xcb: set SM_CLIENT_ID property

SM_CLIENT_ID is required by kwin for proper session management.

- move client leader initialization from screen to connection
- add SM_CLIENT_ID property to client leader

Change-Id: I19fb0d098811c865f6f13d5bc3e59a173c596a65
Task-number: QTBUG-46310
Reviewed-by: Alexander Volkov <a.volkov@rusbitech.ru>
Reviewed-by: Uli Schlachter <psychon@znc.in>
Reviewed-by: Shawn Rutledge <shawn.rutledge@theqtcompany.com>

src/plugins/platforms/xcb/qxcbconnection.cpp

@@ -454,6 +454,7 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGra
     , has_xkb(false)
     , m_buttons(0)
     , m_focusWindow(0)
+    , m_clientLeader(0)
     , m_systemTrayTracker(0)
     , m_glIntegration(Q_NULLPTR)
     , m_xiGrab(false)
@@ -1336,6 +1337,58 @@ xcb_window_t QXcbConnection::rootWindow()
     return s ? s->root() : 0;
 }
 
+xcb_window_t QXcbConnection::clientLeader()
+{
+    if (m_clientLeader == 0) {
+        m_clientLeader = xcb_generate_id(xcb_connection());
+        QXcbScreen *screen = primaryScreen();
+        Q_XCB_CALL(xcb_create_window(xcb_connection(),
+                                     XCB_COPY_FROM_PARENT,
+                                     m_clientLeader,
+                                     screen->root(),
+                                     0, 0, 1, 1,
+                                     0,
+                                     XCB_WINDOW_CLASS_INPUT_OUTPUT,
+                                     screen->screen()->root_visual,
+                                     0, 0));
+#ifndef QT_NO_DEBUG
+        QByteArray ba("Qt client leader window");
+        Q_XCB_CALL(xcb_change_property(xcb_connection(),
+                                       XCB_PROP_MODE_REPLACE,
+                                       m_clientLeader,
+                                       atom(QXcbAtom::_NET_WM_NAME),
+                                       atom(QXcbAtom::UTF8_STRING),
+                                       8,
+                                       ba.length(),
+                                       ba.constData()));
+#endif
+        Q_XCB_CALL(xcb_change_property(xcb_connection(),
+                                       XCB_PROP_MODE_REPLACE,
+                                       m_clientLeader,
+                                       atom(QXcbAtom::WM_CLIENT_LEADER),
+                                       XCB_ATOM_WINDOW,
+                                       32,
+                                       1,
+                                       &m_clientLeader));
+
+#if !defined(QT_NO_SESSIONMANAGER) && defined(XCB_USE_SM)
+        // If we are session managed, inform the window manager about it
+        QByteArray session = qGuiApp->sessionId().toLatin1();
+        if (!session.isEmpty()) {
+            Q_XCB_CALL(xcb_change_property(xcb_connection(),
+                                           XCB_PROP_MODE_REPLACE,
+                                           m_clientLeader,
+                                           atom(QXcbAtom::SM_CLIENT_ID),
+                                           XCB_ATOM_STRING,
+                                           8,
+                                           session.length(),
+                                           session.constData()));
+        }
+#endif
+    }
+    return m_clientLeader;
+}
+
 #ifdef XCB_USE_XLIB
 void *QXcbConnection::xlib_display() const
 {

src/plugins/platforms/xcb/qxcbconnection.h

@@ -403,6 +403,7 @@ public:
 
     QXcbWMSupport *wmSupport() const { return m_wmSupport.data(); }
     xcb_window_t rootWindow();
+    xcb_window_t clientLeader();
 
     bool hasDefaultVisualId() const { return m_defaultVisualId != UINT_MAX; }
     xcb_visualid_t defaultVisualId() const { return m_defaultVisualId; }
@@ -640,6 +641,7 @@ private:
 
     QXcbWindow *m_focusWindow;
 
+    xcb_window_t m_clientLeader;
     QByteArray m_startupId;
     QXcbSystemTrayTracker *m_systemTrayTracker;
     QXcbGlIntegration *m_glIntegration;

src/plugins/platforms/xcb/qxcbscreen.cpp

@@ -170,38 +170,6 @@ QXcbScreen::QXcbScreen(QXcbConnection *connection, QXcbVirtualDesktop *virtualDe
     else
         m_syncRequestSupported = true;
 
-    m_clientLeader = xcb_generate_id(xcb_connection());
-    Q_XCB_CALL2(xcb_create_window(xcb_connection(),
-                                  XCB_COPY_FROM_PARENT,
-                                  m_clientLeader,
-                                  screen()->root,
-                                  0, 0, 1, 1,
-                                  0,
-                                  XCB_WINDOW_CLASS_INPUT_OUTPUT,
-                                  screen()->root_visual,
-                                  0, 0), connection);
-#ifndef QT_NO_DEBUG
-    QByteArray ba("Qt client leader window for screen ");
-    ba += m_outputName.toUtf8();
-    Q_XCB_CALL2(xcb_change_property(xcb_connection(),
-                                   XCB_PROP_MODE_REPLACE,
-                                   m_clientLeader,
-                                   atom(QXcbAtom::_NET_WM_NAME),
-                                   atom(QXcbAtom::UTF8_STRING),
-                                   8,
-                                   ba.length(),
-                                   ba.constData()), connection);
-#endif
-
-    Q_XCB_CALL2(xcb_change_property(xcb_connection(),
-                                    XCB_PROP_MODE_REPLACE,
-                                    m_clientLeader,
-                                    atom(QXcbAtom::WM_CLIENT_LEADER),
-                                    XCB_ATOM_WINDOW,
-                                    32,
-                                    1,
-                                    &m_clientLeader), connection);
-
     xcb_depth_iterator_t depth_iterator =
         xcb_screen_allowed_depths_iterator(screen());
 

src/plugins/platforms/xcb/qxcbscreen.h

@@ -116,8 +116,6 @@ public:
     xcb_randr_crtc_t crtc() const { return m_crtc; }
     xcb_randr_mode_t mode() const { return m_mode; }
 
-    xcb_window_t clientLeader() const { return m_clientLeader; }
-
     void windowShown(QXcbWindow *window);
     QString windowManagerName() const { return m_windowManagerName; }
     bool syncRequestSupported() const { return m_syncRequestSupported; }
@@ -173,7 +171,6 @@ private:
     Qt::ScreenOrientation m_orientation;
     QString m_windowManagerName;
     bool m_syncRequestSupported;
-    xcb_window_t m_clientLeader;
     QMap<xcb_visualid_t, xcb_visualtype_t> m_visuals;
     QMap<xcb_visualid_t, quint8> m_visualDepths;
     QXcbCursor *m_cursor;

src/plugins/platforms/xcb/qxcbwindow.cpp

@@ -622,7 +622,7 @@ void QXcbWindow::create()
 
     xcb_set_wm_hints(xcb_connection(), m_window, &hints);
 
-    xcb_window_t leader = platformScreen->clientLeader();
+    xcb_window_t leader = connection()->clientLeader();
     Q_XCB_CALL(xcb_change_property(xcb_connection(), XCB_PROP_MODE_REPLACE, m_window,
                                    atom(QXcbAtom::WM_CLIENT_LEADER), XCB_ATOM_WINDOW, 32,
                                    1, &leader));
@@ -874,7 +874,7 @@ void QXcbWindow::show()
             // Default to client leader if there is no transient parent, else modal dialogs can
             // be hidden by their parents.
             if (!transientXcbParent)
-                transientXcbParent = xcbScreen()->clientLeader();
+                transientXcbParent = connection()->clientLeader();
             if (transientXcbParent) { // ICCCM 4.1.2.6
                 Q_XCB_CALL(xcb_change_property(xcb_connection(), XCB_PROP_MODE_REPLACE, m_window,
                                                XCB_ATOM_WM_TRANSIENT_FOR, XCB_ATOM_WINDOW, 32,