Proposal: Integrate Microsoft CalcManager as calculation engine backend

[dongfengweixiao]

Summary

I would like to propose integrating Microsoft Calculator's CalcManager as the backend calculation engine for the COSMIC calculator project. This change would leverage Microsoft's mature, extensively-tested calculation logic while maintaining the native COSMIC desktop experience.

Motivation

The current COSMIC calculator provides a solid user experience for the desktop environment. However, adopting Microsoft's CalcManager could offer several significant benefits:

1. Proven Reliability: Microsoft CalcManager has been battle-tested across millions of Windows installations and handles edge cases in arithmetic operations with high reliability.
2. Feature Completeness: CalcManager provides: - Infinite precision for basic arithmetic operations
   • Advanced scientific calculations
   • Programmer calculator functionality
   • Date calculations
   • Unit conversions
3. Active Maintenance: Microsoft actively maintains and improves the CalcManager codebase, ensuring bug fixes and performance improvements.

Evidence of Feasibility

A concrete example demonstrates that this integration is viable:

• Project: dongfengweixiao/calculator
• Architecture: Flutter frontend + CalcManager backend via FFI
• Platform: Successfully works on Linux (among other platforms)
• Features: Implements standard, scientific, and programmer modes with full CalcManager functionality

This project serves as a reference implementation showing that CalcManager can be effectively integrated into cross-platform applications, including Linux environments.

Migration Strategy

Phase 1: Proof of concept with basic operations
Phase 2: Full feature parity with current implementation
Phase 3: Enhanced features leveraging CalcManager capabilities

Potential Challenges

• Integration Complexity: Bridging Rust frontend with C#/C++ CalcManager may require FFI or wrapper development
• Dependencies: Managing CalcManager build dependencies within the COSMIC build system
• License Compatibility: CalcManager uses MIT license (compatible with GPL-3.0)

Community Impact

This integration would:

• Improve calculation accuracy and reliability
• Enable advanced calculator modes without reinventing the wheel
• Benefit from ongoing Microsoft improvements
• Potentially reduce maintenance burden on the COSMIC team

References

• Microsoft Calculator Repository
• Reference Implementation on Linux
• CalcManager

I would appreciate the community's feedback on this proposal.

[eandmsz]

I would love to see the wincalc_engine getting used. There are so many things that can go wrong with a calculator.
For example KDEs' kcalc has many bugs like: √(-2) results in 1.41, or 1+2 will show 3 on the results, and then you put in a x3 and you would expect 3x3 to be 9, but suddenly the whole 1+2x3 will be calculated instead and result 7.

Please use something proven and working.

[dongfengweixiao]

I would love to see the wincalc_engine getting used. There are so many things that can go wrong with a calculator. For example KDEs' kcalc has many bugs like: √(-2) results in 1.41, or 1+2 will show 3 on the results, and then you put in a x3 and you would expect 3x3 to be 9, but suddenly the whole 1+2x3 will be calculated instead and result 7.

Please use something proven and working.

These problems do not exist in the CalcManager.

[dongfengweixiao]

I would love to see the wincalc_engine getting used. There are so many things that can go wrong with a calculator. For example KDEs' kcalc has many bugs like: √(-2) results in 1.41, or 1+2 will show 3 on the results, and then you put in a x3 and you would expect 3x3 to be 9, but suddenly the whole 1+2x3 will be calculated instead and result 7.

Please use something proven and working.

I attempted to utilize Rust FFI to invoke CalcManager, and subsequent testing has confirmed the feasibility of this approach. You might consider migrating the backend of the calculator to this method.

2026-03-13.21-19-28.mp4

[kleenleen]

cosmic apps aim to be using rust backends though.