386. A sheet of emoji is the font’s own contents

Date: 2026-09-17

Status

Accepted. Adds the showcase’s thirteenth screen, and the reader-facing half of ADR-0384.

Context

ADR-0384 moved the emoji face out of goldberry-core and into an artifact an application opts into, because CC BY-SA asks for attribution where the work is seen. That left two things unsaid. Nothing in the showcase drew an emoji, so the toolkit shipped a font nobody could look at; and nothing anywhere showed what taking the obligation on looks like, which is the part an application author actually has to copy.

The Icons screen is the shape of the answer — a searchable sheet of every bundled icon — and it is deliberately not the same screen. An icon is a path the application holds and hands to a box. An emoji is text: a code point drawn through whichever face the cascade picked, which is §6.1’s font chain and one font-family declaration.

Decision

A second sheet, beside the first, built from the face’s own cmap.

• FaceCoverage.codePoints(bytes) reads a TrueType cmap — formats 4 and 12 — and answers which characters a face has. Java rather than hb_face_collect_unicodes, for GifDecoder’s reason: the table is two arrays of ranges, and binding a set object and its iterator across FFM for a question asked once per face costs more than owning the format. Unreadable bytes are an empty answer, because the caller is asking what is in a face.
• The sheet is filtered to Character.isEmojiPresentation, and not to Character.isEmoji: the second is true of 0, # and ↔, so a sheet built on it opens on the ASCII digits. 1205 of OpenMoji’s 1845 characters are pictures on their own.
• The names are Character.getName — Unicode’s own, out of the JDK, so a search for “cat” works and no second asset is fetched. The hex matches too, because the other way somebody looks for an emoji is with a U+231B from a bug report.
• The screen carries the credit: OpenMoji, openmoji.org, CC BY-SA 4.0, in the note under the title. That is what an About box would do, and it is the demonstration ADR-0384 owed.
• Everything else is the Icons screen’s and is shared rather than copied: the reflow arithmetic (IconsScreen.columnsFor), the row pitch, the measured sheet (IconSheet) and the virtualized list of padded rows.
• The gallery golden for it uses a font book, alone among the gallery images: the others are taken with the one-font renderer, which ignores font-family — and a picture of an emoji sheet drawn in Inter is a picture of 1205 .notdef boxes.
• Fonts now falls back when the emoji face is absent rather than throwing: a stylesheet naming font-family: OpenMoji in an application without the artifact draws in the UI face and says so once in the log. The cascade runs inside a render pass, and a missing optional artifact must not be able to turn a window into no text at all.

Consequences

• Thirteen screens, and no digit moved: Ctrl+1…Ctrl+0 still name the first ten, and the two sheets are reached by the strip, the arrows and Edit ▸ Go to — which is exactly what ADR-0307 decided when the eleventh screen arrived.
• Every gallery golden is re-blessed for one more tab in the strip. The change is 547 pixels wide and is the tab.
• :example depends on :emoji, which is the first application in this repository to opt into an artifact with an obligation attached — and EmojiScreenTest asserts that the credit is on the screen, not merely that the face loaded.
• FaceCoverage is public and general: an emoji picker is the first caller, and “does this face cover this script” is the same question.