src/entities/Font/lib/sizeResolver/createFontRowSizeResolver.test.ts

@@ -1,7 +1,19 @@
 // @vitest-environment jsdom
-import { TextLayoutEngine } from '$shared/lib';
 import { installCanvasMock } from '$shared/lib/helpers/__mocks__/canvas';
-import { clearCache } from '@chenglou/pretext';
+import {
+    clearCache,
+    layout,
+} from '@chenglou/pretext';
+
+// Wrap pretext's `layout` in a spy-able mock so tests can assert call counts.
+// `vi.mock` is hoisted, so the import above receives the mocked module.
+vi.mock('@chenglou/pretext', async () => {
+    const actual = await vi.importActual<typeof import('@chenglou/pretext')>('@chenglou/pretext');
+    return {
+        ...actual,
+        layout: vi.fn(actual.layout),
+    };
+});
 import {
     beforeEach,
     describe,
@@ -112,13 +124,13 @@ describe('createFontRowSizeResolver', () => {
         const { resolver } = makeResolver();
         statusMap.set('inter@400', 'loaded');
 
-        const layoutSpy = vi.spyOn(TextLayoutEngine.prototype, 'layout');
+        const layoutSpy = vi.mocked(layout);
+        layoutSpy.mockClear();
 
         resolver(0);
         resolver(0);
 
         expect(layoutSpy).toHaveBeenCalledTimes(1);
-        layoutSpy.mockRestore();
     });
 
     it('calls layout() again when containerWidth changes (cache miss)', () => {
@@ -126,14 +138,14 @@ describe('createFontRowSizeResolver', () => {
         const { resolver } = makeResolver({ getContainerWidth: () => width });
         statusMap.set('inter@400', 'loaded');
 
-        const layoutSpy = vi.spyOn(TextLayoutEngine.prototype, 'layout');
+        const layoutSpy = vi.mocked(layout);
+        layoutSpy.mockClear();
 
         resolver(0);
         width = 100;
         resolver(0);
 
         expect(layoutSpy).toHaveBeenCalledTimes(2);
-        layoutSpy.mockRestore();
     });
 
     it('returns greater height when container narrows (more wrapping)', () => {

src/entities/Font/lib/sizeResolver/createFontRowSizeResolver.ts

@@ -1,4 +1,7 @@
-import { TextLayoutEngine } from '$shared/lib';
+import {
+    layout,
+    prepare,
+} from '@chenglou/pretext';
 import { generateFontKey } from '../../model/store/fontLifecycleManager/utils/generateFontKey/generateFontKey';
 import type {
     FontLoadStatus,
@@ -79,14 +82,13 @@ export interface FontRowSizeResolverOptions {
  * no DOM snap occurs.
  *
  * **Caching:** A `Map` keyed by `fontCssString|text|contentWidth|lineHeightPx`
- * prevents redundant `TextLayoutEngine.layout()` calls. The cache is invalidated
+ * prevents redundant `pretext.layout()` calls. The cache is invalidated
  * naturally because a change in any input produces a different cache key.
  *
  * @param options - Configuration and getter functions (all injected for testability).
  * @returns A function `(rowIndex: number) => number` for use as `VirtualList.itemHeight`.
  */
 export function createFontRowSizeResolver(options: FontRowSizeResolverOptions): (rowIndex: number) => number {
-    const engine = new TextLayoutEngine();
     // Key: `${fontCssString}|${text}|${contentWidth}|${lineHeightPx}`
     const cache = new Map<string, number>();
 
@@ -126,7 +128,11 @@ export function createFontRowSizeResolver(options: FontRowSizeResolverOptions):
             return cached;
         }
 
-        const { totalHeight } = engine.layout(previewText, fontCssString, contentWidth, lineHeightPx);
+        // Pretext docs recommend `layout()` (not `layoutWithLines`) for the
+        // resize hot path — pure arithmetic on cached segment widths, no canvas
+        // calls, no string allocations.
+        const prepared = prepare(previewText, fontCssString);
+        const { height: totalHeight } = layout(prepared, contentWidth, lineHeightPx);
         const result = totalHeight + options.chromeHeight;
         cache.set(cacheKey, result);
         return result;

src/shared/lib/helpers/TextLayoutEngine/TextLayoutEngine.svelte.ts

@@ -70,6 +70,14 @@ export interface LayoutResult {
  * **Canvas requirement:** pretext calls `document.createElement('canvas').getContext('2d')` on
  * first use and caches the context for the process lifetime. Tests must install a canvas mock
  * (see `__mocks__/canvas.ts`) before the first `layout()` call.
+ *
+ * @deprecated No live consumers remain — the only previous caller
+ * (`createFontRowSizeResolver`) now invokes pretext's `prepare` + `layout`
+ * directly (per pretext's "hot-path resize function" guidance). If you need
+ * single-font height-only measurement, use `prepare` + `layout` from
+ * `@chenglou/pretext` directly. If you need per-grapheme x/width data, see
+ * `CharacterComparisonEngine` (dual-font) or revive a slimmer wrapper.
+ * Slated for removal once it has been absent from `main` for a release cycle.
  */
 export class TextLayoutEngine {
     /**