feat(CompareBoard): orchestrate font preloading, pinning, and default seeding

src/features/CompareBoard/model/store/boardStore/boardStore.svelte.test.ts

@@ -4,7 +4,56 @@ import {
     describe,
     expect,
     it,
+    vi,
 } from 'vitest';
+
+/**
+ * Font orchestration is exercised in e2e (needs a real browser/queryClient).
+ * Here we stub the entity's font stores so the board's pure logic stays testable
+ * off the network — only `candidateFontIds` derivation is asserted at this level.
+ */
+const mockLifecycle = vi.hoisted(() => ({
+    touch: vi.fn(),
+    pin: vi.fn(),
+    unpin: vi.fn(),
+}));
+
+/**
+ * Catalog stub with four fonts so the seeding effect has material to pair.
+ * Seeding only fires when storage is empty AND nothing has been added yet, so
+ * the empty/add tests (which never flush before asserting) are unaffected.
+ */
+const mockCatalog = vi.hoisted(() => ({
+    fonts: [
+        { id: 'c0', name: 'C0' },
+        { id: 'c1', name: 'C1' },
+        { id: 'c2', name: 'C2' },
+        { id: 'c3', name: 'C3' },
+    ],
+}));
+
+vi.mock('$entities/Font', async importOriginal => {
+    const actual = await importOriginal<typeof import('$entities/Font')>();
+    class MockFontsByIdsStore {
+        setIds() {}
+        get fonts() {
+            return [];
+        }
+        get isLoading() {
+            return false;
+        }
+        destroy() {}
+    }
+    return {
+        ...actual,
+        FontsByIdsStore: MockFontsByIdsStore,
+        getFontLifecycleManager: () => mockLifecycle,
+        getFontCatalog: () => mockCatalog,
+        getFontUrl: () => 'https://example.com/font.woff2',
+    };
+});
+
+import { flushSync } from 'svelte';
 import {
     __resetBoard,
     getBoard,
@@ -92,6 +141,31 @@ describe('boardStore', () => {
         expect(board.focalId).toBe(b.id);
     });
 
+    it('seeds curated pairings from the catalog when storage is empty', () => {
+        const board = getBoard();
+        flushSync(); // let the seed effect run
+        expect(board.pairings.length).toBeGreaterThan(0);
+        expect(board.focalId).not.toBeNull();
+    });
+
+    it('does not seed when storage already has pairings', () => {
+        // pre-seed storage so a fresh board rehydrates instead of seeding
+        const first = getBoard();
+        const p = first.addPairing('Inter', 'Lora');
+        __resetBoard();
+        const restored = getBoard();
+        flushSync();
+        expect(restored.pairings).toHaveLength(1);
+        expect(restored.pairings[0].id).toBe(p.id);
+    });
+
+    it('collects every distinct candidate font id for preloading', () => {
+        const board = getBoard();
+        board.addPairing('Inter', 'Lora');
+        board.addPairing('Inter', 'Merriweather'); // Inter deduped
+        expect(new Set(board.candidateFontIds)).toEqual(new Set(['Inter', 'Lora', 'Merriweather']));
+    });
+
     it('exposes default per-role typography', () => {
         const board = getBoard();
         expect(board.typo.header.size).toBeGreaterThan(0);

src/features/CompareBoard/model/store/boardStore/boardStore.svelte.ts

@@ -7,8 +7,10 @@
  *
  * Typography is NOT owned here as an AdjustTypography store (features can't
  * import sibling features). Instead the board holds plain per-role typography
- * values, fed in via `setTypo` by `widgets/Board` (dependency inversion). Font
- * resolution/loading (Task 14) and frame measurement (Task 16) layer on later.
+ * values, fed in via `setTypo` by `widgets/Board` (dependency inversion).
+ *
+ * Font metadata is resolved + preloaded via the Font entity (candidate
+ * preloading, focal pinning). Frame measurement (Task 16) layers on later.
  */
 
 import {
@@ -16,6 +18,14 @@ import {
     DEFAULT_FONT_WEIGHT,
     DEFAULT_LETTER_SPACING,
     DEFAULT_LINE_HEIGHT,
+    type FontCatalogStore,
+    type FontLifecycleManager,
+    type FontLoadRequestConfig,
+    FontsByIdsStore,
+    type UnifiedFont,
+    getFontCatalog,
+    getFontLifecycleManager,
+    getFontUrl,
 } from '$entities/Font';
 import {
     type Pairing,
@@ -32,7 +42,10 @@ import {
     createPersistentStore,
     createSingleton,
 } from '$shared/lib';
-import { flushSync } from 'svelte';
+import {
+    flushSync,
+    untrack,
+} from 'svelte';
 
 /**
  * Compact persisted board shape. Font ids are abbreviated (`h`/`b`) to keep the
@@ -128,12 +141,126 @@ export class BoardStore {
      * localStorage-backed mirror of the board blob.
      */
     #storage = createPersistentStore<PersistedBoard>(BOARD_STORAGE_KEY, emptyBoard());
+    /**
+     * Batch font-metadata resolver, kept in sync with `candidateFontIds`.
+     */
+    #fontsByIds: FontsByIdsStore;
+    /**
+     * Font load/cache/eviction manager; pinned to keep on-screen fonts resident.
+     */
+    #lifecycle: FontLifecycleManager;
+    /**
+     * Paginated font catalog — source of fonts for default seeding.
+     */
+    #fontCatalog: FontCatalogStore;
+    /**
+     * One-shot guard: only seed a default board when storage was empty at
+     * construction (never re-seed after the user empties the board).
+     */
+    #shouldSeed: boolean;
+    /**
+     * Disposes the constructor's $effect.root. Must run on teardown.
+     */
+    #disposeEffects: () => void;
 
     constructor() {
         const stored = this.#storage.value;
         this.#pairings = stored.pairings.map(p => createPairing(p.h, p.b, p.id));
         this.#focalId = stored.focalId;
         this.#specimen = { ...stored.specimen };
+        this.#shouldSeed = stored.pairings.length === 0;
+
+        this.#lifecycle = getFontLifecycleManager();
+        this.#fontCatalog = getFontCatalog();
+        this.#fontsByIds = new FontsByIdsStore(this.candidateFontIds);
+
+        this.#disposeEffects = $effect.root(() => {
+            // Seed a curated default board the first time the catalog is ready and
+            // storage was empty — so the screen is never blank on first visit.
+            $effect(() => {
+                if (!this.#shouldSeed || this.#pairings.length > 0) {
+                    return;
+                }
+                const fonts = this.#fontCatalog.fonts;
+                if (fonts.length < 2) {
+                    return;
+                }
+                untrack(() => {
+                    this.#shouldSeed = false;
+                    const count = Math.min(4, Math.floor(fonts.length / 2));
+                    for (let i = 0; i < count; i++) {
+                        this.addPairing(fonts[i * 2].id, fonts[i * 2 + 1].id);
+                    }
+                });
+            });
+
+            // Keep the batch query's id set in sync with the board's candidates.
+            $effect(() => {
+                this.#fontsByIds.setIds(this.candidateFontIds);
+            });
+
+            // Preload every candidate font at its role weight (brief §Performance).
+            $effect(() => {
+                const configs = this.#candidateConfigs();
+                if (configs.length > 0) {
+                    this.#lifecycle.touch(configs);
+                }
+            });
+
+            // Pin the focal pairing's fonts so eviction never drops on-screen
+            // glyphs; unpin on focal/weight change via the cleanup return.
+            $effect(() => {
+                const focal = this.focal;
+                if (!focal) {
+                    return;
+                }
+                const headerWeight = this.#typo.header.weight;
+                const bodyWeight = this.#typo.body.weight;
+                const header = this.fontById(focal.headerFontId);
+                const body = this.fontById(focal.bodyFontId);
+                if (header) {
+                    this.#lifecycle.pin(header.id, headerWeight, header.features?.isVariable);
+                }
+                if (body) {
+                    this.#lifecycle.pin(body.id, bodyWeight, body.features?.isVariable);
+                }
+                return () => {
+                    if (header) {
+                        this.#lifecycle.unpin(header.id, headerWeight, header.features?.isVariable);
+                    }
+                    if (body) {
+                        this.#lifecycle.unpin(body.id, bodyWeight, body.features?.isVariable);
+                    }
+                };
+            });
+        });
+    }
+
+    /**
+     * Builds dedup'd font-load configs for every resolvable candidate font at its
+     * role weight (header fonts at header weight, body fonts at body weight).
+     * Unresolved fonts (metadata not yet fetched) are skipped.
+     */
+    #candidateConfigs(): FontLoadRequestConfig[] {
+        const configs: FontLoadRequestConfig[] = [];
+        const seen = new Set<string>();
+        const add = (fontId: string, weight: number) => {
+            const font = this.fontById(fontId);
+            if (!font) {
+                return;
+            }
+            const url = getFontUrl(font, weight);
+            if (!url || seen.has(url)) {
+                return;
+            }
+            seen.add(url);
+            configs.push({ id: font.id, name: font.name, weight, url, isVariable: font.features?.isVariable });
+        };
+        for (const pairing of this.#pairings) {
+            add(pairing.headerFontId, this.#typo.header.weight);
+            add(pairing.bodyFontId, this.#typo.body.weight);
+        }
+        return configs;
     }
 
     /**
@@ -196,6 +323,42 @@ export class BoardStore {
         this.#typo = { ...this.#typo, [role]: { ...values } };
     }
 
+    /**
+     * Every distinct font id referenced by any pairing (header or body). The
+     * preload set — kept in sync with the batch font resolver.
+     */
+    get candidateFontIds(): string[] {
+        const ids = new Set<string>();
+        for (const pairing of this.#pairings) {
+            ids.add(pairing.headerFontId);
+            ids.add(pairing.bodyFontId);
+        }
+        return [...ids];
+    }
+
+    /**
+     * Resolves a font id to its loaded metadata, or undefined if not yet fetched.
+     *
+     * @param id - Font entity id.
+     * @returns The font metadata, or undefined while loading.
+     */
+    fontById(id: string): UnifiedFont | undefined {
+        return this.#fontsByIds.fonts.find(f => f.id === id);
+    }
+
+    /**
+     * Resolves both fonts of a pairing for the UI.
+     *
+     * @param pairing - The pairing to resolve.
+     * @returns Header and body font metadata (each undefined while loading).
+     */
+    resolvePairingFonts(pairing: Pairing): { header?: UnifiedFont; body?: UnifiedFont } {
+        return {
+            header: this.fontById(pairing.headerFontId),
+            body: this.fontById(pairing.bodyFontId),
+        };
+    }
+
     /**
      * Adds a pairing to the end of the board. The first pairing added becomes
      * focal.
@@ -314,6 +477,8 @@ export class BoardStore {
      */
     destroy() {
         flushSync();
+        this.#disposeEffects();
+        this.#fontsByIds.destroy();
         this.#storage.destroy();
     }
 }