Add style to pandoc HTML render.

header.html

<script type="module">
  import mermaid from 'https://cdn.jsdelivr.net/npm/[email protected]/dist/mermaid.esm.min.mjs';
  mermaid.initialize({ startOnLoad: false });
  await mermaid.run({
    nodes: document.querySelectorAll('pre.mermaid > code:first-child'),
  });

  function findMermaidSvg(child) {
    if (child.tagName === "A" || child.tagName === "BUTTON") {
      return null;
    }
    while ((child = child.parentElement) !== null) {
      if (child.tagName === "PRE" && child.classList.contains("mermaid")) {
        return child.querySelector("svg");
      }
    }
    return null;
  }

  // Open the SVG Mermaid diagram to new window
  function mermaidHandler(ev) {
    const svgElement = findMermaidSvg(ev.target);
    if (svgElement === null) {
      return;
    }
    const text = new XMLSerializer().serializeToString(svgElement);
    const blob = new Blob([text], { type: "image/svg+xml" });
    const url = URL.createObjectURL(blob);
    const win = open(url);
    win.addEventListener("unload", () => {
      URL.revokeObjectURL(url);
    });
  }

  // Handle left click
  document.addEventListener("click", (ev) => mermaidHandler(ev));
  // Handle middle click
  document.addEventListener("auxclick", (ev) => mermaidHandler(ev));
</script>

meta.yml

title: Document title
subtitle: Document subtitle
author:
  - PENAUD Loïc <[email protected]>
lang: fr-FR

pandoc.css

/*
 * I add this to html files generated with pandoc.
 */

html {
  font-size: 100%;
  overflow-y: scroll;
  -webkit-text-size-adjust: 100%;
  -ms-text-size-adjust: 100%;
}

body {
  color: #444;
  font-family: Georgia, Palatino, 'Palatino Linotype', Times, 'Times New Roman', serif;
  font-size: 12px;
  line-height: 1.7;
  padding: 1em;
  margin: auto;
  max-width: 42em;
  background: #fefefe;
}

pre.mermaid {
  cursor: pointer;
}

a {
  color: #0645ad;
  text-decoration: none;
}

a:visited {
  color: #0b0080;
}

a:hover {
  color: #06e;
}

a:active {
  color: #faa700;
}

a:focus {
  outline: thin dotted;
}

*::-moz-selection {
  background: rgba(255, 255, 0, 0.3);
  color: #000;
}

*::selection {
  background: rgba(255, 255, 0, 0.3);
  color: #000;
}

a::-moz-selection {
  background: rgba(255, 255, 0, 0.3);
  color: #0645ad;
}

a::selection {
  background: rgba(255, 255, 0, 0.3);
  color: #0645ad;
}

p {
  margin: 1em 0;
}

img {
  max-width: 100%;
}

h1, h2, h3, h4, h5, h6 {
  color: #111;
  line-height: 125%;
  margin-top: 2em;
  font-weight: normal;
}

h4, h5, h6 {
  font-weight: bold;
}

h1 {
  font-size: 2.5em;
}

h2 {
  font-size: 2em;
}

h3 {
  font-size: 1.5em;
}

h4 {
  font-size: 1.2em;
}

h5 {
  font-size: 1em;
}

h6 {
  font-size: 0.9em;
}

blockquote {
  color: #666666;
  margin: 0;
  padding-left: 3em;
  border-left: 0.5em #EEE solid;
}

hr {
  display: block;
  height: 2px;
  border: 0;
  border-top: 1px solid #aaa;
  border-bottom: 1px solid #eee;
  margin: 1em 0;
  padding: 0;
}

pre, code, kbd, samp {
  color: #000;
  font-family: monospace, monospace;
  _font-family: 'courier new', monospace;
  font-size: 0.98em;
}

pre {
  white-space: pre;
  white-space: pre-wrap;
  word-wrap: break-word;
}

b, strong {
  font-weight: bold;
}

dfn {
  font-style: italic;
}

ins {
  background: #ff9;
  color: #000;
  text-decoration: none;
}

mark {
  background: #ff0;
  color: #000;
  font-style: italic;
  font-weight: bold;
}

sub, sup {
  font-size: 75%;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
}

sup {
  top: -0.5em;
}

sub {
  bottom: -0.25em;
}

ul, ol {
  margin: 1em 0;
  padding: 0 0 0 2em;
}

li p:last-child {
  margin-bottom: 0;
}

ul ul, ol ol {
  margin: .3em 0;
}

dl {
  margin-bottom: 1em;
}

dt {
  font-weight: bold;
  margin-bottom: .8em;
}

dd {
  margin: 0 0 .8em 2em;
}

dd:last-child {
  margin-bottom: 0;
}

img {
  border: 0;
  -ms-interpolation-mode: bicubic;
  vertical-align: middle;
}

figure {
  display: block;
  text-align: center;
  margin: 1em 0;
}

figure img {
  border: none;
  margin: 0 auto;
}

figcaption {
  font-size: 0.8em;
  font-style: italic;
  margin: 0 0 .8em;
}

table {
  margin-bottom: 2em;
  border-bottom: 1px solid #ddd;
  border-right: 1px solid #ddd;
  border-spacing: 0;
  border-collapse: collapse;
}

table th {
  padding: .2em 1em;
  background-color: #eee;
  border-top: 1px solid #ddd;
  border-left: 1px solid #ddd;
}

table td {
  padding: .2em 1em;
  border-top: 1px solid #ddd;
  border-left: 1px solid #ddd;
  vertical-align: top;
}

.author {
  font-size: 1.2em;
  text-align: center;
}

@media only screen and (min-width: 480px) {
  body {
    font-size: 14px;
  }
}
@media only screen and (min-width: 768px) {
  body {
    font-size: 16px;
  }
}
@media print {
  * {
    background: transparent !important;
    color: black !important;
    filter: none !important;
    -ms-filter: none !important;
  }

  body {
    font-size: 12pt;
    max-width: 100%;
  }

  a, a:visited {
    text-decoration: underline;
  }

  hr {
    height: 1px;
    border: 0;
    border-bottom: 1px solid black;
  }

  a[href]:after {
    content: " (" attr(href) ")";
  }

  abbr[title]:after {
    content: " (" attr(title) ")";
  }

  .ir a:after, a[href^="javascript:"]:after, a[href^="#"]:after {
    content: "";
  }

  pre, blockquote {
    border: 1px solid #999;
    padding-right: 1em;
    page-break-inside: avoid;
  }

  tr, img {
    page-break-inside: avoid;
  }

  img {
    max-width: 100% !important;
  }

  @page :left {
    margin: 15mm 20mm 15mm 10mm;
}

  @page :right {
    margin: 15mm 10mm 15mm 20mm;
}

  p, h2, h3 {
    orphans: 3;
    widows: 3;
  }

  h2, h3 {
    page-break-after: avoid;
  }
}

pandoc.md

Pandoc style

At first I would like to thank killercup for this cool CSS.

Add Mermaid to the page.

Command line

pandoc --from gfm \
  --to html5 \
  --standalone \
  --toc \
  --self-contained \
  --metadata date="$(date -I)" \
  --metadata-file meta.yml \
  --css ./pandoc.css \
  -H ./header.html \
  --output output.html \
  input.md

Bash function

Inject the bash file to your .bashrc or .bash_aliases.

Usage :

md2html input.md output.html meta.yml
# If the files have the same prefix
md2html prefix*

pandoc.sh

#!/bin/bash

declare PANDOC_DIR="$(dirname "$(realpath "${BASH_SOURCE}")")"

function md2html () {
  local md yaml html
  local -a args
  until [ $# -eq 0 ]; do
    [[ "${1}" =~ ya?ml$ ]] && yaml="${1}"
    [[ "${1}" =~ html$ ]] && html="${1}"
    [[ "${1}" =~ md$ ]] && md="${1}"
    shift
  done
  if [ -z "${md}" ]; then
    echo "Cannot find markdown file input" >&2
    return 1
  fi
  args+=(--from gfm)
  args+=(--to html5)
  args+=(--standalone)
  args+=(--toc)
  args+=(--self-contained)
  args+=(--metadata "date=$(date -I)")
  if [ -z "${yaml}" ]; then
    args+=(--metadata-file "${3}")
  fi
  args+=("${PANDOC_DIR}/pandoc.css")
  args+=("${PANDOC_DIR}/header.html")
  if [ -z "${html}" ]; then
    html="${md%*.md}.html"
  fi
  args+=(--output "${html}")
  args+=("${1}")
  pandoc "$@"
}