Fix windows overlapping across monitors

[biswadip-paul]

Summary

• Clamps visible window frames to monitor bounds after layout calculation in calculateCombinedLayoutUsingPools()
• Prevents tiled window frames from bleeding into adjacent monitors' screen space
• Hidden windows (already tracked in hiddenPool) are excluded from clamping since their positioning is handled separately by HiddenWindowPlacementResolver

Details

The Niri layout engine's calculateLayoutInto() produces window frames based on container positions and scroll offsets without enforcing monitor boundary constraints. When a visible container partially extends beyond the monitor's frame rect, individual window frames within it can bleed into neighboring monitor space.

The fix adds a post-layout clamping pass that intersects each visible window's frame with monitor.frame, removing frames that fall entirely outside the monitor bounds.

Test plan

• Open windows across two monitors — no window frame should extend beyond its assigned monitor
• Scroll through columns near monitor edges — partial columns should be clipped at the boundary
• Verify hidden windows still animate/position correctly (not affected by clamping)
• Existing centeredColumnsDoNotEmit*WorkspaceFramesAcross*MonitorBoundary tests continue to pass

Fixes #349

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Fixed a window layout issue where frames could extend beyond monitor boundaries. Visible windows are now clamped to their assigned monitor’s display area so they stay fully on-screen.
  • Removed or hidden any windows with no overlap after clamping, preventing orphaned off-screen entries and improving layout consistency across multi-monitor setups.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a90a772a-f8db-4105-ac67-a118b2843be7

📥 Commits

Reviewing files that changed from the base of the PR and between 47866ca and c489737.

📒 Files selected for processing (1)

• Sources/OmniWM/Core/Layout/Niri/NiriLayoutEngine+Animation.swift

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📝 Walkthrough

Walkthrough

Window layout calculation in NiriLayoutEngine+Animation.swift now clamps visible window frames to monitor bounds before returning layout results. A new helper method intersects non-hidden window frames with the monitor bounds, removing frames outside bounds and updating frames that partially extend beyond.

Changes

Window Bounds Clamping

Layer / File(s)	Summary
Monitor bounds clamping for visible windows Sources/OmniWM/Core/Layout/Niri/NiriLayoutEngine+Animation.swift	clampVisibleFramesToMonitorBounds(_:) intersects each visible window frame with monitor bounds, removes null intersections, and updates frames that changed. The method is invoked from calculateCombinedLayoutUsingPools after building framePool/hiddenPool to restrict frames before returning results.

Estimated Code Review Effort

🎯 3 (Moderate) | ⏱️ ~15 minutes

Poem

🐰 Frames that drift beyond the screen so wide,
Now clipped and bounded, safely tucked inside,
Each visible window meets the monitor line,
No stray corners peeking where they don't belong,
A tidy desktop hops along in time!

🚥 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 windows overlapping across monitors' directly and clearly summarizes the main change: addressing window overlap issues in multi-monitor setups, which is the core objective of the PR.
Linked Issues check	✅ Passed	The PR implements clamping of visible window frames to monitor bounds to prevent windows from overlapping across monitors, directly addressing the multi-monitor overlap issue reported in #349.
Out of Scope Changes check	✅ Passed	All changes are focused on fixing window overlap by clamping frames to monitor bounds; no unrelated modifications or out-of-scope work is present.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 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 `@Sources/OmniWM/Core/Layout/Niri/NiriLayoutEngine`+Animation.swift:
- Around line 470-476: The current for-in loop over framePool mutates framePool
(removing/updating entries) which is unsafe; instead, iterate framePool without
mutating it by collecting changes first: create a removal list (e.g.,
removeTokens) and an updates dictionary (e.g., updatedFrames), loop over
framePool where hiddenPool[token] == nil computing clamped, append token to
removeTokens if clamped.isNull, or record updatedFrames[token] = clamped if
clamped != frame, then after the loop apply removals
(framePool.removeValue(forKey:)) and updates (framePool[token] = clamped) to
framePool. Ensure you reference the same symbols: framePool, hiddenPool,
monitorBounds, token, frame, clamped, and perform all mutations only after the
iteration completes.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d55519b1-da37-4bad-ac22-bdbfadf09a3a

📥 Commits

Reviewing files that changed from the base of the PR and between 917e270 and 47866ca.

📒 Files selected for processing (1)

• Sources/OmniWM/Core/Layout/Niri/NiriLayoutEngine+Animation.swift

[biswadip-paul]

CodeRabbit's inline feedback on the unsafe dictionary mutation during iteration has been addressed in commit c489737 with the two-phase collect-then-apply approach. The follow-up review confirms no remaining actionable issues. LGTM — ready for maintainer review.