`qmlRegisterType` and related functions not declared - missing `#include <QQmlEngine>`

[astrojuanlu]

I've been trying to build Audacity 4 against KDE's Qt 6.11 and had to include a series of patches to make it work. What follows is an AI-generated report of one of such issues. I see no contributing or AI guidelines so I hope this is acceptable.

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Multiple module registration source files across the muse framework call qmlRegisterType(), qmlRegisterSingletonType(), qmlRegisterUncreatableType(), and qmlRegisterUncreatableMetaObject() without including <QQmlEngine>. These functions are declared in <QQmlEngine> (Qt6) / <QtQml/qqmlengine.h>, but the files only include <qqmlintegration.h>, which does not provide them. The calls compile only when <QQmlEngine> is transitively included through other headers — a dependency that varies between Qt distributions and is being actively removed.

Environment

• muse framework commit: 3c5512eb8ee1a863a6123e62bd75a6ab55045752
• Qt: Built from the KDE Qt fork (the source of the kde-qt6-core24-sdk snap), version 6.11.1

Root cause

In Qt 5, qmlRegisterType() and friends were commonly available through transitive includes from <QtQml>. In Qt 6, the declaration lives in <QQmlEngine> (forwarding to qtqml/qqmlengine.h). The muse framework's module files include <qqmlintegration.h> (for QML_ELEMENT macros) but not <QQmlEngine>. With upstream Qt, <QQmlEngine> is transitively pulled in through other headers; with the KDE Qt fork (which has cleaner transitive include paths), it is not, causing compilation failures.

Affected files

The following files in the muse framework call qmlRegister* functions without including <QQmlEngine>:

• framework/dockwindow/qml/Muse/Dock/dockpanelview.cpp
• framework/rcommand/qml/Muse/RCommand/rcommandmodule.cpp (via generated code)
• framework/extensions/qml/Muse/Extensions/devtools/devextensionslistmodel.cpp
• framework/shortcuts_v2/qml/Muse/Shortcuts/platform/macos/macosshortcutsinstancemodel.mm (macOS only)

Note: Many of the affected files are actually in Audacity's own src/ directory (e.g. src/automation/automationmodule.cpp, src/playback/playbackmodule.cpp, etc.) rather than in the muse framework itself. Those should be reported to the Audacity repository.

Additionally, files that pass QQmlEngine* or QJSEngine* as lambda parameters to qmlRegisterSingletonType need <QQmlEngine> and <QJSEngine>:

• framework/interactive/qml/Muse/Interactive/interactiveprovidermodel.h (uses QQmlEngine in a MOC-registered method)

Suggested fix

Add #include <QQmlEngine> (and #include <QJSEngine> where lambdas use QJSEngine*) to all files that call qmlRegister* functions. Alternatively, consider providing a muse-internal header (e.g. muse_qmlregistration.h) that includes the necessary Qt6 QML headers, so module authors only need to include one muse header.

[astrojuanlu]

This was already partially addressed by #256.