fix(core): reset _previousLines on Screen.resize() to prevent stale diff renderer state after terminal resize

[ionfwsrijan]

Description

When the terminal is resized, Screen.resize() creates fresh front/back grids but leaves _previousLines (the diff renderer's line cache) untouched. After a resize making the terminal smaller, stale content from the pre-resize grid remains in _previousLines, causing the diff renderer to skip rows whose current content happens to match the stale cached strings.

Root Cause

The resize() method recreated the front/back buffers but did not clear _previousLines.

Fix

Added this._previousLines = []; at the end of resize() to force a full re-render after terminal resize.

Changes

• packages/core/src/terminal/Screen.ts:306 — reset _previousLines on resize

Closes #681

Summary by CodeRabbit

• Bug Fixes
  • Resolved an issue where terminal display content would not refresh correctly following a screen resize operation.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 4d2d3ec2-a42a-4668-9544-77e0b37f8c9b

📥 Commits

Reviewing files that changed from the base of the PR and between c36cc8c and 592fe41.

📒 Files selected for processing (1)

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

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📝 Walkthrough

Walkthrough

This PR fixes a bug in the terminal screen resize logic. When the terminal is resized, the Screen.resize() method now clears the _previousLines cache by resetting it to an empty array, ensuring the diff renderer will not use stale pre-resize line content on the next render cycle.

Changes

Screen Resize Diff Cache Invalidation

Layer / File(s)	Summary
Invalidate previous lines cache on resize packages/core/src/terminal/Screen.ts	Screen.resize() resets _previousLines to an empty array to invalidate stale back-buffer line snapshots accumulated before the resize, preventing diff renderer corruption when terminal size changes.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A line once lost in the buffer cache,
Now cleared when the window takes a leap,
Fresh grids spring forth with pristine grace,
No phantom rows in resize's sweep! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly and concisely describes the main change: resetting _previousLines on Screen.resize() to fix stale diff renderer state after terminal resize.
Description check	✅ Passed	The PR description comprehensively explains the problem, root cause, and fix, with a clear reference to the related issue #681. All key template sections are adequately filled.
Linked Issues check	✅ Passed	The code change directly addresses the requirement in issue #681 by adding the suggested fix to reset _previousLines in the resize() method, matching the proposed solution.
Out of Scope Changes check	✅ Passed	The single-line change to packages/core/src/terminal/Screen.ts is directly scoped to addressing the stale diff renderer state issue described in issue #681 with no extraneous modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[github-actions]

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

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[ionfwsrijan]

@Karanjot786 You may review and merge

[Karanjot786]

Thank you so much for your contribution, @ionfwsrijan!

Your PR #690 fixed Screen.resize() to reset _previousLines. The diff renderer no longer shows stale output after a terminal resize.

Keep contributing. We appreciate your work.