Use target window root instead of kdocker root

Removed some brute code which might have been inserted to
work round the use of the wrong root window.
The 'xdotool' utility operates without such effort.
Added XFlush() as used by 'xdotool' - maybe not necessary?

src/trayitem.cpp

@@ -119,7 +119,9 @@ void TrayItem::restoreWindow() {
     m_is_restoring = true;
 
     Display *display = QX11Info::display();
-    Window root = QX11Info::appRootWindow();
+    XWindowAttributes wattr;
+    XGetWindowAttributes(display, m_window, &wattr);
+    Window root = wattr.screen->root;
 
     if (m_iconified) {
         m_iconified = false;
@@ -130,17 +132,20 @@ void TrayItem::restoreWindow() {
          * window go through Withdrawn->Map->Iconify->Normal state.
          */
         XMapWindow(display, m_window);
+        /*
         XIconifyWindow(display, m_window, DefaultScreen(display));
         XSync(display, False);
         long l_state[1] = {NormalState};
         XLibUtil::sendMessage(display, root, m_window, "WM_CHANGE_STATE", 32, SubstructureNotifyMask | SubstructureRedirectMask, l_state, sizeof (l_state));
+        */
 
         m_sizeHint.flags = USPosition;
         XSetWMNormalHints(display, m_window, &m_sizeHint);
 
         updateToggleAction();
     }
     XMapRaised(display, m_window);
+    XFlush(display);     // DfB - as xdotool
 
     // Change to the desktop that the window was last on.
     long l_currDesk[2] = {m_desktop, CurrentTime};
@@ -182,8 +187,11 @@ void TrayItem::iconifyWindow() {
 
     m_iconified = true;
 
+    /* Get screen number */
     Display *display = QX11Info::display();
-    int screen = DefaultScreen(display);
+    XWindowAttributes attr;
+    XGetWindowAttributes(display, m_window, &attr);
+    int screen = XScreenNumberOfScreen(attr.screen);
     long dummy;
 
     XGetWMNormalHints(display, m_window, &m_sizeHint, &dummy);
@@ -192,7 +200,7 @@ void TrayItem::iconifyWindow() {
      * A simple call to XWithdrawWindow wont do. Here is what we do:
      * 1. Iconify. This will make the application hide all its other windows. For
      *    example, xmms would take off the playlist and equalizer window.
-     * 2. Withdrawn the window so we will be removed from the taskbar.
+     * 2. Withdraw the window to remove it from the taskbar.
      */
     XIconifyWindow(display, m_window, screen); // good for effects too
     XSync(display, False);
@@ -207,9 +215,12 @@ void TrayItem::closeWindow() {
     }
 
     Display *display = QX11Info::display();
+    XWindowAttributes wattr;
+    XGetWindowAttributes(display, m_window, &wattr);
+    Window root = wattr.screen->root;
     long l[5] = {0, 0, 0, 0, 0};
     restoreWindow();
-    XLibUtil::sendMessage(display, QX11Info::appRootWindow(), m_window, "_NET_CLOSE_WINDOW", 32, SubstructureNotifyMask | SubstructureRedirectMask, l, sizeof (l));
+    XLibUtil::sendMessage(display, root, m_window, "_NET_CLOSE_WINDOW", 32, SubstructureNotifyMask | SubstructureRedirectMask, l, sizeof (l));
 }
 
 void TrayItem::doSkipTaskbar() {
@@ -430,10 +441,13 @@ void TrayItem::set_NET_WM_STATE(const char *type, bool set) {
     // set, true = add the state to the window. False, remove the state from
     // the window.
     Display *display = QX11Info::display();
+    XWindowAttributes wattr;
+    XGetWindowAttributes(display, m_window, &wattr);
+    Window root = wattr.screen->root;
     Atom atom = XInternAtom(display, type, False);
 
     qint64 l[2] = {set ? 1 : 0, static_cast<qint64>(atom)};
-    XLibUtil::sendMessage(display, QX11Info::appRootWindow(), m_window, "_NET_WM_STATE", 32, SubstructureNotifyMask, l, sizeof (l));
+    XLibUtil::sendMessage(display, root, m_window, "_NET_WM_STATE", 32, SubstructureNotifyMask, l, sizeof (l));
 }
 
 void TrayItem::readDockedAppName() {