[Editor] Incorrect word wrap for monospace CJK fonts

[MikeWang000000]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version:
  Version: 1.107.1 (system setup)
  Commit: 994fd12
  Date: 2025-12-17T14:15:14.850Z
  Electron: 39.2.3
  ElectronBuildId: 12895514
  Chromium: 142.0.7444.175
  Node.js: 22.21.1
  V8: 14.2.231.21-electron.0
  OS: Windows_NT x64 10.0.17763

• OS Version: Windows 10 1809

Steps to Reproduce:

1. Install a monospace Chinese font such as Maple Font: https://github.com/subframe7536/maple-font/releases/download/v7.9/MapleMonoNormalNL-CN.zip
2. Add the config to settings.json: "editor.fontFamily": "'Maple Mono Normal NL CN', 'Courier New', monospace"
3. Paste following words into the editor

   WORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORD
   文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字文字
   

4. Before word wrap:

5. Enable word wrap:

The horizontal scrollbar still exists. The line length for alphabets is correct, but is wrong for CJK characters.

[FredBill1]

Using "editor.wrappingStrategy": "advanced" and optionally "editor.wordBreak": "keepAll" seems to resolve this issue. see #154263 (comment)

[MikeWang000000]

Using "editor.wrappingStrategy": "advanced" and optionally "editor.wordBreak": "keepAll" seems to resolve this issue. see #154263 (comment)

Thanks for the work around!

I read through the code and found VSCode was testing '\uff4d' (ｍ, fullwidth Latin small letter m) to get the width of a fullwidth character.

vscode/src/vs/editor/browser/config/fontMeasurements.ts

Lines 171 to 183 in b40b1db

	const typicalHalfwidthCharacter = this._createRequest('n', CharWidthRequestType.Regular, all, monospace);
	const typicalFullwidthCharacter = this._createRequest('\uff4d', CharWidthRequestType.Regular, all, null);
	const space = this._createRequest(' ', CharWidthRequestType.Regular, all, monospace);
	const digit0 = this._createRequest('0', CharWidthRequestType.Regular, all, monospace);
	const digit1 = this._createRequest('1', CharWidthRequestType.Regular, all, monospace);
	const digit2 = this._createRequest('2', CharWidthRequestType.Regular, all, monospace);
	const digit3 = this._createRequest('3', CharWidthRequestType.Regular, all, monospace);
	const digit4 = this._createRequest('4', CharWidthRequestType.Regular, all, monospace);
	const digit5 = this._createRequest('5', CharWidthRequestType.Regular, all, monospace);
	const digit6 = this._createRequest('6', CharWidthRequestType.Regular, all, monospace);
	const digit7 = this._createRequest('7', CharWidthRequestType.Regular, all, monospace);
	const digit8 = this._createRequest('8', CharWidthRequestType.Regular, all, monospace);
	const digit9 = this._createRequest('9', CharWidthRequestType.Regular, all, monospace);

However fullwidth Latin letters is missing in Maple Font. They all fell back to the default font so the fullwidth character width was miscalculated.