qt-bugs@ issue : none yet
Trolltech task ID : none
bugs.kde.org number : none
applied: no
author: Lubos Lunak <l.lunak@kde.org>

 Hello,

 there are several problems with Qt's support for the WM_WINDOW_ROLE property:

- plain "QWidget w; w.setWindowRole( "test" );" aborts with 
Qt::WA_WState_Created not being set

- while QWidgetPrivate::create_sys() uses QObject object name for initial 
setting of WM_WINDOW_ROLE, later calls to QObject::setObjectName() have no 
effect on it

- Qt3 used the QObject object name for setting the window role, however Qt4 
uses some strange mix of object name and what's set manually with 
setWindowRole().

 The result is that that Qt3 and KDE3 apps that had WM_WINDOW_ROLE set don't 
in their Qt4 and KDE4 versions. I suggest using the attached patch which 
fixed all of the above problems:

- set explicit window role is used when actually set, otherwise the object 
name is used. This e.g. takes care of apps ported using setObjectName() from 
their Qt3/KDE3 versions (including e.g. Qt Designer) and generally makes it 
somewhat less demanding to actually set a usable window role (I can't quite 
see how many developers would be bothered to explicitly call 
setWindowRole()).

- calls to QObject::setObjectName() update the WM_WINDOW_ROLE property. Since 
QObjectPrivate already has a virtual dtor I think adding another virtual for 
handling the QWidget-related functionality from QtCore is fine.

--- src/corelib/kernel/qobject.cpp
+++ src/corelib/kernel/qobject.cpp
@@ -1008,9 +1008,18 @@
 {
     Q_D(QObject);
     d->objectName = name;
+#if defined(Q_WS_X11)
+    d->checkWindowRole();
+#endif
 }
 
 
+#if defined(Q_WS_X11)
+void QObjectPrivate::checkWindowRole()
+{
+}
+#endif
+
 #ifdef QT3_SUPPORT
 /*! \internal
     QObject::child is compat but needs to call itself recursively,
--- src/corelib/kernel/qobject_p.h
+++ src/corelib/kernel/qobject_p.h
@@ -139,6 +139,9 @@
     mutable quint32 connectedSignals;
 
     QString objectName;
+#if defined(Q_WS_X11)
+    virtual void checkWindowRole();
+#endif
 };
 
 class QSemaphore;
--- src/gui/kernel/qwidget_p.h
+++ src/gui/kernel/qwidget_p.h
@@ -305,6 +305,7 @@
 
 #if defined(Q_WS_X11)
     void setWindowRole(const char *role);
+    virtual void checkWindowRole();
     void sendStartupMessage(const char *message) const;
 #endif
 
--- src/gui/kernel/qwidget_x11.cpp
+++ src/gui/kernel/qwidget_x11.cpp
@@ -671,11 +671,8 @@
         // when we create a toplevel widget, the frame strut should be dirty
         data.fstrut_dirty = 1;
 
-        // declare the widget's object name as window role
-        QByteArray objName = q->objectName().toLocal8Bit();
-        XChangeProperty(dpy, id,
-                        ATOM(WM_WINDOW_ROLE), XA_STRING, 8, PropModeReplace,
-                        (unsigned char *)objName.constData(), objName.length());
+        // declare the widget's object name as window role if not set
+        setWindowRole( !q->windowRole().isEmpty() ? q->windowRole().toUtf8() : q->objectName().toUtf8());
 
         // set client leader property
         XChangeProperty(dpy, id, ATOM(WM_CLIENT_LEADER),
@@ -2669,12 +2666,20 @@
 void QWidgetPrivate::setWindowRole(const char *role)
 {
     Q_Q(QWidget);
-    Q_ASSERT(q->testAttribute(Qt::WA_WState_Created));
+    if( !q->testAttribute(Qt::WA_WState_Created))
+        return;
     XChangeProperty(X11->display, q->internalWinId(),
                     ATOM(WM_WINDOW_ROLE), XA_STRING, 8, PropModeReplace,
                     (unsigned char *)role, qstrlen(role));
 }
 
+void QWidgetPrivate::checkWindowRole()
+{
+    Q_Q(QWidget);
+    if( q->windowRole().isEmpty())
+        setWindowRole( objectName.toUtf8());
+}
+
 Q_GLOBAL_STATIC(QX11PaintEngine, qt_widget_paintengine)
 QPaintEngine *QWidget::paintEngine() const
 {