With the suggested patch applied, the build fails with:

AutoMoc subprocess error
------------------------
The moc process failed to compile
"SRC:/src/VRMirror.cpp"
into
"SRC:/obj-x86_64-linux-gnu/src/kwin_effect_xrdesktop_autogen/include/VRMirror.moc"
included by
"SRC:/src/VRMirror.cpp"
Process failed with return value 1

Command
-------
/usr/lib/qt5/bin/moc -DKCOREADDONS_LIB -DQT_CORE_LIB -DQT_DBUS_LIB -DQT_GUI_LIB -DQT_NO_DEBUG -DQT_WIDGETS_LIB
-Dkwin_effect_xrdesktop_EXPORTS -I/home/bage/kwin-effect-xrdesktop/obj-x86_64-linux-gnu/src
-I/home/bage/kwin-effect-xrdesktop/src -I/usr/include/xrdesktop-0.15 -I/usr/include/gxr-0.15 -I/usr/include/gulkan-0.15
-I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/include/cairo -I/usr/include/libpng16
-I/usr/include/freetype2 -I/usr/include/pixman-1 -I/usr/include/graphene-1.0 -I/usr/lib/x86_64-linux-gnu/graphene-1.0/include -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/webp
-I/usr/include/libmount -I/usr/include/blkid -I/usr/include/gtk-3.0 -I/usr/include/pango-1.0 -I/usr/include/harfbuzz
-I/usr/include/fribidi -I/usr/include/gio-unix-2.0 -I/usr/include/cloudproviders -I/usr/include/libinputsynth-0.15
-I/usr/include/x86_64-linux-gnu/qt5 -I/usr/include/x86_64-linux-gnu/qt5/QtCore -I/usr/lib/x86_64-linux-gnu/qt5/mkspecs/linux-g++ -I/usr/include/KF5/KWindowSystem -I/usr/include/KF5
-I/usr/include/x86_64-linux-gnu/qt5/QtGui -I/usr/include/x86_64-linux-gnu/qt5/QtWidgets -I/usr/include/KF5/KService
-I/usr/include/KF5/KConfig -I/usr/include/KF5/KConfigCore -I/usr/include/KF5/KCoreAddons -I/usr/include/KF5/KGlobalAccel
-I/usr/include/x86_64-linux-gnu/qt5/QtDBus -I/usr/include/KF5/KI18n -I/usr/include -I/usr/include/x86_64-linux-gnu
-I/usr/include/c++/13 -I/usr/include/x86_64-linux-gnu/c++/13 -I/usr/include/c++/13/backward
-I/usr/lib/gcc/x86_64-linux-gnu/13/include -I/usr/local/include --include /home/bage/kwin-effect-xrdesktop/obj-x86_64-linux-gnu/src/kwin_effect_xrdesktop_autogen/moc_predefs.h -nw
--output-dep-file -o /home/bage/kwin-effect-xrdesktop/obj-x86_64-linux-gnu/src/kwin_effect_xrdesktop_autogen/include/VRMirror.moc
/home/bage/kwin-effect-xrdesktop/src/VRMirror.cpp

Output
------
/home/bage/kwin-effect-xrdesktop/src/VRMirror.cpp:182: Parse error at "FILE"

AutoMoc: Reading dependencies from "SRC:/obj-x86_64-linux-gnu/src/kwin_effect_xrdesktop_autogen/EWIEGA46WW/moc_VRMirror.cpp.d"
make[3]: *** [src/CMakeFiles/kwin_effect_xrdesktop_autogen.dir/build.make:77: src/kwin_effect_xrdesktop_autogen/timestamp] Error 1
make[3]: Leaving directory '/home/bage/kwin-effect-xrdesktop/obj-x86_64-linux-gnu'
make[2]: *** [CMakeFiles/Makefile2:266: src/CMakeFiles/kwin_effect_xrdesktop_autogen.dir/all] Error 2

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)