_COLOUR;
    for (int i=0; i < Str::len(code); i++) {
        colour_wanted = (int) Str::get_at(colouring, i);
        if (colour_wanted != current_colour) {
            if (current_colour >= 0) HTML_CLOSE("span");
            HTMLWeaving::change_colour(OUT, colour_wanted, colours);
            current_colour = colour_wanted;
        }
        if (Str::get_at(code, i) == '<') WRITE("&lt;");
        else if (Str::get_at(code, i) == '>') WRITE("&gt;");
        else if (Str::get_at(code, i) == '&') WRITE("&amp;");
        else WRITE("%c", Str::get_at(code, i));
    }
    if (current_colour >= 0) HTMLWeaving::change_colour(OUT, -1, colours);
}

int HTMLWeaving::render_text_as_image(OUTPUT_STREAM, int mode, weave_order *wv,
    text_stream *desc, text_stream *path) {
    match_results mr = Regexp::create_mr();
    text_stream *as = NULL;
    if (Regexp::match(&mr, desc, U"text as (%c+)")) as = mr.exp[0];
    if (Str::eq(desc, I"text")) as = I"None";
    if (as) {
        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);
            HTMLWeaving::render_code_block(OUT, mode, wv, code, as);
            DISCARD_TEXT(code)
        }
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if (Regexp::match(&mr, desc, U"download: (%c+)")) {
        HTMLWeaving::render_download(OUT, wv, path, mr.exp[0], wv->current_weave_file);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if (Str::eq_insensitive(desc, I"HTML")) {
        HTMLWeaving::render_HTML_extract(OUT, wv, path);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if (Str::eq(desc, I"video")) {
        HTMLWeaving::render_HTML_player(OUT, wv, path, FALSE, 0, 0);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if (Regexp::match(&mr, desc, U"video at (%d+) by (%d+)")) {
        int w = Str::atoi(mr.exp[0], 0), h = Str::atoi(mr.exp[1], 0);
        HTMLWeaving::render_HTML_player(OUT, wv, path, FALSE, w, h);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if (Regexp::match(&mr, desc, U"video at width (%d+)")) {
        int w = Str::atoi(mr.exp[0], 0);
        HTMLWeaving::render_HTML_player(OUT, wv, path, FALSE, w, 0);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if (Regexp::match(&mr, desc, U"video at height (%d+)")) {
        int h = Str::atoi(mr.exp[0], 0);
        HTMLWeaving::render_HTML_player(OUT, wv, path, FALSE, 0, h);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if ((Regexp::match(&mr, desc, U"embedded (%c+) audio")) ||
        (Regexp::match(&mr, desc, U"embedded (%c+) video"))) {
        HTMLWeaving::render_embedding(OUT, wv, path, mr.exp[0], 0, 0, wv->current_weave_file);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if ((Regexp::match(&mr, desc, U"embedded (%c+) audio at (%d+) by (%d+)")) ||
        (Regexp::match(&mr, desc, U"embedded (%c+) video at (%d+) by (%d+)"))) {
        int w = Str::atoi(mr.exp[1], 0), h = Str::atoi(mr.exp[2], 0);
        HTMLWeaving::render_embedding(OUT, wv, path, mr.exp[0], w, h, wv->current_weave_file);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if ((Regexp::match(&mr, desc, U"embedded (%c+) audio at height (%d+)")) ||
        (Regexp::match(&mr, desc, U"embedded (%c+) video at height (%d+)"))) {
        int w = 0, h = Str::atoi(mr.exp[1], 0);
        HTMLWeaving::render_embedding(OUT, wv, path, mr.exp[0], w, h, wv->current_weave_file);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if ((Regexp::match(&mr, desc, U"embedded (%c+) audio at width (%d+)")) ||
        (Regexp::match(&mr, desc, U"embedded (%c+) video at width (%d+)"))) {
        int w = Str::atoi(mr.exp[1], 0), h = 0;
        HTMLWeaving::render_embedding(OUT, wv, path, mr.exp[0], w, h, wv->current_weave_file);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    if (Str::eq(desc, I"audio")) {
        HTMLWeaving::render_HTML_player(OUT, wv, path, TRUE, 0, 0);
        Regexp::dispose_of(&mr);
        return TRUE;
    }
    Regexp::dispose_of(&mr);
    return FALSE;
}

void HTMLWeaving::render_download(OUTPUT_STREAM, weave_order *wv, text_stream *download_name,
    text_stream *filetype, filename *into_file) {
    pathname *P = Pathnames::down(wv->weave_web->path_to_web, I"Downloads");
    filename *F = Filenames::in(P, download_name);
    filename *TF = Patterns::find_file_in_subdirectory(wv->weave_web, wv->pattern, I"Embedding",
        I"Download.html");
    if (TF == NULL) {
        WebErrors::issue_at(I"Downloads are not supported", wv->current_weave_line);
    } else {
        Swarm::ensure_plugin(wv, I"Downloads");
        asset_rule *R = Assets::new_rule(NULL, I"", I"privately copy", NULL);
        pathname *TOP =
            Assets::include_asset(OUT, R, wv->weave_web, F, NULL,
                wv->pattern, wv->weave_to, wv->reportage, wv->weave_colony);
        if (TOP == NULL) TOP = Filenames::up(F);
        TEMPORARY_TEXT(url)
        TEMPORARY_TEXT(size)
        Pathnames::relative_URL(url, Filenames::up(wv->weave_to), TOP);
        WRITE_TO(url, "%S", Filenames::get_leafname(F));
        int N = Filenames::size(F);
        if (N > 0) Describe the file size13.1
        else WebErrors::issue_at(I"Download file missing or empty",
                wv->current_weave_line);
        filename *D = Filenames::from_text(download_name);
        Bibliographic::set_datum(wv->weave_web, I"File Name",
            Filenames::get_leafname(D));
        Bibliographic::set_datum(wv->weave_web, I"File URL", url);
        Bibliographic::set_datum(wv->weave_web, I"File Details", size);
        Collater::for_web_and_pattern(OUT, wv->weave_web, wv->pattern,
            TF, into_file, wv->weave_colony, wv->reportage);
        WRITE("\n");
        DISCARD_TEXT(url)
        DISCARD_TEXT(size)
    }
}

§13.1. Describe the file size13.1 =

    WRITE_TO(size, " (");
    if (Str::len(filetype) > 0) WRITE_TO(size, "%S, ", filetype);
    int x = 0, y = 0;
    text_stream *unit = I" byte"; x = N; y = 0;
    if (N > 1) { unit = I" bytes"; }
    if (N >= 1024) { unit = I"kB"; x = 10*N/1024; y = x%10; x = x/10; }
    if (N >= 1024*1024) { unit = I"MB"; x = 10*N/1024/1024; y = x%10; x = x/10; }
    if (N >= 1024*1024*1024) { unit = I"GB"; x = 10*N/1024/1024/1024; y = x%10; x = x/10; }
    WRITE_TO(size, "%d", x);
    if (y > 0) WRITE_TO(size, ".%d", y);
    WRITE_TO(size, "%S", unit);
    WRITE_TO(size, ")");

§14. 

void HTMLWeaving::render_HTML_extract(OUTPUT_STREAM, weave_order *wv, text_stream *leafname) {
    filename *F = Filenames::in(
        Pathnames::down(wv->weave_web->path_to_web, I"HTML"), leafname);
    HTML_OPEN_WITH("div", "class=\"inweb-extract\"");
    FILE *B = BinaryFiles::try_to_open_for_reading(F);
    if (B == NULL) {
        WebErrors::issue_at(I"Unable to find this HTML extract", wv->current_weave_line);
    } else {
        while (TRUE) {
            int c = getc(B);
            if (c == EOF) break;
            PUT((inchar32_t) c);
        }
        BinaryFiles::close(B);
    }
    HTML_CLOSE("div");
    WRITE("\n");
}

void HTMLWeaving::render_HTML_player(OUTPUT_STREAM, weave_order *wv, text_stream *name, int audio, int w, int h) {
    text_stream *subdir = (audio)?I"Audio":I"Video";
    filename *F = Filenames::in(Pathnames::down(wv->weave_web->path_to_web, subdir), name);
    asset_rule *R = Assets::new_rule(NULL, I"", I"privately copy", NULL);
    Assets::include_asset(OUT, R, wv->weave_web, F, NULL,
        wv->pattern, wv->weave_to, wv->reportage, wv->weave_colony);
    HTML_OPEN_WITH("p", "class=\"center-p\"");
    if (audio) {
        WRITE("<audio controls>\n");
        WRITE("<source src=\"%S\" type=\"audio/mpeg\">\n", name);
        WRITE("Your browser does not support the audio element.\n");
        WRITE("</audio>\n");
    } else {
        if ((w > 0) && (h > 0))
            WRITE("<video width=\"%d\" height=\"%d\" controls>", w, h);
        else if (w > 0)
            WRITE("<video width=\"%d\" controls>", w);
        else if (h > 0)
            WRITE("<video height=\"%d\" controls>", h);
        else
            WRITE("<video controls>");
        WRITE("<source src=\"%S\" type=\"video/mp4\">\n", name);
        WRITE("Your browser does not support the video tag.\n");
        WRITE("</video>\n");
    }
    HTML_CLOSE("p");
    WRITE("\n");
}

void HTMLWeaving::render_embedding(OUTPUT_STREAM, weave_order *wv, text_stream *ID,
    text_stream *service, int w, int h, filename *into_file) {
    if (w == 0) w = 720;
    if (h == 0) h = 405;
    TEMPORARY_TEXT(CW)
    TEMPORARY_TEXT(CH)
    WRITE_TO(CW, "%d", w); WRITE_TO(CH, "%d", h);
    TEMPORARY_TEXT(embed_leaf)
    WRITE_TO(embed_leaf, "%S.html", service);
    filename *F = Patterns::find_file_in_subdirectory(wv->weave_web, wv->pattern, I"Embedding", embed_leaf);
    DISCARD_TEXT(embed_leaf)
    if (F == NULL) {
        WebErrors::issue_at(I"This is not a supported service", wv->current_weave_line);
    } else {
        Bibliographic::set_datum(wv->weave_web, I"Content ID", ID);
        Bibliographic::set_datum(wv->weave_web, I"Content Width", CW);
        Bibliographic::set_datum(wv->weave_web, I"Content Height", CH);
        HTML_OPEN_WITH("p", "class=\"center-p\"");
        Collater::for_web_and_pattern(OUT, wv->weave_web, wv->pattern,
            F, into_file, wv->weave_colony, wv->reportage);
        HTML_CLOSE("p");
        WRITE("\n");
    }
    DISCARD_TEXT(CW)
    DISCARD_TEXT(CH)
}

int HTMLWeaving::caption(match_results *mr, markdown_item *item, int *pos) {
    if ((item->type == UNORDERED_LIST_ITEM_MIT) &&
        (item->down) &&
        (item->down->type == PARAGRAPH_MIT) &&
        (Regexp::match(mr, item->down->stashed, U"%(carousel%)"))) {
        if (pos) *pos = 0;
        return TRUE;
    }
    if ((item->type == UNORDERED_LIST_ITEM_MIT) &&
        (item->down) &&
        (item->down->type == PARAGRAPH_MIT) &&
        (Regexp::match(mr, item->down->stashed, U"%(carousel \"(%c+)\"%)"))) {
        if (pos) *pos = 0;
        return TRUE;
    }
    if ((item->type == UNORDERED_LIST_ITEM_MIT) &&
        (item->down) &&
        (item->down->type == PARAGRAPH_MIT) &&
        (Regexp::match(mr, item->down->stashed, U"%(carousel \"(%c+)\" captioned below%)"))) {
        if (pos) *pos = -1;
        return TRUE;
    }
    if ((item->type == UNORDERED_LIST_ITEM_MIT) &&
        (item->down) &&
        (item->down->type == PARAGRAPH_MIT) &&
        (Regexp::match(mr, item->down->stashed, U"%(carousel \"(%c+)\" captioned above%)"))) {
        if (pos) *pos = 1;
        return TRUE;
    }
    return FALSE;
}

int HTMLWeaving::render_ul_as_carousel(OUTPUT_STREAM, int mode, weave_order *wv,
    markdown_item *md, markdown_variation *variation) {
    match_results mr = Regexp::create_mr();
    int not = FALSE, of = 0;
    for (markdown_item *item = md->down; item; item = item->next) {
        if (HTMLWeaving::caption(&mr, item, NULL) == FALSE) {
            not = TRUE;
            break;
        }
        of++;
    }
    if (not) {
        Regexp::dispose_of(&mr);
        return FALSE;
    }

    int count = 1;
    for (markdown_item *item = md->down; item; item = item->next) {
        int positioning = 0;
        HTMLWeaving::caption(&mr, item, &positioning);
        TEMPORARY_TEXT(carousel_id)
        TEMPORARY_TEXT(carousel_dots_id)
        HTMLWeaving::render_carousel_top(OUT, 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) {
            MDRenderer::recurse(OUT, (void *) wv, c, m, variation);
            m = m & (~EXISTING_PAR_MDRMODE);
        }
        HTMLWeaving::render_carousel_bottom(OUT, wv, count, of, carousel_id, carousel_dots_id, mr.exp[0], positioning);
        DISCARD_TEXT(carousel_id)
        DISCARD_TEXT(carousel_dots_id)
        count++;
    }
    return TRUE;
}

void HTMLWeaving::render_carousel_top(OUTPUT_STREAM, weave_order *wv, int slide_number, int slide_of,
    text_stream *carousel_id, text_stream *carousel_dots_id, text_stream *caption, int positioning) {
    int N = wv->carousel_number;
    Swarm::ensure_plugin(wv, I"Carousel");
    text_stream *caption_class = NULL;
    if ((Str::len(caption) == 0) || (positioning == 0)) caption_class = I"carousel-caption";
    else if (positioning > 0) caption_class = I"carousel-caption-above";
    else if (positioning < 0) caption_class = I"carousel-caption-below";
    text_stream *slide_count_class = I"carousel-number";
    WRITE_TO(carousel_id, "carousel-no-%d", N);
    WRITE_TO(carousel_dots_id, "carousel-dots-no-%d", N);
    if (slide_number == 1) {
        WRITE("<div class=\"carousel-container\" id=\"%S\">\n", carousel_id);
    }
    WRITE("<div class=\"carousel-slide fading-slide\"");
    if (slide_number == 1) WRITE(" style=\"display: block;\"");
    else WRITE(" style=\"display: none;\"");
    WRITE(">\n");
    if (positioning > 0) Place caption here14.1;
    WRITE("<div class=\"%S\">%d / %d</div>\n",
        slide_count_class, slide_number, slide_of);
    WRITE("<div class=\"carousel-content\">");
}

void HTMLWeaving::render_carousel_bottom(OUTPUT_STREAM, weave_order *wv, int slide_number, int slide_of,
    text_stream *carousel_id, text_stream *carousel_dots_id, text_stream *caption, int positioning) {
    text_stream *caption_class = NULL;
    if ((Str::len(caption) == 0) || (positioning == 0)) caption_class = I"carousel-caption";
    else if (positioning > 0) caption_class = I"carousel-caption-above";
    else if (positioning < 0) caption_class = I"carousel-caption-below";
    WRITE("</div>\n");
    if (positioning <= 0) Place caption here14.1;
    WRITE("</div>\n");
    if (slide_number == slide_of) {
        WRITE("<a class=\"carousel-prev-button\" ");
        WRITE("onclick=\"carouselMoveSlide(&quot;%S&quot;, &quot;%S&quot;, -1)\"",
            carousel_id, carousel_dots_id);
        WRITE(">&#10094;</a>\n");
        WRITE("<a class=\"carousel-next-button\" ");
        WRITE("onclick=\"carouselMoveSlide(&quot;%S&quot;, &quot;%S&quot;, 1)\"",
            carousel_id, carousel_dots_id);
        WRITE(">&#10095;</a>\n");
        WRITE("</div>\n");
        WRITE("<div class=\"carousel-dots-container\" id=\"%S\">\n", carousel_dots_id);
        for (int i=1; i<=slide_of; i++) {
            if (i == 1)
                WRITE("<span class=\"carousel-dot carousel-dot-active\" ");
            else
                WRITE("<span class=\"carousel-dot\" ");
            WRITE("onclick=\"carouselSetSlide(&quot;%S&quot;, &quot;%S&quot;, %d)\"",
                carousel_id, carousel_dots_id, i-1);
            WRITE("></span>\n");
        }
        WRITE("</div>\n");
        wv->carousel_number++;
    }
}

§14.1. Place caption here14.1 =

    if (Str::len(caption) > 0)
        WRITE("<div class=\"%S\">%S</div>\n", caption_class, caption);

§15. EPUB-only methods. 

int HTMLWeaving::begin_weaving_EPUB(weave_format *wf, ls_web *W, ls_pattern *pattern) {
    TEMPORARY_TEXT(T)
    WRITE_TO(T, "%S", Bibliographic::get_datum(W, I"Title"));
    WeavingDetails::set_as_ebook(W, Epub::new(T, "P"));
    filename *CSS = Patterns::find_file_in_subdirectory(W, pattern, I"Base", I"Base.css");
    Epub::use_CSS_throughout(WeavingDetails::get_as_ebook(W), CSS);
    Epub::attach_metadata(WeavingDetails::get_as_ebook(W), U"identifier", T);
    DISCARD_TEXT(T)

    pathname *P = WebStructure::woven_folder(W, 2);
    WeavingDetails::set_redirect_weaves_to(W, Epub::begin_construction(WeavingDetails::get_as_ebook(W), P, NULL));
    Shell::copy(CSS, WeavingDetails::get_redirect_weaves_to(W), "");
    return SWARM_SECTIONS_SWM;
}

void HTMLWeaving::end_weaving_EPUB(weave_format *wf, ls_web *W, ls_pattern *pattern) {
    Epub::end_construction(WeavingDetails::get_as_ebook(W));
}