Make QPA think the tabbox is the active window

Summary:
Without pretendingn to activate the Window, Qt will not send
the right signals for accessibility, thus screen readers not working.

Reviewers: kwin, davidedmundson

Reviewed By: davidedmundson

Subscribers: graesslin, davidedmundson

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D16664

CMakeLists.txt

@@ -498,6 +498,7 @@ ecm_qt_declare_logging_category(kwin_KDEINIT_SRCS
 )
 
 if(KWIN_BUILD_TABBOX)
+    include_directories(${Qt5Gui_PRIVATE_INCLUDE_DIRS})
     set(
         kwin_KDEINIT_SRCS ${kwin_KDEINIT_SRCS}
         tabbox/tabbox.cpp

tabbox/tabboxhandler.cpp

@@ -42,6 +42,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QQuickItem>
 #include <QQuickWindow>
 #include <X11/Xlib.h>
+#include <qpa/qwindowsysteminterface.h>
 // KDE
 #include <KLocalizedString>
 #include <KProcess>
@@ -344,6 +345,8 @@ void TabBoxHandlerPrivate::show()
     if (QWindow *w = window()) {
         wheelAngleDelta = 0;
         w->installEventFilter(q);
+        // pretend to activate the window to enable accessibility notifications
+        QWindowSystemInterface::handleWindowActivated(w, Qt::TabFocusReason);
     }
 #endif
 }