Add a crisp font-rendering option for macOS terminals

[Anthony Kim (anthonykim1)]

• Add terminal.integrated.fontRendering on macOS with inherit (default) and crisp.
• Opt into pixel-level antialiasing for high-DPI terminal text without changing the editor, sidebar, theme colors, font family, size, or weight. Other displays continue to inherit the workbench font policy.
• Apply the terminal style before WebGL initialization and clear cached glyphs after the style changes, so existing text updates without clearing the buffer or reloading the window.
• Reuse the same helper for normal, detached, and sticky-scroll terminals. Detached updates continue through the existing centralized configuration listener.
• Add coverage for the unchanged default, initial attachment, live mode changes, cache-refresh ordering, unchanged font/theme options, and detached terminals.

The rendering comparison pointed to font-smoothing policy as the significant appearance difference. This is an opt-in style preference, not a new renderer or an increase in resolution. The separate xterm alpha-blending experiment, texture-filtering changes, native-renderer ideas, and demo color overrides are intentionally outside this PR; no xterm dependency or source changes are required.

Validation

• GOMAXPROCS=2 npm run transpile-client
• GOMAXPROCS=2 npm run typecheck-client
• VSCODE_SKIP_PRELAUNCH=1 ./scripts/test.sh --run vs/workbench/contrib/terminal/test/browser/xterm/xtermTerminal.test — 24 passing.
• Targeted ESLint for the changed TypeScript files and stylelint for terminalFontRendering.css.

Manual review cases

1. On a macOS HiDPI display, compare inherit and crisp using the same font and theme in panel/editor terminals. Check that surrounding workbench text and terminal colors do not change.
2. Toggle the mode with text already visible. The glyph appearance should update without clearing terminal content; sticky-scroll and detached terminal output should follow the same policy.
3. Check a lower-DPI display or move the terminal between displays: crisp should not force pixel antialiasing below the existing HiDPI threshold.

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Inspirations from:

• The HiDPI policy comes from the existing workbench.fontAliasing CSS, applied to the terminal element rather than the entire workbench.
• The cache-refresh API comes from XtermTerminal.forceRedraw. Cached glyphs need to be regenerated after changing their inherited rendering policy.
• Detached-terminal update ordering follows TerminalService._ensureDetachedTerminalListeners, without introducing another listener for every detached instance.
• The CSS-to-rasterization behavior is informed by Chromium's CanvasRenderingContext2D::ResolveFont, which resolves the font using the canvas element's computed style, and xterm's TextureAtlas._drawToCache, which attaches the raster canvas to the terminal.

[Copilot]

Copilot review overview

🟡 Changes recommended

The platform-gated configuration contract is inaccurate, and detached forwarding is not actually covered by the new test.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review tier: Balanced
Findings: 1 · 1

New issues introduced by this change (2)

Severity	Finding
	src/​vs/​workbench/​contrib/​terminal/​common/​terminal.ts — Model the excluded setting as optional
	src/​vs/​workbench/​contrib/​terminal/​test/​browser/​xterm/​xtermTerminal.test.ts — Exercise detached configuration forwarding

What changed in this PR

Adds an opt-in crisp font-rendering mode for macOS terminals while preserving existing defaults.

Changes:

• Registers terminal.integrated.fontRendering.
• Applies smoothing consistently to standard, detached, and sticky-scroll terminals.
• Refreshes glyph caches and adds targeted tests.

File	Description
terminalStickyScrollOverlay.ts	Applies rendering policy to sticky scroll.
xtermTerminal.test.ts	Tests rendering configuration behavior.
terminalConfiguration.ts	Registers the setting.
terminal.ts (workbench)	Adds the configuration property.
xtermTerminal.ts	Applies rendering during attachment and updates.
terminalFontRendering.ts	Implements class updates and atlas refresh.
terminalFontRendering.css	Defines HiDPI smoothing behavior.
terminal.ts (platform)	Adds the setting identifier.

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