layout: backport primary side bar width fix to 1.137

[Lee Murray (mrleemurray)]

Backports #334864 to release/1.137.

Changes

• Preserve the user-set primary side bar width when toggling it with the side bar on the right.
• Redistribute split-view changes according to layout priority.
• Add a regression test covering Primary Side Bar width resets after toggling visibility (CTRL + B) #334167.

Validation

• npm run hygiene
• npm run transpile-client
• ./scripts/test.sh --run src/vs/base/test/browser/ui/splitview/splitview.test.ts — 19 passing

Local environment notes

• npm run compile-client was attempted but the worktree lacks the unrelated built-in extension dependency @vscode/markdown-editor.
• npm run typecheck-client was attempted but the worktree lacks the unrelated runtime type dependencies original-fs and electron.

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

Benjamin Christopher Simmonds (@benibenj)

Matched files:

• src/vs/base/browser/ui/splitview/splitview.ts

[Copilot]

🟢 Approval recommended

The backport matches the original fix and includes focused regression coverage.

Pull request overview

Backports the primary side bar width fix from #334864 to release 1.137.

Changes:

• Redistributes split-view changes by layout priority.
• Adds regression coverage for right-side primary side bar toggling.

File summaries

File	Description
src/vs/base/browser/ui/splitview/splitview.ts	Applies priority-aware relayout after constraint changes.
src/vs/base/test/browser/ui/splitview/splitview.test.ts	Tests width preservation during visibility toggles.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

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