fix(macos): scale remote scroll input using macOS scroll speed

[martona]

Description

This fixes macOS remote scrolling being painfully slow in Sunshine.

Moonlight sends wheel deltas in WHEEL_DELTA = 120 units, including high-resolution sub-detent data. Sunshine’s macOS backend was converting that to CoreGraphics line scroll events on an integer basis with 120 -> 1 line, which both ignored high-res scroll granularity and made the macOS Mouse scroll speed setting effectively useless.

This changes macOS scoll behavior the following way:

• preserve high-resolution scroll input as pixel-unit CoreGraphics scroll events
• mark scroll events as continuous
• read com.apple.scrollwheel.scaling from global preferences
• treat it as the 0..1 Mouse scroll speed slider value
• map Apple’s default 0.3125 to 5 lines per detent
• log the raw and derived values at startup

Default scrolling now feels like it's alive, while lower and higher macOS scroll-speed settings still do what you’d expect.

Testing

Was tested with a full build (scripts/build_macos.sh) and verified manually on Tahoe.

Issues Fixed or Closed

Roadmap Issues

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Unit tests have been added or updated for any new or modified functionality

AI Usage

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Bundle Report

Bundle size has no change ✅

[codecov]

Codecov Report

❌ Patch coverage is 27.02703% with 27 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@15eabb2). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/platform/macos/input.cpp	27.02%	23 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #5133   +/-   ##
=========================================
  Coverage          ?   17.87%           
=========================================
  Files             ?      111           
  Lines             ?    24093           
  Branches          ?    10649           
=========================================
  Hits              ?     4307           
  Misses            ?    17322           
  Partials          ?     2464           

Flag	Coverage Δ
Archlinux	11.23% <ø> (?)
FreeBSD-amd64	13.36% <ø> (?)
Homebrew-ubuntu-22.04	13.58% <ø> (?)
Linux-AppImage	12.15% <ø> (?)
Windows-AMD64	14.89% <ø> (?)
Windows-ARM64	13.22% <ø> (?)
macOS-arm64	19.06% <27.02%> (?)
macOS-x86_64	18.41% <27.02%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/platform/macos/input.cpp	35.31% <27.02%> (ø)

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