Vendored KDDockWidgets: `DockWidgetBase.cpp` missing `#include <QAction>`

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.

The muse framework vendors KDDockWidgets 1.4.95 (circa 2021). This version's DockWidgetBase.cpp uses QAction methods without including <QAction>, relying on transitive includes that vary between Qt distributions. The code compiles only when <QAction> happens to be transitively included through other QtGui headers — a dependency that is not guaranteed across Qt distributions and is being actively removed.

Environment

• muse framework commit: 3c5512eb8ee1a863a6123e62bd75a6ab55045752
• Vendored KDDockWidgets version: 1.4.95 (in muse/framework/dockwindow/thirdparty/KDDockWidgets/)
• Qt: Built from the KDE Qt fork (the source of the kde-qt6-core24-sdk snap), version 6.11.1

Error

DockWidgetBase.cpp:611:20: error: invalid use of incomplete type 'class QAction'
DockWidgetBase.cpp:612:20: error: invalid use of incomplete type 'class QAction'

The forward declaration comes from QtGui/qevent.h (which forward-declares QAction), but the full definition in <QAction> is never included.

Root cause

DockWidgetBase.cpp includes <QTimer> but not <QAction>. It calls methods on QAction objects via pointers (e.g. floatAction->setEnabled(true)), which requires the complete type. With upstream Qt, <QAction> is transitively included; with the KDE Qt fork (which has cleaner transitive include paths), it is not.

Suggested fix

Add #include <QAction> to the vendored DockWidgetBase.cpp:

 #include <QTimer>
+#include <QAction>
 #include <QScopedValueRollback>

Note on upstream

This issue is already fixed in upstream KDDockWidgets 2.x (github.com/KDAB/KDDockWidgets), which completely restructured the codebase and no longer has DockWidgetBase.cpp. However, upgrading the vendored snapshot from 1.4.95 to 2.x could be a disruptive change for the muse framework. The one-line #include patch above is the minimal fix for the vendored 1.4.95 snapshot.

Open muse/framework/dockwindow/thirdparty/KDDockWidgets/DockWidgetBase.cpp and inspect the include block around . Add the missing QAction include, then build Audacity 4 or the muse framework against Qt 6.11; done means the incomplete QAction errors at the reported lines no longer occur.