Fonts: a new asset type, picked from the server or dropped in, worn by text objects (#74)

A font asset holds a file and nothing else, the twin of a texture: the server keeps it
content-addressed under data/fonts/{sha256}.{ext}, with the format read from the file's own
four-byte signature (finfo reports fonts inconsistently across libmagic versions). A text
wears one through its ordinary Font property, so overrides, reset, undo and the Properties
node come for free; no font means the editor's own typeface.

The picker lists everything the server holds and renders each row in the face it offers.
The family name is gm-font-<hash16>, never the name inside the file, so two "Regular" cannot
collide. WorldViewport.syncText is the single place that draws it, which covers scene, game
preview and play at once.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/model/Asset.ts

@@ -100,6 +100,16 @@ export interface ShaderAsset extends AssetBase {
   graph: Graph;
 }
 
+/**
+ * `file` names the typeface in `data/fonts/` the way a texture names its image: content-addressed
+ * `{sha256}.{ext}`, empty when the upload failed. A text object wears it through its `font`
+ * property; the family the browser knows it under is derived from the file name, see `model/font`.
+ */
+export interface FontAsset extends AssetBase {
+  type: 'font';
+  file: string;
+}
+
 export type Asset =
   | SpriteAsset
   | CameraAsset
@@ -111,7 +121,8 @@ export type Asset =
   | TextureAsset
   | AnimationAsset
   | StateMachineAsset
-  | ShaderAsset;
+  | ShaderAsset
+  | FontAsset;
 
 /** The assets edited as a node graph – what the graph canvas and the graph commands work on. */
 export type GraphAsset = BehaviorAsset | StateMachineAsset | ShaderAsset;

src/core/model/AssetTypes.ts

@@ -10,6 +10,7 @@ export const ASSET_TYPES = [
   'animation',
   'statemachine',
   'shader',
+  'font',
 ] as const;
 
 export type AssetType = (typeof ASSET_TYPES)[number];
@@ -26,15 +27,17 @@ export const ASSET_TYPE_LABELS: Record<AssetType, string> = {
   animation: 'Animation',
   statemachine: 'State machine',
   shader: 'Shader',
+  font: 'Font',
 };
 
 /**
  * Textures and animations are not placeable: they are pictures a sprite wears through `texture`,
- * as a shader is worn through `shader`. A state machine is not either: a behavior refers to it by id.
+ * as a shader is worn through `shader` and a font through `font`. A state machine is not either:
+ * a behavior refers to it by id.
  */
 export type PlaceableAssetType = Exclude<
   AssetType,
-  'scene' | 'texture' | 'animation' | 'statemachine' | 'shader'
+  'scene' | 'texture' | 'animation' | 'statemachine' | 'shader' | 'font'
 >;
 
 const NOT_PLACEABLE: ReadonlySet<AssetType> = new Set([
@@ -43,6 +46,7 @@ const NOT_PLACEABLE: ReadonlySet<AssetType> = new Set([
   'animation',
   'statemachine',
   'shader',
+  'font',
 ]);
 
 export function isPlaceableType(type: AssetType): type is PlaceableAssetType {

src/core/model/font.ts

@@ -0,0 +1,29 @@
+import type { FontAsset } from './Asset';
+import { findAsset, type Project } from './Project';
+
+/** Mirrors `FontStore::isValidName` on the server, where the name is derived from the bytes. */
+const FILE_PATTERN = /^[a-f0-9]{64}\.(ttf|otf|woff|woff2)$/;
+
+export function isFontFile(name: string): boolean {
+  return FILE_PATTERN.test(name);
+}
+
+/**
+ * The CSS family a file is registered under. Derived from the content-addressed name, so the same
+ * bytes are always one family and two uploads of one typeface cannot fight over a name – the name
+ * inside the font is never used for this, only for the asset's label.
+ */
+export function fontFamilyOf(file: string): string {
+  return `gm-font-${file.slice(0, 16)}`;
+}
+
+/** The file a `font` property points at, empty when the id is unset or no longer resolves. */
+export function fontFileOf(project: Project, id: string): string {
+  if (id === '') return '';
+  const asset = findAsset(project, id);
+  return asset?.type === 'font' ? asset.file : '';
+}
+
+export function isFontAsset(asset: { type: string }): asset is FontAsset {
+  return asset.type === 'font';
+}