--- title: MFC/Qt Migration: Bridging OLE IDispatch and QMetaObject description: A technique for migrating legacy MFC/OLE applications to Qt by bridging OLE's IDispatch interface with Qt's QMetaObject system. The QObjectDispatcher class... canonical: https://daily.dev/posts/mfc-qt-migration-bridging-ole-idispatch-and-qmetaobject-souctcv7l twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: MFC/Qt Migration: Bridging OLE IDispatch and QMetaObject | daily.dev og:description: A technique for migrating legacy MFC/OLE applications to Qt by bridging OLE's IDispatch interface with Qt's QMetaObject system. The QObjectDispatcher class... og:url: https://daily.dev/posts/mfc-qt-migration-bridging-ole-idispatch-and-qmetaobject-souctcv7l og:image: https://api.daily.dev/og/posts/SoUcTcv7L.png og:image:alt: MFC/Qt Migration: Bridging OLE IDispatch and QMetaObject og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # MFC/Qt Migration: Bridging OLE IDispatch and QMetaObject **[KDAB Blog](https://daily.dev/sources/kdab)** · 4 min read · 0 upvotes · 0 comments ## Summary A technique for migrating legacy MFC/OLE applications to Qt by bridging OLE's IDispatch interface with Qt's QMetaObject system. The QObjectDispatcher class exposes a QWidget's Q_PROPERTY properties and Q_INVOKABLE methods/slots through IDispatch, letting existing MFC/OLE code that expects a CWnd control continue calling GetIDsOfNames and Invoke as before, unaware the underlying implementation has been ported to Qt. The approach involves wrapping a QWinWidget inside a CWnd, embedding the ported QWidget, and attaching a QObjectDispatcher instance. Limitations include no method overloading, no optional parameters, manual type-mapping for argument types, and the example implementation is not thread-safe. Full example code is available on KDAB's GitHub. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I expose a Qt QWidget through the OLE IDispatch interface when migrating an MFC OCX control to Qt? Create a QObjectDispatcher class that implements IDispatch and maps calls to Qt's Meta Object System. GetIDsOfNames traverses the QMetaObject to find matching methods (declared with Q_INVOKABLE or slots) or properties (declared with Q_PROPERTY), returning method indexes first and property indexes offset by the method count. Invoke then dispatches DISPATCH_METHOD, DISPATCH_PROPERTYGET, or DISPATCH_PROPERTYPUT calls, translating arguments via QMetaMethodArgument or QVariant for properties. _daily.dev surfaces practical writeups like this for teams navigating MFC-to-Qt migrations._ ### What are the limitations of bridging OLE IDispatch with Qt's QMetaObject for legacy MFC migrations? Method overloading is not supported since OLE disallows duplicate names, optional parameters aren't supported because QMetaMethod doesn't reflect them, argument types require manual type-mapping (the example only covers IUnknown*, int, and QString), and the example implementation is not thread-safe. This approach is only recommended for preserving compatibility during a port, not for new code. _developers weighing legacy interop tradeoffs can track practical Qt migration patterns on daily.dev._ ## Similar posts on daily.dev - [QtWidgets to QtQuick, An Application Journey Part 2](https://daily.dev/posts/qtwidgets-to-qtquick-an-application-journey-part-2-etgs3keds) · Qt · 0 upvotes · 0 comments - [Qt Widgets to Qt Quick, An Application Journey Part 3](https://daily.dev/posts/qt-widgets-to-qt-quick-an-application-journey-part-3-vdfmbgxpz) · Qt · 0 upvotes · 0 comments - [Qt Widgets to Qt Quick, An Application Journey Part 4](https://daily.dev/posts/qt-widgets-to-qt-quick-an-application-journey-part-4-5yk8toi9s) · Qt · 0 upvotes · 0 comments --- Tags: [#c++](https://daily.dev/tags/c++), [#qt](https://daily.dev/tags/qt) [View this post on daily.dev](https://daily.dev/posts/mfc-qt-migration-bridging-ole-idispatch-and-qmetaobject-souctcv7l) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"MFC/Qt Migration: Bridging OLE IDispatch and QMetaObject","url":"https://daily.dev/posts/mfc-qt-migration-bridging-ole-idispatch-and-qmetaobject-souctcv7l","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/mfc-qt-migration-bridging-ole-idispatch-and-qmetaobject-souctcv7l"},"datePublished":"2026-08-31T05:54:44.988Z","dateModified":"2026-08-31T05:56:39.521Z","description":"A technique for migrating legacy MFC/OLE applications to Qt by bridging OLE's IDispatch interface with Qt's QMetaObject system. 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