feat(core): add visible focus ring support

[Pushtikansara]

Description

This PR connects the existing focus system with widget focus state so that focused widgets correctly render their focus ring.
##Changes
-Added focus and blur event handling in App.
-Synchronized widget isFocused state with FocusManager.
-Triggered widget re-rendering when focus changes.
-Added tests covering focus propagation and synchronization behavior.

Related Issue

Closes #325

Which package(s)?

@termuijs/core

Type of Change

• 🐛 Bug fix (type:bug)
• ✨ Feature (type:feature)
• 📝 Docs (type:docs)
• 🧪 Tests (type:testing)
• ♻️ Refactor (type:refactor)
• 🎨 Design / UX (type:design)
• ♿ Accessibility (type:accessibility)
• ⚡ Performance (type:performance)
• 🔧 DevOps / CI (type:devops)
• 🔒 Security (type:security)

Checklist

• ⭐ You starred the repo. The needs-star check blocks your merge otherwise.
• Tests pass locally: bun vitest run
• Build passes: bun run build
• Typecheck passes: bun run typecheck
• You read CONTRIBUTING.md.
• Your PR title follows type: short description.
• Widget state mutators call markDirty() (if your change affects rendering).
• No new any types without an inline comment explaining why.
• No unrelated refactors bundled into this PR.

GSSoC 2026 Participation

• You are a GSSoC 2026 contributor.
• Your GSSoC profile: https://gssoc.girlscript.org/profile/____
• https://gssoc.girlscript.org/profile/adc9e69c-a9de-4469-ba44-ed6de335d366

Screenshots / Recordings (UI changes)

N/A

Notes for the Reviewer

This change synchronizes widget focus state with FocusManager events and ensures focused widgets are re-rendered when focus changes. Tests have been added to verify focus state propagation and synchronization behavior.

Summary by CodeRabbit

• New Features
  • Implemented focus state tracking and propagation at the application level.
  • Focus-aware widgets now correctly reflect and update their state based on focus changes.
  • Focus changes automatically trigger re-renders and ensure proper synchronization with the widget lifecycle.

[github-actions]

Hi @Pushtikansara 👋

⭐ Star this repo before your PR merges.

Why? GSSoC 2026 contributors who star get priority review and points credit. After you star, push any commit (or re-run this check). The needs-star label lifts automatically.

Thanks for your contribution to TermUI.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds application-level focus tracking to App. It subscribes to FocusManager events, propagates isFocused state to focus-aware widgets during widget-tree traversal, and triggers re-renders when focus changes. Tests verify focus flag updates, dirty marking, and event synchronization across the widget lifecycle.

Changes

App-level focus tracking and propagation

Layer / File(s)	Summary
FocusAwareWidget contract and App focus lifecycle packages/core/src/app/App.ts	FocusAwareWidget interface defines widgets with id, isFocused, and optional markDirty. App adds _unsubFocus and _unsubBlur fields and subscribes to FocusManager focus/blur events in the constructor. mount() lazily re-establishes subscriptions if missing; unmount() cleans up listeners and nulls the callbacks.
Widget focus state propagation packages/core/src/app/App.ts	_walkWidget updates isFocused on focus-aware widgets based on focus.currentId. New private methods _handleFocusEvent, _setWidgetFocused, and _isFocusAwareWidget manage focus state updates, mark affected widgets dirty, and trigger requestRender() when focus changes.
Focus integration tests and test widget packages/core/src/app/App.test.ts	FocusTestWidget mock widget tracks focus state, render counts, and renders a focus marker (F vs -) to its screen. Helper factories createFocusTestRoot and createInteractiveTestOptions support building focusable test trees. Test suite verifies focus flag propagation, dirty/re-render cycles, and focus event synchronization before mount completes.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related issues

• feat(core): add focus ring indicators #325: The visible focus ring indicator feature would directly use this isFocused flag propagation and focus marker rendering to display focus state in the UI.

Suggested labels

gssoc:approved, type:feature, area:core, level:intermediate, type:testing

Suggested reviewers

• Karanjot786

Poem

🐰 Hop, hop! Focus flows so free,
App tracks where the cursor be,
Dirty marks and renders bright,
Widgets glow with focus light,
Tests confirm each little sight! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 3

❌ Failed checks (3 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The PR closes issue #296 which requires implementing a usePolling hook in packages/data. However, the actual changes are in packages/core (App.ts and App.test.ts) with no modifications to packages/data and no usePolling hook implementation.	The PR must implement the usePolling hook in packages/data per issue #296 requirements: create usePolling.ts, usePolling.test.ts, and export from packages/data/src/index.ts.
Out of Scope Changes check	⚠️ Warning	The PR makes changes only to packages/core, but the linked issue #296 requires all work to be confined to packages/data. The scope of this PR does not match the requirements of the linked issue.	Refactor the PR to implement usePolling hook in packages/data as specified in issue #296, and ensure no modifications occur outside packages/data per the AGENTS.md rules.
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat(core): add visible focus ring support' is highly related to the main change in the PR, which connects the focus system with widget focus state for focus ring rendering.
Description check	✅ Passed	The PR description includes all required sections with complete information: clear description, linked issue, package identification, type of change, comprehensive checklist completion, and GSSoC participation.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[github-actions]

🎉 Thanks for your first PR to TermUI, @Pushtikansara.

Before your PR merges:

1. ⭐ Star the repo. Required. The star-check job blocks your merge otherwise.
2. ✅ All checks green: build, test, typecheck.
3. 🏷 PR title follows type: short description. Example: fix: handle empty list.
4. 🔗 Link your closing issue in the description.

GSSoC 2026 points come from labels after merge:

• gssoc:approved. +50 base points.
• level:beginner / intermediate / advanced / critical. +20 / +35 / +55 / +80.
• quality:clean / exceptional. x 1.2 / x 1.5.
• type:*. Stackable bonus.

Your reviewer responds within 48 hours. Ping @Karanjot786 on Discord for urgent help.

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