hotty hosts

Version:  0.6, with SPEC.md 0.6
Status:   Draft. Guidance for hosts, not part of the protocol.
Licence:  CC BY 4.0

Abstract

A host draws a program's surfaces (SPEC.md §1). SPEC.md says what a host must do on the wire. This document says what a host should provide beyond it, so that a document looks the same on every host that follows it: for now, the font a host ships.

Nothing here is on the wire. A host doesn't report it, and a program can't ask for it. A document may use what it describes, but it can't count on it (§2.5), and a host that doesn't follow this document is still a host.

Contents

1. Introduction
2. Fonts
3. Implementations

Appendix: A. Rationale

1. Introduction

SPEC.md defines the wire, and SDK.md how a library presents it to a program. This document is for whoever writes a host: a terminal, a browser addon, a renderer. Where it and SPEC.md disagree, SPEC.md is right and this document is wrong.

The key words MUST, MUST NOT, SHOULD, SHOULD NOT and MAY are to be interpreted as in SPEC.md §2. A MUST here binds a host that follows this document, not every host. Licence terms bind every host that ships the font.

2. Fonts

2.1 The font

A host SHOULD ship one font: AdwaitaMono Nerd Font Propo, from Nerd Fonts v3.5.1, in its Regular (400), Bold (700), Italic (400) and Bold Italic (700) faces.

• Adwaita Mono is GNOME's monospace typeface, built on Iosevka. It is licensed under the SIL Open Font License 1.1, with no reserved font names.
• Nerd Fonts adds the icon sets that terminal programs draw with:
  • Material Design Icons, Font Awesome, Devicons, Codicons and Octicons;
  • Powerline's symbols and the rest of its sets (§2.4).
• Propo is the variant whose icons keep their own width. A host lays out text as HTML, not on the terminal's grid, so an icon takes the room it needs. The plain variant gives an icon one cell's advance and draws it past it, over the next letter. The Mono variant shrinks it into one cell.

The family is named "AdwaitaMono Nerd Font Propo", as Nerd Fonts names it. A host MUST NOT rename it. A document that names the family gets it on every host that follows this document.

Italic is the font's own, not Regular slanted by the engine, so it matches a terminal that draws its cells in Adwaita Mono (§2.5). The other weights come from the engine, which takes the nearest of the two.

2.2 Its place in the font lists

The font goes where a document's text reaches it without asking for it:

• monospace and ui-monospace: first. A document in monospace looks the same on every system.

• Every other generic family (serif, sans-serif, system-ui, cursive, fantasy, ui-serif, ui-sans-serif, ui-rounded): second, right after the system's own choice and before the families the system lists after it. A document's sans-serif stays the system's. What that font lacks, a Nerd Font icon or a symbol such as ⌘, comes from this font, and not from whichever font the system lists next (§A.4).

• emoji, math and fangsong keep the system's lists.

• --hotty-font (SPEC.md §8) is the terminal's font family, then this font, then monospace:

  --hotty-font: "JetBrains Mono", "AdwaitaMono Nerd Font Propo", monospace;
  

  A host that already puts the font first in monospace MAY leave it out here, as the two lists then mean the same.

A browser can't change what a generic family means inside a page, so a browser host does only the last step. There a document that names monospace itself gets the browser's monospace font, and reaches this one only through --hotty-font or by name.

2.3 Loading it

The font is about 1.35 MB per face as WOFF2, and about 4 MB per face uncompressed.

• A native host SHOULD embed the WOFF2 faces and decode them once per process, off the thread that draws, before its first surface needs them. Decoding all four takes about 85 ms on four threads. Every surface then shares the decoded faces.
• A browser host SHOULD serve the faces as files, declare them with @font-face in the host stylesheet, and let the browser fetch each face the first time a surface draws text in it. The surface's CSP (SPEC.md §7.2) allows the font's URL in font-src; that is the host's own grant, not the document's. A document's network policy doesn't change it.

2.4 Licences

A host that ships the font MUST ship, beside it:

• OFL.txt: the font's licence, the SIL Open Font License 1.1, with its copyright lines.
• NOTICE.txt: the icon sets Nerd Fonts adds, each with its version, licence and source, followed by each licence's text. The sets carry MIT, Apache-2.0, CC BY 4.0, OFL-1.1 and the Unlicense. CC BY 4.0 (Codicons, Font Awesome's icons) requires the attribution this file gives.

A host that lists its third-party components MUST list the font there too, with both texts. The OFL allows bundling the font with software that is sold, but not selling the font on its own.

The icon sets include brand logos: Apple's, Microsoft Windows', and many others. Their licences cover the drawings, not the trademarks. A host's own interface, defaults, documentation and screenshots SHOULD NOT show a brand's logo. A user who puts one in their own configuration takes that on themselves.

2.5 What a program can count on

Nothing: a program can't tell from the capabilities (SPEC.md §4) whether a host ships the font.

• A document that draws Nerd Font icons gets them on a host that follows this document, and boxes or another font's glyphs elsewhere. A program that shows icons SHOULD let its user switch them to text.
• Cells are the terminal's. The font plays no part in cells: the terminal draws them with its own fonts. hottyterm's default font is Adwaita Mono, the letters of this font, so until its user picks another, cells and surfaces look alike. Whether an icon shows in cells depends on the terminal. Ghostty embeds Symbols Nerd Font, and hottyterm with it. Elsewhere the user's font decides.

3. Implementations

Both ship OFL.txt and NOTICE.txt beside the faces. hottyterm lists the font in its third-party notices.

Appendix A. Rationale

Informative.

A.1 Why ship a font

Users rarely install a Nerd Font for an app. A program that draws an icon, a key's symbol or a file type's logo then shows boxes, or a glyph from whatever font the system falls back to, at its size and weight. With one font shipped, a surface looks the same on every system: monospace text lines up as the author saw it, and icons draw without asking.

A.2 Why not in the spec

A font in SPEC.md would bind every host to ship it, and let a document rely on it. The font is new, and how documents use it is still unknown. It can move into SPEC.md later, as a guarantee or as a capability, once hosts and programs have used it.

A.3 Why this font

• Nerd Fonts, because terminal programs already draw with it: prompts, file trees, status lines. A surface draws the same icons the user's terminal does.

• Adwaita Mono, out of the families Nerd Fonts patches:

  • its licence: the OFL with no reserved font names, so the patched font may be shipped under Nerd Fonts' name;
  • its look: an even, readable monospace, on the GNOME desktop by default;
  • static faces of its own for Regular, Bold, Italic and Bold Italic, which is all a host needs, and the faces a terminal draws its cells with when it uses Adwaita Mono.

  Fonts whose licences limit where they may be used (Apple's SF fonts and SF Symbols, Microsoft's Segoe) were left out, and so was Meslo, which is made from Apple's Menlo.

• One font, not two. A proportional font for the rest (Inter, say) would double the size and add no icons: the system's sans-serif serves text.

A.4 Why second, and not last

Fontconfig lists many families for each generic one: on a typical Linux desktop, sans-serif names over a hundred, and the user's installed Nerd Fonts are often among the first. With this font last, an icon in sans-serif text came from the first of those that had it. A plain Nerd Font gives an icon one cell's advance and draws it wider, so it covered the next letter. Second, right after the system's choice, the icon comes from the Propo faces unless the system's own sans-serif has it.

A side effect: a symbol the system's sans-serif lacks, such as ⌘ ⌥ ⇧ in Noto Sans, draws from this font, as Adwaita Mono draws it.

A.5 Why WOFF2

WOFF2 is a third of the size uncompressed faces take in a binary, and it is what a browser fetches anyway. A native host pays for it with about 85 ms of decoding, once per process and off the drawing thread.