feat(editor): add stress-accent (U+0301) toggle button to the bubble menu (closes #270)

Select a vowel and one click places a combining acute accent over it; clicking
again removes it (toggle). Inserts the literal Unicode char U+0301 right after
the letter — plain text, not a custom TipTap mark — so it survives HTML/Markdown
export, full-text search and public share with zero server/converter changes.
Insert/remove is a single transaction (one Ctrl+Z), inherits the letter's marks
(bold/italic/color), and restores the original selection so the active state
toggles correctly. Editable bubble menu only. New pure helper stress-accent.ts
(+ 5 unit tests). i18n: en 'Stress' / ru 'Ударение'.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/public/locales/en-US/translation.json

@@ -356,6 +356,7 @@
   "Strike": "Strike",
   "Code": "Code",
   "Spoiler": "Spoiler",
+  "Stress": "Stress",
   "Comment": "Comment",
   "Text": "Text",
   "Heading 1": "Heading 1",

apps/client/public/locales/ru-RU/translation.json

@@ -352,6 +352,7 @@
   "Strike": "Перечёркнутый",
   "Code": "Код",
   "Spoiler": "Спойлер",
+  "Stress": "Ударение",
   "Comment": "Комментарий",
   "Text": "Текст",
   "Heading 1": "Заголовок 1",

apps/client/src/features/editor/components/bubble-menu/bubble-menu.tsx

@@ -29,6 +29,37 @@ import { LinkSelector } from "@/features/editor/components/bubble-menu/link-sele
 import { useTranslation } from "react-i18next";
 import { showLinkMenuAtom } from "@/features/editor/atoms/editor-atoms";
 import { userAtom } from "@/features/user/atoms/current-user-atom";
+import {
+  hasStressAfterSelection,
+  toggleStressAccent,
+} from "./stress-accent";
+
+// Tabler has no acute-accent glyph (IconGrave is a tombstone), so we ship a
+// tiny local icon that mirrors the Tabler icon API ({ style, stroke }).
+function IconStress({
+  style,
+  stroke = 2,
+}: {
+  style?: React.CSSProperties;
+  stroke?: number;
+}) {
+  return (
+    <svg
+      xmlns="http://www.w3.org/2000/svg"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      strokeWidth={stroke}
+      strokeLinecap="round"
+      strokeLinejoin="round"
+      style={style}
+    >
+      <path d="M5 19l5 -12l5 12" />
+      <path d="M7.5 14h5" />
+      <path d="M13 5l4 -3" />
+    </svg>
+  );
+}
 
 export interface BubbleMenuItem {
   name: string;
@@ -77,6 +108,8 @@ export const EditorBubbleMenu: FC<EditorBubbleMenuProps> = (props) => {
         isCode: ctx.editor.isActive("code"),
         isComment: ctx.editor.isActive("comment"),
         isSpoiler: ctx.editor.isActive("spoiler"),
+        // A stress accent already sits right after the selection end.
+        isStress: hasStressAfterSelection(ctx.editor.state),
       };
     },
   });
@@ -118,6 +151,20 @@ export const EditorBubbleMenu: FC<EditorBubbleMenuProps> = (props) => {
       command: () => props.editor.chain().focus().toggleSpoiler().run(),
       icon: IconEyeOff,
     },
+    {
+      name: "Stress",
+      isActive: () => editorState?.isStress,
+      // Toggle the U+0301 combining accent right after the selected letter.
+      // The whole toggle is a single transaction, so one Ctrl+Z reverts it.
+      command: () => {
+        const editor = props.editor;
+        editor.view.dispatch(toggleStressAccent(editor.state));
+        editor.view.focus();
+      },
+      // Local SVG icon; cast to the Tabler icon type used by the other items.
+      // It renders with the same { style, stroke } props they are given.
+      icon: IconStress as unknown as typeof IconBold,
+    },
     {
       name: "Clear formatting",
       // Action, not a toggle — never show an active/highlighted state.

apps/client/src/features/editor/components/bubble-menu/stress-accent.test.ts

@@ -0,0 +1,94 @@
+import { describe, expect, it } from "vitest";
+import { Schema } from "@tiptap/pm/model";
+import { EditorState, TextSelection } from "@tiptap/pm/state";
+import {
+  STRESS_ACCENT,
+  hasStressAfterSelection,
+  toggleStressAccent,
+} from "./stress-accent";
+
+// Minimal ProseMirror schema: paragraph of text with a single `bold` mark.
+const schema = new Schema({
+  nodes: {
+    doc: { content: "block+" },
+    paragraph: {
+      group: "block",
+      content: "text*",
+      toDOM: () => ["p", 0],
+    },
+    text: { group: "inline" },
+  },
+  marks: {
+    bold: { toDOM: () => ["strong", 0] },
+  },
+});
+
+function makeState(
+  text: string,
+  from: number,
+  to: number,
+  marked = false,
+): EditorState {
+  const marks = marked ? [schema.marks.bold.create()] : [];
+  const textNode = schema.text(text, marks);
+  const doc = schema.node("doc", null, [
+    schema.node("paragraph", null, [textNode]),
+  ]);
+  const state = EditorState.create({ schema, doc });
+  return state.apply(
+    state.tr.setSelection(TextSelection.create(state.doc, from, to)),
+  );
+}
+
+describe("stress-accent", () => {
+  it("uses U+0301 as the combining accent", () => {
+    expect(STRESS_ACCENT).toHaveLength(1);
+    expect(STRESS_ACCENT.codePointAt(0)).toBe(0x0301);
+  });
+
+  it("inserts the accent right after the selected vowel", () => {
+    // "кот", select "о" (positions 2..3).
+    const state = makeState("кот", 2, 3);
+    expect(hasStressAfterSelection(state)).toBe(false);
+
+    const next = state.apply(toggleStressAccent(state));
+    expect(next.doc.textContent).toBe(`ко${STRESS_ACCENT}т`);
+    // Selection is preserved on the letter, so the button reads active.
+    expect(next.selection.from).toBe(2);
+    expect(next.selection.to).toBe(3);
+    expect(hasStressAfterSelection(next)).toBe(true);
+  });
+
+  it("removes the accent on a second toggle (round-trips to original)", () => {
+    const state = makeState("кот", 2, 3);
+    const inserted = state.apply(toggleStressAccent(state));
+    const removed = inserted.apply(toggleStressAccent(inserted));
+
+    expect(removed.doc.textContent).toBe("кот");
+    expect(hasStressAfterSelection(removed)).toBe(false);
+    expect(removed.selection.from).toBe(2);
+    expect(removed.selection.to).toBe(3);
+  });
+
+  it("inherits the letter's marks so the accent stays bold", () => {
+    // Whole word is bold; select "о".
+    const state = makeState("кот", 2, 3, true);
+    const next = state.apply(toggleStressAccent(state));
+
+    // The accent lands at positions 3..4 (right after "о")...
+    expect(next.doc.textBetween(3, 4)).toBe(STRESS_ACCENT);
+    // ...inside a bold text node, so it inherits the letter's bold mark.
+    const accentNode = next.doc.nodeAt(3);
+    expect(accentNode?.marks.some((m) => m.type.name === "bold")).toBe(true);
+  });
+
+  it("handles a selection at the end of the doc without throwing", () => {
+    // "а" is the whole paragraph; select it (1..2), end of content.
+    const state = makeState("а", 1, 2);
+    expect(hasStressAfterSelection(state)).toBe(false);
+
+    const next = state.apply(toggleStressAccent(state));
+    expect(next.doc.textContent).toBe(`а${STRESS_ACCENT}`);
+    expect(hasStressAfterSelection(next)).toBe(true);
+  });
+});

apps/client/src/features/editor/components/bubble-menu/stress-accent.ts

@@ -0,0 +1,41 @@
+import { EditorState, TextSelection, Transaction } from "@tiptap/pm/state";
+
+// U+0301 COMBINING ACUTE ACCENT — a plain Unicode combining char inserted
+// right after a vowel to render a Russian-style stress accent over it.
+// It is stored as literal text (not a TipTap mark), so it survives HTML/
+// Markdown export, full-text search and public share with zero server or
+// converter changes.
+export const STRESS_ACCENT = "́";
+
+// True when a stress accent already sits immediately after the selection end
+// (the single char following the selection). Used both for the toolbar
+// active state and to decide the toggle direction.
+export function hasStressAfterSelection(state: EditorState): boolean {
+  const { to } = state.selection;
+  const docSize = state.doc.content.size;
+  // Clamp to the doc size so a selection at the very end never reads past it.
+  const afterChar = state.doc.textBetween(to, Math.min(to + 1, docSize));
+  return afterChar === STRESS_ACCENT;
+}
+
+// Build a single transaction that toggles the stress accent after the
+// selection. One transaction => one undo step (Ctrl+Z reverts the toggle).
+export function toggleStressAccent(state: EditorState): Transaction {
+  const { from, to } = state.selection;
+  const tr = state.tr;
+
+  if (hasStressAfterSelection(state)) {
+    // Toggle off: drop the accent that immediately follows the letter.
+    tr.delete(to, to + 1);
+  } else {
+    // Toggle on: insertText inherits the marks at `to`, so the accent lands
+    // in the same text node as the letter and renders over it even when the
+    // letter is bold / italic / colored.
+    tr.insertText(STRESS_ACCENT, to);
+  }
+
+  // Restore the original selection so the accented letter stays highlighted
+  // and a re-click toggles the accent back off.
+  tr.setSelection(TextSelection.create(tr.doc, from, to));
+  return tr;
+}