Suggestions for Modernizing a Large Legacy Delphi Desktop Application [closed]

I’m currently exploring modernization strategies for a large Delphi-based desktop application that has been developed and maintained for over 20 years. We're running into increasing issues that make further development unsustainable: Key Challenges: High maintenance cost due to legacy codebase. RAD Studio licensing costs. Niche technology — limited community support and very difficult to find replacement developers. Highly complex code that requires serious refactoring. Multiple auxiliary applications (for license management, macros, rendering, etc.) are tightly coupled with the core Delphi app, increasing the complexity of any changes. Given these issues, I’m exploring two broad approaches to modernization: Option 1: Rewrite from Scratch Change the technology stack to something more modern and mainstream (e.g., C#, .NET, Java, or even full web stack with React/Node.js). Use GPTs or AI-assisted tooling to help accelerate the conversion process from Delphi to a modern language. Modularize the architecture with proper interfaces and separation of concerns, allowing parallel development by multiple teams. Option 2: Gradual Modernization with Coexisting Modules Keep the Delphi shell app as the host and integrate new functionality gradually using modern UI technologies. Example: Use React for frontend rendering, possibly with OpenGL/WebGL for 3D rendering. Explore server-side rendering with React or other modern frameworks (e.g., similar to DevExpress architecture). Replace screens or modules incrementally without the user noticing the backend switch. Long term, this may allow bundling as a web-based application or even inside Electron for desktop distribution. Additional Notes: The current app includes macro support and 3D rendering, so the modernization strategy needs to consider these. Eventually, we’d like the architecture to be more maintainable and scalable — with proper CI/CD, automated testing, and modular deployments. What I'm Looking For: Has anyone gone through a similar modernization of a Delphi application? What approaches or tech stacks worked for you? Are there any tools that help in converting Delphi codebases to more modern stacks (e.g., C#, Java)? Any pros/cons for full rewrite vs. hybrid coexistence? I’d appreciate any insights, shared experiences, or recommended tools. Thanks!

May 26, 2025 - 23:10

I’m currently exploring modernization strategies for a large Delphi-based desktop application that has been developed and maintained for over 20 years. We're running into increasing issues that make further development unsustainable:

Key Challenges: High maintenance cost due to legacy codebase.

RAD Studio licensing costs.

Niche technology — limited community support and very difficult to find replacement developers.

Highly complex code that requires serious refactoring.

Multiple auxiliary applications (for license management, macros, rendering, etc.) are tightly coupled with the core Delphi app, increasing the complexity of any changes.

Given these issues, I’m exploring two broad approaches to modernization:

Option 1: Rewrite from Scratch Change the technology stack to something more modern and mainstream (e.g., C#, .NET, Java, or even full web stack with React/Node.js).

Use GPTs or AI-assisted tooling to help accelerate the conversion process from Delphi to a modern language.

Modularize the architecture with proper interfaces and separation of concerns, allowing parallel development by multiple teams.

Option 2: Gradual Modernization with Coexisting Modules Keep the Delphi shell app as the host and integrate new functionality gradually using modern UI technologies.

Example: Use React for frontend rendering, possibly with OpenGL/WebGL for 3D rendering.

Explore server-side rendering with React or other modern frameworks (e.g., similar to DevExpress architecture).

Replace screens or modules incrementally without the user noticing the backend switch.

Long term, this may allow bundling as a web-based application or even inside Electron for desktop distribution.

Additional Notes: The current app includes macro support and 3D rendering, so the modernization strategy needs to consider these.

Eventually, we’d like the architecture to be more maintainable and scalable — with proper CI/CD, automated testing, and modular deployments.

What I'm Looking For:

Has anyone gone through a similar modernization of a Delphi application?

What approaches or tech stacks worked for you?

Are there any tools that help in converting Delphi codebases to more modern stacks (e.g., C#, Java)?

Any pros/cons for full rewrite vs. hybrid coexistence?

I’d appreciate any insights, shared experiences, or recommended tools. Thanks!