Markdown

label("Save it as **notes.md** before you *quit*.").markdown()
label(tr("release-note")).markdown()          // a translated string
label(move || draft.get()).markdown()         // live, as the user types

.markdown() reads a label’s text as inline markdown: the markers are stripped and what they marked becomes styled runs in the one label.

Why it parses at run time

The string a label shows is usually not a literal. It is a translation picked from the locale bundle at run time, a value off the network, or text a user is typing. A compile-time macro can only see literals, which is the one case that needs it least, so the parse happens on the string the label actually receives, every time it changes.

The cost is a parse per update of a label’s worth of text. The parser allocates only the output string and its runs, and it is about two hundred lines in day-pieces with no crate dependency.

The grammar

Styles nest: **bold with *italic* inside** gives three runs. A code span is literal inside, so `**not bold**` shows the asterisks.

Anything unrecognized is text. An unclosed **, a stray _ inside a word, or a [ with no ](…) after it stays exactly as typed. That is markdown’s own rule, and it keeps a half-typed string in a live editor from flickering between readings on every keystroke.

Block constructs are not parsed. Headings, lists, quotes, tables and paragraph breaks are layout, and layout in Day is column, form, list. A label is one paragraph; this is the markup that fits inside one.

Links

A [text](url) run draws as a link and reports its target when tapped:

label(tr("terms-blurb")).markdown()                          // opens the target
label(tr("terms-blurb")).markdown().on_link(|url| route(url)) // or handle it yourself
label("Open [**Navigate**](#navigate) or [Settings](#settings).").markdown()

Without .on_link(), a target beginning with # navigates to the route after the hash: #settings calls navigate("settings"). This uses the existing navigation rules, including paths and query parameters (#mail/inbox?filter=unread), percent escapes, and the empty route (#, which pops the innermost stack to its root). Unknown routes are ignored; they never open externally. Other targets open in the platform’s default handler, including URLs with a fragment such as https://daybrite.dev/#docs.

The link piece and TextBuilder::link use the same behavior. A custom .on_link() receives the original target and overrides both navigation and external opening. Call open_link(target) from the handler to use the default for targets you do not handle. The route must belong to a registered navigation surface; a separate Settings window, for example, needs an app handler that calls day::open_preferences().

Activation is Cap::TextLinks, which is narrower than run rendering. Where it is missing the link still draws; the tap does nothing. See text-runs.md for the per-toolkit table.

Escaping user text

.markdown() on a string a user supplied means their asterisks become emphasis. When the text is data rather than markup, leave the modifier off — a plain label never interprets anything.