Expose main content focus to tab chrome

[lawrencecchen]

Problem

Hosts can move keyboard focus to an adjacent surface while keeping Bonsplit selection alive, but the tab chrome has no way to de-emphasize its selected indicator.

Change

Add an optional isMainContentFocused input to BonsplitView and thread it through nested pane containers. The selected tab remains selected, while focused tab chrome is desaturated when the host reports that another surface owns input.

Validation

swift test --package-path vendor/bonsplit builds successfully. One existing translated geometry test was flaky in this run.

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Summary by cubic

Adds an isMainContentFocused input to BonsplitView so hosts can desaturate the selected tab chrome when keyboard focus moves to an adjacent surface.

• The selected tab remains selected; only the tab chrome de-emphasizes when the host reports another surface owns input.
• isMainContentFocused defaults to true, so existing callers are unaffected.

^{Written for commit de63f80. Summary will update on new commits.}

Summary by CodeRabbit

• New Features
  • Added an isMainContentFocused option to control whether the primary content receives keyboard focus while Bonsplit continues managing pane selection.
  • The option is available through both BonsplitView initializers and defaults to enabled.
  • Focus behavior is consistently applied across panes and nested split views.

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Reviewing files that changed from the base of the PR and between a708f09 and de63f80.

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• Sources/Bonsplit/Internal/Views/SplitContainerView.swift

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Configuration used: defaults

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📥 Commits

Reviewing files that changed from the base of the PR and between 4679197 and a708f09.

📒 Files selected for processing (5)

• Sources/Bonsplit/Internal/Views/PaneContainerView.swift
• Sources/Bonsplit/Internal/Views/SplitContainerView.swift
• Sources/Bonsplit/Internal/Views/SplitNodeView.swift
• Sources/Bonsplit/Internal/Views/SplitViewContainer.swift
• Sources/Bonsplit/Public/BonsplitView.swift

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📝 Walkthrough

Walkthrough

Bonsplit adds an isMainContentFocused option to its public view initializers. The value propagates through split containers to pane views. Pane focus now also requires main-content focus.

Changes

Main content focus control

Layer / File(s)	Summary
Focus option and view hierarchy wiring Sources/Bonsplit/Public/BonsplitView.swift, Sources/Bonsplit/Internal/Views/SplitViewContainer.swift, Sources/Bonsplit/Internal/Views/SplitNodeView.swift	BonsplitView exposes isMainContentFocused in both initializers. The value is stored and passed through the split view hierarchy.
Focus state application Sources/Bonsplit/Internal/Views/SplitContainerView.swift, Sources/Bonsplit/Internal/Views/PaneContainerView.swift	Split containers pass the focus state to panes and nested split containers. A pane is focused only when main-content focus is enabled and the pane matches the controller’s focused pane.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Feature

Suggested reviewers: austinywang

Merge Risk: ⚪ Minimal · up to a708f

The new option changes tab chrome when focus leaves the main content while preserving the selected tab.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: exposing main content focus so tab chrome can reflect focus state.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat-sidebar-focus-tab-state

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[lawrencecchen]

Superseded by #264, which combines this change with the other right sidebar Bonsplit change for manaflow-ai/cmux#15534.