fix(hud): resolve overlay snap to primary on multi-monitor

[MohamedV0]

Summary

Fix the HUD overlay snapping to the primary monitor when recording
starts on a multi-monitor setup. The positioning logic now detects
which display the HUD is on using screen.getDisplayMatching()
instead of always defaulting to getPrimaryDisplay().

Context / Motivation

• On multi-monitor setups, users position the HUD on the external
  monitor (typically the screen being recorded)
• Clicking Record triggers a React re-render that swaps idle controls
  for recording controls, firing the ResizeObserver
• The ResizeObserver sends set-hud-overlay-compact-width and
  set-hud-overlay-measured-height IPC messages to the main process
• These handlers call applyHudOverlayBounds(), which computes x,y
  from the primary display's workArea — always re-centering on
  primary regardless of where the user placed the HUD
• The fix follows the same getDisplayMatching() pattern already
  used by getUpdateToastBounds() in this file

Changes

• [windows] Add getHudOverlayDisplay() helper that uses
  getDisplayMatching(hudWindow.getBounds()) with fallback to
  getPrimaryDisplay() when the window doesn't exist yet
• [windows] Replace getPrimaryDisplay() in getHudOverlayBounds()
• [windows] Replace getPrimaryDisplay() in
  set-hud-overlay-compact-width IPC handler
• [windows] Replace getPrimaryDisplay() in
  set-hud-overlay-measured-height IPC handler
• [windows] Replace getPrimaryDisplay() in
  createHudOverlayWindow() maxHeight constraint

Testing

• Manual testing on Windows 11 Pro dual-monitor setup
• Verified HUD stays on external monitor through recording
  start/stop cycle
• Verified dropdown expand/collapse on external monitor
• Verified single-monitor — zero behavior change
• Automated tests (N/A — Electron window positioning)

Manual test — Windows 11 Pro (Build 26200):

1. Built with npx vite build && npx electron-builder --win --dir
2. Moved HUD to external monitor (positioned left of primary)
3. Clicked Record — HUD stayed on external after countdown
4. Opened/closed dropdowns — HUD stayed on external
5. Stopped recording — HUD collapsed on external correctly
6. Diagnostic logging confirmed getDisplayMatching() returned
   the correct display throughout the entire cycle

Single monitor: getDisplayMatching() with one display
always returns that display — identical to getPrimaryDisplay().
No behavioral change.

Cross-platform: screen.getDisplayMatching() is a core Electron
API on Windows, macOS, and Linux. No platform-specific code added.

Risks & Impact

• No breaking changes
• No renderer or IPC protocol changes
• Single-monitor setups: zero behavioral difference
• getDisplayMatching() returns the display with largest overlap —
  same behavior as Electron's own transparent window positioning

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Improved HUD overlay positioning and sizing for multi-display setups. The HUD now correctly identifies which display it's on and adjusts layout accordingly, rather than always defaulting to the primary display, ensuring proper alignment and dimensions when using multiple monitors.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 49e50356-dc29-4e40-bcc8-c8d0baeb03fe

📥 Commits

Reviewing files that changed from the base of the PR and between 6703e6f and 0c5fa40.

📒 Files selected for processing (1)

• electron/windows.ts

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📝 Walkthrough

Walkthrough

The PR introduces getHudOverlayDisplay() to intelligently select the appropriate display for HUD layout calculations. When an HUD overlay window exists, the function uses the display matching the HUD's current bounds; otherwise, it falls back to the primary display. This selection logic is then applied across HUD positioning, sizing, and clamping operations.

Changes

Cohort / File(s)	Summary
HUD Display Selection & Sizing electron/windows.ts	Added getHudOverlayDisplay() function for intelligent display selection. Updated getHudOverlayBounds(), IPC handlers set-hud-overlay-compact-width and set-hud-overlay-measured-height, and createHudOverlayWindow() to use the selected display's bounds/workArea instead of always referencing the primary display.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• Fix Linux HUD input handling #157: Modifies createHudOverlayWindow() in the same file to adjust HUD mouse passthrough behavior, alongside the display selection changes in this PR.

Suggested labels

Checked

Poem

🐰 A HUD so smart, no longer tied,
To primary display's stubborn pride,
Now finds the screen where it should be,
Multi-monitor harmony! 🖥️✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: fixing HUD overlay snapping to primary monitor on multi-monitor setups.
Description check	✅ Passed	The PR description includes all key sections from the template: summary, motivation/context, detailed changes, comprehensive testing (including manual verification on dual-monitor setup), and risk assessment.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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