Source: Dev.to

Migrating a Desktop Product to SaaS – Preserving Inter‑Process Interactions

We have a desktop product that customers actively use, and we want to migrate toward a SaaS offering. In practice, that means we need backwards compatibility while we ship new features.

During that transition you often end up in a hybrid state: a desktop shell still exists, but more and more UI and logic moves into web technology (for example, hosted inside WebView2).

That hybrid state introduces a core challenge: how do you preserve everyday interactions across boundaries?
Drag & drop, keyboard copy/paste, focus, selection, and other “it just works” behaviours tend to break the moment parts of the UI live in different browsing contexts (iframes/windows) or even in a host process.

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Demo

• Repo (reference implementation):
• Live demo:

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Incremental Delivery via Explicit Boundaries

A pragmatic way to do incremental delivery is to introduce new modules behind explicit boundaries:

• Embed legacy / new pieces via iframe.
• Split experiences into separate windows when the host is desktop (or when multi‑monitor workflows help).
• Use Web Components to build reusable UI pieces without betting on a single framework.

The next question becomes: how do those pieces communicate so interactions (drag & drop, keyboard copy/paste) still work across boundaries? And how does it bridge to the desktop host?

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Architecture Overview

+------------------------ Desktop host (WebView2) ------------------------+
| WebMessageReceived  

- **WebView2 security**:  
  

- **Frames in WebView2**:  
  

- **Demo repository**: