margin-mail/public/message.css

/* The stylesheet inside a message's iframe.
 *
 * It is served raw out of public/ rather than bundled, because the frame is a document of its own
 * and cannot see the app's stylesheets. Every value it uses is a custom property that
 * src/screens/MessageBody.tsx writes onto the frame's root from the app's own computed tokens, so
 * this file holds the shape of a message body and no colour, no face and no size of its own.
 *
 * The two faces are declared again for the same reason: a child document does not inherit the
 * parent's @font-face rules, and without these a message renders in Georgia. They are the two
 * default slots; a face chosen in settings needs its declaration here as well. */

@font-face {
  font-family: "Hanken Grotesk";
  src: url("/fonts/HankenGrotesk-VF.ttf") format("truetype-variations");
  font-weight: 100 900;
  font-style: normal;
  font-display: block;
}

@font-face {
  font-family: "Literata";
  src: url("/fonts/Literata-VF.ttf") format("truetype-variations");
  font-weight: 200 900;
  font-style: normal;
  font-display: block;
}

@font-face {
  font-family: "Literata";
  src: url("/fonts/Literata-Italic-VF.ttf") format("truetype-variations");
  font-weight: 200 900;
  font-style: italic;
  font-display: block;
}

html {
  /* The parent measures scrollHeight to size the frame, so nothing in here may scroll itself. */
  overflow: hidden;
  /* What this document is, in its own words: `only light` for a page the sender painted and ours
     for everything else. It decides the canvas the browser paints before the body does, the colours
     it gives anything it draws itself, and what a rule inside the message would be told about
     `prefers-color-scheme`. Written from MessageBody.tsx the way every other value here is.

     The `only light` half is the one no mail client ships. A body pinned to a white page in a dark
     window is still a document, and a document with nothing to say about its own scheme gets the
     machine's, which puts a dark canvas and dark user agent colours under a page we just painted
     white. */
  color-scheme: var(--m-color-scheme);
}

body {
  margin: 0;
  max-width: var(--m-measure);
  /* Painted rather than left transparent, because a message that painted its own page is pinned to
     the light surface in both palettes and has to bring that surface with it. On the theme the
     value is the app's own paper and this rule is invisible. */
  background: var(--m-paper);
  color: var(--m-ink);
  font-family: var(--m-font-text);
  font-size: var(--m-size);
  /* 1.5 rather than the 1.6 this was drawn at. At 15px that is 22.5px a line against 24px, which
     is worth more on a long message than every margin in the pane put together, and it is still
     prose rather than a spreadsheet. Anything tighter than 1.45 and the text face stops being
     worth having. */
  line-height: 1.5;
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
}

/* Transactional mail is data rather than prose, so it reads in the interface face. */
body[data-plain] {
  font-family: var(--m-font-ui);
  font-size: var(--m-size-plain);
  line-height: 1.55;
}

p {
  margin: 0 0 12px;
}

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

a {
  color: inherit;
  text-decoration: underline;
  text-underline-offset: 2px;
}

/* A sender's image is whatever size the sender made it, and the pane is not that wide. */
img {
  max-width: 100%;
  height: auto;
}

table {
  max-width: 100%;
  border-collapse: collapse;
}

blockquote {
  margin: 0 0 12px;
  padding-left: 14px;
  border-left: 2px solid var(--m-line);
  color: var(--m-faint);
}

pre,
code {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.92em;
}

pre {
  padding: 10px 12px;
  border-radius: 5px;
  background: var(--m-wash);
  overflow-x: auto;
}

hr {
  height: 1px;
  margin: 16px 0;
  border: 0;
  background: var(--m-line);
}