feat(FactSystem): update Facts on unit changes

[rubenp02]

Description

FactMetaData now observes the corresponding UnitsSettings Fact and notifies existing Fact instances when it changes, refreshing cooked values, ranges, and units.

Before, unit changes made during Initial Setup prompted users to restart QGroundControl, disrupting the first-run UX. Unit settings now take effect immediately and no longer require a restart.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)
• CI/Build changes
• Other

Testing

• Tested locally
• Added/updated unit tests
• Tested with simulator (SITL)
• Tested with hardware

Platforms Tested

• Linux
• Windows
• macOS
• Android
• iOS

Checklist

• I have read the Contribution Guidelines
• I have read the Code of Conduct
• My code follows the project's coding standards
• I have added tests that prove my fix/feature works
• New and existing unit tests pass locally

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By submitting this pull request, I confirm that my contribution is made under the terms of the project's dual license (Apache 2.0 and GPL v3).

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[codecov]

Codecov Report

❌ Patch coverage is 73.91304% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 34.59%. Comparing base (f29efd3) to head (26c8be1).
⚠️ Report is 346 commits behind head on master.

Files with missing lines	Patch %	Lines
src/FactSystem/Fact.cc	62.50%	0 Missing and 3 partials ⚠️
src/FactSystem/FactMetaData.cc	80.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #15006      +/-   ##
==========================================
+ Coverage   25.47%   34.59%   +9.12%     
==========================================
  Files         769      945     +176     
  Lines       65912    85595   +19683     
  Branches    30495    39445    +8950     
==========================================
+ Hits        16788    29609   +12821     
+ Misses      37285    36326     -959     
- Partials    11839    19660    +7821     

Flag	Coverage Δ
unittests	34.59% <73.91%> (+9.12%)	⬆️

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

Files with missing lines	Coverage Δ
src/FactSystem/Fact.h	83.33% <ø> (+8.33%)	⬆️
src/FactSystem/FactMetaData.h	80.32% <ø> (-1.03%)	⬇️
src/Settings/UnitsSettings.cc	33.11% <ø> (+4.99%)	⬆️
src/FactSystem/Fact.cc	37.42% <62.50%> (+11.35%)	⬆️
src/FactSystem/FactMetaData.cc	42.76% <80.00%> (+7.29%)	⬆️

... and 654 files with indirect coverage changes

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[github-actions]

Build Results

Platform Status

Platform	Status	Details
Linux	Passed	View
Windows	Passed	View
MacOS	Passed	View
Android	Passed	View

All builds passed.

Pre-commit

Check	Status	Details
pre-commit	Failed (non-blocking)	View

Pre-commit hooks: 2 passed, 75 failed, 7 skipped.

Test Results

linux-coverage-integration: 51 passed, 0 skipped
linux-coverage-unit: 184 passed, 0 skipped
linux-sanitizers-integration: 30 passed, 0 skipped
linux-sanitizers-unit: 184 passed, 0 skipped
Total: 449 passed, 0 skipped

Code Coverage

Coverage: 70.6%

No baseline available for comparison

Artifact Sizes

Artifact	Size
QGroundControl	253.07 MB
QGroundControl-aarch64	176.99 MB
QGroundControl-installer-AMD64	138.07 MB
QGroundControl-installer-AMD64-ARM64	80.59 MB
QGroundControl-installer-ARM64	109.35 MB
QGroundControl-linux	84.75 MB
QGroundControl-mac	84.74 MB
QGroundControl-x86_64	189.24 MB
No baseline available for comparison

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_{Updated: 2026-08-31 16:27:27 UTC • Commit: 26c8be1 • Triggered by: Linux}