[context menu] Ignore context menu mouseup on non-Mac platforms

[atomiks]

• I have followed (at least) the PR section of the contributing guide.

Fixes #3595

On Mac, context menus open on mousedown so they support the down -> move -> release up pattern for selection. On Windows it opens on mouseup, so that's irrelevant. I don't know about Linux, but I've just made it match Windows for simplicity.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/@base-ui/react@3944
  

  pnpm add https://pkg.pr.new/@base-ui/utils@3944
  

commit: aea36a2

[mui-bot]

Bundle size report

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+22B(0.00%)	🔺+2B(0.00%)

Details of bundle changes

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[greptile-apps]

Greptile Overview

Greptile Summary

This PR changes context-menu item mouseup handling to ignore right-click mouseup on non‑Mac platforms (matching Windows behavior), and updates tests by removing mouseup-driven closing scenarios while keeping coverage for ignoring mouseup at the initial spawn point.

The behavioral change lives in the shared menu-item hook (useMenuItemCommonProps), so it affects all menu item types used under ContextMenu roots, preventing unintended item activation/closure on Windows/Linux-style context menu interactions.

Confidence Score: 4/5

• This PR is reasonably safe to merge, with low functional risk confined to context-menu mouseup behavior.
• The change is small and scoped to a single event handler branch, and existing tests still cover the core “ignore mouseup at spawn point” regression. Main remaining risk is environment brittleness if detectBrowser reads browser globals at import time, which could impact SSR or non-browser tests.
• packages/react/src/menu/item/useMenuItemCommonProps.ts

Important Files Changed

Filename	Overview
packages/react/src/menu/item/useMenuItemCommonProps.ts	Adds a non-Mac guard to ignore right-click mouseup for context menus; potential brittleness if isMac touches browser globals at import time.
packages/react/src/context-menu/root/ContextMenuRoot.test.tsx	Removes mouseup-driven close tests and keeps tests for ignoring mouseup at spawn point; coverage for non-Mac behavior is reduced.

[greptile-apps]

_{2 files reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[mnajdova]

Let's add a test for non-Mac environment, just to be safe.

[LukasTy]

LGTM. 👍
Maybe @flaviendelangle could check the behavior on Linux?

[flaviendelangle]

When a context menu is open, right-clicking on an item inside the context menu immediately closes the menu instead of allowing the item to handle the right-click interaction.

If this is the bug, then I can't reproduce it on master and on this PR (Linux Mint - Chromium).

[michaldudak]

Looks OK on Windows.

[LukasTy]

When a context menu is open, right-clicking on an item inside the context menu immediately closes the menu instead of allowing the item to handle the right-click interaction.

If this is the bug, then I can't reproduce it on master and on this PR (Linux Mint - Chromium).

Thank you for checking. 🙏
Yes, and it looks like it was/is only reproducible on Windows. 👌