fix(core): invalidate overlay layers and reset screen state on resize

[ionfwsrijan]

Description

Two coordinated bugs caused overlay content (modals, dropdowns, toasts) to permanently disappear after terminal resize:

Fix 1: LayerManager.resize() — Invalidate all layers

Changed dirtyRegion = null to dirtyRegion = { x: 0, y: 0, width: cols, height: rows } so every layer is fully recomposited after resize (LayerManager.ts:258-261).

Fix 2: Screen.resize() — Reset all ancillary state

Added reset of _previousStyleLines, _clipStack, _translateYStack, _translateY, _ansiQueue, _flushEpoch, _swapping, and _backdropFilters to prevent stale state from causing clipping/translation/swap errors after resize (Screen.ts:433-446).

Tests

• Updated LayerManager.test.ts to verify dirtyRegion covers the full new dimensions after resize and that compositing works post-resize.
• Added Screen.test.ts test verifying all ancillary state is reset after resize.

Closes #1911

Summary by CodeRabbit

• Bug Fixes
  • Resizing now fully refreshes terminal layers so content is redrawn correctly after a size change.
  • Resizing the screen now clears leftover rendering state, preventing clipping, translation, or queued output from affecting new content.
  • Content entered after a resize now renders properly using the updated terminal dimensions.

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 839fe1f6-b016-4387-b16a-170fe95833f1

📥 Commits

Reviewing files that changed from the base of the PR and between 2dad0f8 and 9423c85.

📒 Files selected for processing (1)

• packages/core/src/terminal/LayerManager.test.ts

📝 Walkthrough

Walkthrough

LayerManager.resize() now sets each layer's dirtyRegion to the full new grid dimensions instead of null, ensuring compositing rerenders all layers after resize. Screen.resize() additionally clears clip/translate stacks, ANSI queue, style fingerprints, flush epoch, swap flag, and backdrop filters. Tests are updated accordingly.

Resize State Reset Fix

Layer / File(s)

Summary

LayerManager and Screen resize fixes + tests packages/core/src/terminal/LayerManager.ts, packages/core/src/terminal/Screen.ts, packages/core/src/terminal/LayerManager.test.ts, packages/core/src/terminal/Screen.test.ts

LayerManager.resize() sets dirtyRegion to {x:0, y:0, width:cols, height:rows} instead of null; Screen.resize() clears _previousStyleLines, _clipStack, _translateYStack, _translateY, _ansiQueue, _flushEpoch, _swapping, and _backdropFilters. Tests replace the old "clears dirty region" assertion with full-grid dirty checks and composite correctness, and add a new Screen test verifying all ancillary state is reset.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Karanjot786/TermUI#694: Adjusts LayerManager dirty-region and resize unit-test coverage, directly overlapping with this PR's test changes.
• Karanjot786/TermUI#1184: Changes LayerManager's dirtyRegion handling so resized layers are marked dirty across full bounds rather than cleared to null.
• Karanjot786/TermUI#1856: Introduces _backdropFilters in Screen.ts, which this PR now clears in Screen.resize().

Suggested labels

gssoc:approved, quality:clean, type:bug, level:intermediate

Suggested reviewers

• Karanjot786

Poem

🐇 A resize once made overlays flee,
dirtyRegion set to null — oh me!
Now the whole grid is marked as changed,
clips and queues are all rearranged.
Modals stay put, as they should be! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise, specific, and accurately summarizes the resize-state fix.
Description check	✅ Passed	The description covers the bug, fix, tests, and linked issue, though several template sections are left unfilled.
Linked Issues check	✅ Passed	The changes satisfy #1911 by invalidating layers on resize, resetting screen state, and adding tests for both behaviors.
Out of Scope Changes check	✅ Passed	The PR stays focused on resize handling and related tests, with no clear unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/core/src/terminal/LayerManager.test.ts`:
- Around line 331-343: The resize composition test in LayerManager.test.ts is
using require() to construct Screen even though the file runs as ESM, so replace
that usage with the already imported Screen symbol in the composite test. Keep
the rest of the resize assertions intact and ensure the test instantiates Screen
directly before calling lm.composite(screen).

In `@packages/core/src/terminal/Screen.test.ts`:
- Around line 73-93: The resize test in Screen.test is not actually seeding the
saved-line caches, so it can pass even if Screen.resize stops clearing them.
Update the Screen resize test by populating the back buffer, invoking
saveLines(), and then asserting that both getPreviousLine(0) and
getPreviousStyleLine(0) are empty after resize; keep the existing checks around
resize, activeClip, and the Screen state helpers.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: a61e2b1f-88c5-4576-a6f3-6c951998dea0

📥 Commits

Reviewing files that changed from the base of the PR and between 85e8d36 and 2dad0f8.

📒 Files selected for processing (4)

• packages/core/src/terminal/LayerManager.test.ts
• packages/core/src/terminal/LayerManager.ts
• packages/core/src/terminal/Screen.test.ts
• packages/core/src/terminal/Screen.ts

[ionfwsrijan]

@Karanjot786 Please review this