Qt Framework UI Extraction: Modernizing Embedded Systems for the Web

Your industrial HMI (Human Machine Interface) is likely a hostage. Whether it’s running on a medical device, an automotive dashboard, or a factory floor controller, the Qt-based UI that was cutting-edge in 2014 is now a liability. The C++ developers who built it have moved on, the documentation is non-existent, and the business is demanding a cloud-connected, responsive web interface.

The traditional path is a "rip and replace" strategy—a manual rewrite that, according to Replay's analysis, has a 70% failure rate in enterprise environments. For embedded systems, this failure is often due to the "logic leakage" where UI and business logic are so tightly coupled in C++ that unravelling them feels like performing surgery with a sledgehammer.

Framework extraction modernizing embedded systems requires a shift from manual code translation to visual reverse engineering. Instead of reading thousands of lines of legacy QML or C++ Widgets code, we can now capture the intended user experience directly from the running application and transform it into a modern React-based architecture.

TL;DR: Modernizing legacy Qt embedded systems manually takes 18–24 months and costs millions. By using Replay, enterprises can achieve framework extraction modernizing embedded UIs in weeks by converting video recordings of legacy workflows into documented React components, saving 70% of development time and reducing the cost per screen from 40 hours to just 4 hours.

The High Cost of the "Qt Wall"#

Embedded systems are uniquely difficult to modernize. Unlike a standard Java backend, a Qt application is often tied to specific hardware, custom drivers, and real-time constraints. When you decide to move that UI to the web, you aren't just changing a language; you're changing an entire paradigm.

Industry experts recommend moving away from monolithic C++ UI layers toward a decoupled architecture. However, the $3.6 trillion global technical debt often keeps teams stuck. With 67% of legacy systems lacking any usable documentation, developers spend more time "archaeologizing" old C++ headers than actually building new features.

Visual Reverse Engineering is the process of capturing the visual output and behavioral flows of a legacy application to automatically generate modern code, bypassing the need for original source code or outdated documentation.

Why Manual Rewrites Fail#

The average enterprise rewrite takes 18 months. In the embedded world, this is often an underestimate. When you attempt manual framework extraction modernizing embedded systems, you encounter three primary friction points:

1. •State Synchronization: Replicating complex C++ state machines in Redux or Zustand is error-prone.
2. •Asset Loss: Original design files (PSDs, AI files) for legacy Qt apps are almost always lost.
3. •Validation Cycles: In regulated industries like Healthcare or Aerospace, every manual change requires exhaustive re-validation.

Learn more about modernizing legacy UIs

Framework Extraction: Modernizing Embedded UIs with Replay#

The core challenge of framework extraction modernizing embedded systems is the "translation gap." How do you turn a

draw call or a QML into a functional React component with Tailwind CSS?

Replay bridges this gap by treating the legacy UI as a visual data source. Instead of parsing messy C++ code, Replay records the application in motion. It identifies patterns, components, and user flows, then uses its AI Automation Suite to generate clean, documented TypeScript code.

The Technical Workflow#

To modernize an embedded Qt interface, the process follows four distinct phases:

1. •Capture: Record the legacy Qt application as it runs through critical user workflows (e.g., "Calibrate Sensor" or "Emergency Shutdown").
2. •Identify: Replay’s "Blueprints" editor identifies recurring UI patterns—buttons, gauges, charts, and navigation sidebars.
3. •Extract: The platform performs the framework extraction modernizing embedded assets, turning visual elements into a standardized Design System.
4. •Generate: Replay outputs React components that are ready for integration with your new web-based backend.

Video-to-code is the automated pipeline that converts screen recordings of legacy software into functional, high-quality front-end code and design tokens.

Implementation: From Qt Logic to React Components#

Consider a standard Qt "System Status" gauge. In the legacy C++ code, this might be a custom-drawn widget with complex paint events. When modernizing, we want a clean, reusable React component.

Here is what the extracted TypeScript code looks like after Replay processes a legacy embedded screen:

typescript
// Extracted via Replay - Modernized System Gauge
import React from 'react';
import { useSystemMetrics } from '@/hooks/useSystemMetrics';

interface GaugeProps {
  label: string;
  maxValue: number;
  criticalThreshold: number;
}

export const SystemStatusGauge: React.FC<GaugeProps> = ({ 
  label, 
  maxValue, 
  criticalThreshold 
}) => {
  const { currentValue, status } = useSystemMetrics();

  const percentage = (currentValue / maxValue) * 100;
  const isCritical = currentValue >= criticalThreshold;

  return (
    <div className="p-4 border rounded-lg bg-slate-900 text-white">
      <h3 className="text-sm font-medium mb-2">{label}</h3>
      <div className="relative h-4 w-full bg-slate-700 rounded-full overflow-hidden">
        <div 
          className={`h-full transition-all duration-500 ${
            isCritical ? 'bg-red-500' : 'bg-emerald-500'
          }`}
          style={{ width: `${percentage}%` }}
        />
      </div>
      <div className="flex justify-between mt-2 text-xs">
        <span>{currentValue} units</span>
        <span className={isCritical ? 'text-red-400' : 'text-slate-400'}>
          {status}
        </span>
      </div>
    </div>
  );
};

This component isn't just a visual clone; it’s a functional piece of a modern architecture. Replay ensures that the framework extraction modernizing embedded workflows result in code that follows your organization's specific coding standards.

Read about our AI Automation Suite

Managing Complex Workflows with "Flows"#

Embedded systems are rarely just a collection of static screens. They are defined by complex, often safety-critical flows. A single button press might trigger a sequence of hardware checks, state changes, and UI updates.

According to Replay's analysis, the biggest bottleneck in modernization isn't the individual screens—it's the logic between them. Replay’s "Flows" feature maps these transitions visually. By recording a user performing a task in the legacy Qt app, Replay documents the state machine and generates the corresponding React Router or XState logic.

Example: Mapping a Multi-Step Calibration Flow#

In a legacy Qt environment, a calibration flow might be spread across multiple

files and C++ classes. Using Replay, you record the flow once, and it generates a structured representation:

typescript
// Modernized Flow Logic extracted from Legacy Qt Recording
export const CalibrationSequence = {
  id: "sensor-cal-01",
  steps: [
    {
      name: "Initial Check",
      component: "SafetyVerification",
      onNext: "ZeroSensor",
    },
    {
      name: "Zero Sensor",
      component: "ManualAdjustment",
      onNext: "ValidateRange",
    },
    {
      name: "Validation",
      component: "ResultsSummary",
      onFinish: "Dashboard",
    }
  ]
};

This level of framework extraction modernizing embedded systems ensures that business logic is preserved even as the underlying technology stack is completely replaced.

Solving the Documentation Debt#

67% of legacy systems lack documentation. In the embedded world, this usually means the "documentation" is a 500-page PDF from 2008 that no longer matches the actual code.

Replay acts as a living documentation platform. When you perform a framework extraction modernizing embedded UI, Replay doesn't just give you code; it gives you a Library (Design System) and Blueprints (Architectural maps). This becomes the "Single Source of Truth" for both developers and product owners.

Why documentation is the key to modernization

Built for Regulated Industries#

Many Qt applications run in highly regulated environments:

• •Healthcare: Patient monitors and imaging software (HIPAA requirements).
• •Financial Services: Secure kiosks and ATM interfaces (SOC2 requirements).
• •Government/Defense: Control systems (On-premise requirements).

Replay is built for these environments. Unlike generic AI tools that require sending your proprietary code to the cloud, Replay offers On-Premise deployment and is SOC2 and HIPAA-ready. This allows for framework extraction modernizing embedded systems without compromising security or regulatory compliance.

The Replay Advantage: From Months to Weeks#

If you follow the traditional manual path, you are looking at an 18-month average enterprise rewrite timeline. Most of that time is spent in the "Discovery Phase"—trying to figure out what the current system actually does.

Replay collapses the Discovery and Implementation phases into a single automated workflow. By using visual data as the source of truth, you eliminate the need for manual discovery.

1. •Speed: 70% average time savings compared to manual rewrites.
2. •Accuracy: Visual extraction prevents "feature drift" where the new system misses subtle but critical functionality of the old one.
3. •Cost: Reducing the hours per screen from 40 to 4 allows you to reallocate your budget to high-value features rather than just "keeping the lights on."

Framework extraction modernizing embedded software is no longer a manual chore. It is an automated, repeatable process.

Frequently Asked Questions#

How does Replay handle custom Qt widgets that don't have a web equivalent?#

Replay’s AI Automation Suite identifies the visual intent and functional behavior of custom widgets. It then maps them to the closest modern equivalent in your React component library or creates a custom styled-component that replicates the original behavior and look using modern web technologies like HTML5 Canvas or SVG.

Does Replay require access to my legacy C++ source code?#

No. Replay uses Visual Reverse Engineering. It works by "watching" and analyzing the application's UI output and user interactions. This makes it ideal for situations where the original source code is lost, undocumented, or too complex to parse manually.

Can Replay help with the backend migration as well?#

While Replay focuses on UI/UX and front-end architecture, the "Flows" and "Blueprints" it generates provide a clear roadmap for your backend team. By documenting exactly what data the UI needs and when it needs it, Replay simplifies the process of building new APIs to support the modernized interface.

Is the generated React code maintainable?#

Yes. Replay doesn't output "spaghetti code." It generates clean, modular TypeScript components based on your specific Design System and coding standards. The code is structured exactly as if a senior front-end engineer had written it from scratch.

What industries benefit most from Qt framework extraction?#

Any industry relying on long-lifecycle embedded systems—specifically Healthcare, Manufacturing, Automotive, and Defense. These sectors often have robust C++ backends but need to modernize their UIs to support remote monitoring, cloud integration, and better user experiences.

Ready to modernize without rewriting? Book a pilot with Replay