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Qt 6.12 was announced on 30 September 2026 as a Long-Term Support release. Its headline changes for Qt and QML developers are built-in QML hot reload and Qt Canvas Painter, an imperative 2D drawing API designed to render through Qt’s Rendering Hardware Interface (QRhi). The key distinction: Qt says the core Canvas Painter module is maintained and ready for production use, while its new QtCanvas2D QML API remains in Technology Preview.
What’s new in Qt 6.12 LTS?
Qt’s release announcement highlights two changes aimed at application developers: a live-preview workflow for QML and a new GPU-oriented route for imperative 2D drawing. The release also adds official HarmonyOS support as an LTS platform, according to Qt. The versioned Qt 6.12 change log documents additional module and API changes.
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Qt describes Qt 6.12 as an LTS release maintained over a five-year period. That is Qt’s stated maintenance horizon; it does not, by itself, establish the support terms, licensing status, or regulatory compliance of a particular project. See the Qt 6.12 release announcement for the vendor’s release details.
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Qt says the QML Engine now has native hot reload support, allowing developers to preview a running QML interface as they edit its code. Qt names Qt Creator and the qmlpreview command-line tool as ways to access live preview; the release announcement says qmlpreview was reworked to use the engine support.
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This describes a live-preview capability, not a promise that every edit can be applied without restarting, that application state is always preserved, or that reload latency is a particular amount. Qt has not provided a quantified performance result for the feature in the cited release materials. Details are in Qt’s hot reload release description.
Is Qt Canvas Painter production-ready, or still a technology preview?
Both descriptions apply to different parts of the feature. Qt says the core Qt Canvas Painter module has moved out of Technology Preview and is maintained. The separate QtCanvas2D QML API, which is backed by Canvas Painter, remains in Technology Preview. Treat their maturity separately when deciding whether to adopt the API.
Core Qt Canvas Painter
Canvas Painter is an imperative, painter-like 2D rendering API for C++ and QML. Qt designed it around QRhi, its Rendering Hardware Interface, to use GPU rendering; shaders can also be used for visual effects. Qt describes the API as generally following HTML Canvas 2D conventions, with differences. Its documentation covers the Qt 6.12 module status and changes.
QtCanvas2D for QML
QtCanvas2D provides a QML element through which JavaScript can draw shapes that Canvas Painter renders via QRhi. Qt presents it as a modern architectural replacement for Qt Quick Canvas, but explicitly retains the new API in Technology Preview. If a project requires a supported, production-ready API, do not treat the preview status of QtCanvas2D as equivalent to the maturity of the core module.
What changed for graphs and drawing paths?
Qt 6.12 makes Canvas Painter available as an optional rendering backend for 2D graphs. It is enabled at configure time with -feature-graphs-2d-high-performance-backend; it is not described as the default backend. Qt says it wants feedback before making the backend the default. This option may be worth evaluating for graph-heavy applications, but Qt’s cited materials do not provide an independent benchmark or a quantified speedup.
The Qt 6.12 change log also lists support for SVG path strings in QCanvasPath::addPath() and new fill-rule support. Consult the versioned change log for the precise API changes and configuration context.
What should teams check before adopting Qt 6.12?
- Maintenance and licensing: Qt states a five-year maintenance period for this LTS release. Check the support and licensing terms that apply to your own project rather than inferring them from the LTS label.
- API maturity: Distinguish the maintained core Canvas Painter module from the Technology Preview QtCanvas2D QML API.
- Target platforms: Validate that your deployment targets and platform requirements match your application; Qt’s announcement specifically highlights official HarmonyOS support.
- Migration and validation: Assess the upgrade against your existing Qt version, dependencies, and test coverage. The cited release materials do not establish migration effort for a particular application.
- Actual workflow needs: Evaluate whether live QML preview or imperative GPU-oriented drawing solves a current project problem. Qt’s release material does not quantify productivity gains or performance for a project’s workload.
What Qt says about CRA compliance
Qt says its commercial Qt 6.12 release is compliant with the EU Cyber Resilience Act (CRA), and also says that this does not automatically make a customer’s finished product compliant. Customers still have their own CRA work to do. This is Qt’s statement about its commercial release, not legal advice or a blanket compliance assurance for products built with Qt. See the release announcement for Qt’s qualification.
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