fix: prevent crash on sidebar hover

[apollo880]

Fixes #750

Summary

Implemented a targeted fix to prevent crashes when hovering the sidebar/titlebar top control cluster.

Root-cause hypothesis

WindowDragHandleView participated in hit-testing during passive hover/cursor events (mouseMoved, cursorUpdate, etc.). That code path performs complex top-hit/sibling hit-tests intended for drag capture, and it was being exercised on mere pointer motion over titlebar controls.

Changes

• In WindowDragHandleView.DraggableView.hitTest(_:), added a gate to return nil for passive event types.
• Kept existing drag-handle capture logic for click/drag events.

Co-authored-by: Codex noreply@openai.com
Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

Summary by CodeRabbit

• Bug Fixes
  • Enhanced window titlebar responsiveness by optimizing event handling for mouse interactions, including movement and hover states.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 4d9587c and 2fbaf93.

📒 Files selected for processing (1)

• Sources/WindowDragHandleView.swift

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📝 Walkthrough

Walkthrough

Adds a guard condition to WindowDragHandleView's hit-testing logic that skips processing for passive/hover-related events such as mouseMoved, cursorUpdate, mouseEntered, mouseExited, and flagsChanged. A helper function shouldParticipateInHitTesting(for:) determines whether to proceed with hit-testing based on event type.

Changes

Cohort / File(s)	Summary
Event Hit-Testing Guard Sources/WindowDragHandleView.swift	Adds early-return guard in hitTest to skip passive/hover events (mouseMoved, cursorUpdate, mouseEntered, mouseExited, flagsChanged, appKitDefined, systemDefined, applicationDefined, periodic); introduces helper method shouldParticipateInHitTesting(for:) to evaluate event eligibility for hit-testing participation.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related issues

• cmux shutdowns when move mouse pointer at sidebar top button group #750 — Directly addresses the reported crash when moving the mouse pointer over the sidebar button group by preventing passive hover events from triggering reentrant hit-testing.
• Crash on hover: Fatal access conflict in WindowDragHandleView.hitTest #723 — Similar hover-triggered reentrant crash in WindowDragHandleView.hitTest that appears to be resolved by the same fix pattern.

Possibly related PRs

• Fix exclusive-access crash in WindowDragHandleView hitTest #736 — Modifies WindowDragHandleView's hitTest with an early-return guard for non-interactive events, implementing the same mitigation strategy.
• Fix drag-handle crash on launch from stale foreign-window events #620 — Updates WindowDragHandleView.swift hit-testing logic with guards around passive/event-type processing.

Poem

🐰 A mouse moved across the sidebar's edge,
But now it glides without a pledge—
No hit-tests fired, no crashes feared,
The draggable view's bug is cleared!
Passive events know their place,
And stability wins the race. ✨

🚥 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%.	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 'fix: prevent crash on sidebar hover' directly addresses the primary change - fixing crashes when hovering the sidebar/titlebar by preventing passive events from participating in hit-testing.
Linked Issues check	✅ Passed	The PR successfully implements the required fix for issue #750 by preventing crashes on sidebar hover through targeted hit-testing logic for passive event types.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the sidebar hover crash issue; no unrelated modifications are present.

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[greptile-apps]

Greptile Summary

This PR implements a targeted fix to prevent crashes during sidebar/titlebar hover interactions. The root cause was that WindowDragHandleView.DraggableView.hitTest(_:) was executing complex drag-handle capture logic even for passive events like mouse movements and cursor updates.

Key changes:

• Added shouldParticipateInHitTesting(for:) method to filter out passive event types
• Modified hitTest(_:) to return nil early for passive events (mouseMoved, cursorUpdate, mouseEntered, mouseExited, etc.)
• Preserved existing drag-handle capture behavior for click/drag interactions
• Added debug logging for the new code path

The fix is minimal, well-reasoned, and directly addresses the crash without affecting drag functionality.

Confidence Score: 5/5

• This PR is safe to merge with no risk
• The fix is minimal (23 lines), well-targeted, and follows established AppKit patterns. It adds a simple guard condition that prevents crash-inducing code paths during passive events while preserving all drag functionality. The implementation uses standard NSEvent type checking and includes appropriate debug logging.
• No files require special attention

Important Files Changed

Filename	Overview
Sources/WindowDragHandleView.swift	Added early return in hitTest(_:) for passive events (hover, cursor updates) to prevent unnecessary complex hit-testing logic that was causing crashes

_{Last reviewed commit: 2fbaf93}

[teamleaderleo]

Thanks for this! The sidebar hover crash fix landed on main in #736, so main covers it now. Closing.