✅(frontend) cover present from block

Exercise block-to-slide mapping and the editor side-menu action.

Keep coverage scoped to starting the presenter from a block.

src/frontend/apps/e2e/__tests__/app-impress/presenter-mode.spec.ts

@@ -382,6 +382,27 @@ test.describe('Presenter Mode', () => {
     );
   });
 
+  test('opens the presenter at the targeted slide from a block side menu', async ({
+    page,
+    browserName,
+  }) => {
+    await createDoc(page, 'presenter-side-menu', browserName, 1);
+    await writeMultiSlideDoc(page);
+
+    await page
+      .locator('.bn-block-outer')
+      .filter({ hasText: 'Slide two' })
+      .first()
+      .hover();
+    await page.locator('.bn-side-menu > button').last().click();
+    await page.getByRole('menuitem', { name: 'Present from here' }).click();
+
+    const overlay = page.getByRole('dialog', { name: 'Presenter mode' });
+    await expect(overlay).toBeVisible();
+    await expect(overlay.getByText('3 / 4')).toBeVisible();
+    await expect(overlay.getByText('Slide two')).toBeVisible();
+  });
+
   test('opens presenter deep-links and normalizes slide params', async ({
     page,
     browserName,

src/frontend/apps/impress/src/features/docs/doc-presenter/__tests__/useSlides.spec.ts

@@ -1,6 +1,10 @@
 import { describe, expect, test } from 'vitest';
 
-import { getSlideTitle, splitBlocksIntoSlides } from '../hooks/useSlides';
+import {
+  getContentSlideIndexForBlock,
+  getSlideTitle,
+  splitBlocksIntoSlides,
+} from '../hooks/useSlides';
 import type { PresenterBlock } from '../types';
 
 type TestBlock = PresenterBlock;
@@ -23,13 +27,14 @@ const textContent = (text: string) => ({
   type: 'text' as const,
 });
 
-const para = (text = 'hello'): TestBlock =>
+const para = (text = 'hello', id?: string): TestBlock =>
   block('paragraph', {
     content: text === '' ? [] : [textContent(text)],
+    ...(id ? { id } : {}),
   });
 
-const divider = (children: TestBlock[] = []): TestBlock =>
-  block('divider', { children });
+const divider = (children: TestBlock[] = [], id?: string): TestBlock =>
+  block('divider', { children, ...(id ? { id } : {}) });
 
 const image = (): TestBlock => block('image', { props: { url: 'x' } });
 
@@ -201,6 +206,134 @@ describe('splitBlocksIntoSlides', () => {
   });
 });
 
+describe('getContentSlideIndexForBlock', () => {
+  test('returns the slide containing a regular block', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [para('a', 'a'), divider(), para('b', 'b'), para('c', 'c')],
+        'c',
+      ),
+    ).toBe(1);
+  });
+
+  test('returns the following slide for a divider', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [para('a', 'a'), divider(undefined, 'divider'), para('b', 'b')],
+        'divider',
+      ),
+    ).toBe(1);
+  });
+
+  test('returns the first non-empty following slide for consecutive dividers', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [
+          para('a', 'a'),
+          divider(undefined, 'first-divider'),
+          divider(undefined, 'second-divider'),
+          para('b', 'b'),
+        ],
+        'first-divider',
+      ),
+    ).toBe(1);
+  });
+
+  test('skips empty-only slides after dividers when mapping divider links', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [
+          para('a', 'a'),
+          divider(undefined, 'first-divider'),
+          para('', 'empty-after-divider'),
+          divider(undefined, 'second-divider'),
+          para('b', 'b'),
+        ],
+        'first-divider',
+      ),
+    ).toBe(1);
+  });
+
+  test('maps a stripped empty block after a divider to the following content slide', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [
+          para('a', 'a'),
+          divider(undefined, 'divider'),
+          para('', 'empty-after-divider'),
+          para('b', 'b'),
+        ],
+        'empty-after-divider',
+      ),
+    ).toBe(1);
+  });
+
+  test('maps a stripped empty block before a divider to the previous content slide', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [
+          para('a', 'a'),
+          para('', 'empty-before-divider'),
+          divider(undefined, 'divider'),
+          para('b', 'b'),
+        ],
+        'empty-before-divider',
+      ),
+    ).toBe(0);
+  });
+
+  test('maps a stripped empty-only slide to the next rendered content slide', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [
+          para('a', 'a'),
+          divider(undefined, 'first-divider'),
+          para('', 'empty-between-dividers'),
+          divider(undefined, 'second-divider'),
+          para('b', 'b'),
+        ],
+        'empty-between-dividers',
+      ),
+    ).toBe(1);
+  });
+
+  test('maps a leading divider to the first content slide', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [divider(undefined, 'divider'), para('a', 'a')],
+        'divider',
+      ),
+    ).toBe(0);
+  });
+
+  test('maps a trailing divider to the last rendered content slide', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [para('a', 'a'), divider(undefined, 'divider')],
+        'divider',
+      ),
+    ).toBe(0);
+  });
+
+  test('finds blocks nested under a structural divider', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [para('a', 'a'), divider([para('nested', 'nested')], 'divider')],
+        'nested',
+      ),
+    ).toBe(1);
+  });
+
+  test('returns the first content slide when the block is missing', () => {
+    expect(
+      getContentSlideIndexForBlock(
+        [para('a', 'a'), divider(), para('b', 'b')],
+        'x',
+      ),
+    ).toBe(0);
+  });
+});
+
 const heading = (text: string): TestBlock =>
   block('heading', { content: [textContent(text)] });