imrove windowChanged signal under X11

--the new code contains more comments and except
blacklisting all NET::Properties2 signals that are
not accompanied with NET::Properties it also
whitelists specific states for NET::WMState.
This should lower a lot the calculations needed
in order to support the dodge visibility modes.
At the same time apps that are abusing X11 signals
should be ignored totally because the whitelisted
states and NET::Properties are only set by the
user or the window manager.

BUG: 399149
FIXED-IN: 0.8.2

app/xwindowinterface.cpp

@@ -348,20 +348,40 @@ void XWindowInterface::windowChangedProxy(WId wid, NET::Properties prop1, NET::P
 
     const auto winType = KWindowInfo(wid, NET::WMWindowType).windowType(NET::DesktopMask);
 
+    //! update desktop id
     if (winType != -1 && (winType & NET::Desktop)) {
         m_desktopId = wid;
         emit windowChanged(wid);
         return;
     }
 
-    //! ignore when, eg: the user presses a key, or a window is sending X events
+    //! accept only NET::Properties events,
+    //! ignore when the user presses a key, or a window is sending X events etc.
     //! without needing to (e.g. Firefox, https://bugzilla.mozilla.org/show_bug.cgi?id=1389953)
-    if (prop1 == 0 && (prop2 == NET::WM2UserTime || prop2 == NET::WM2IconPixmap)) {
+    //! NET::WM2UserTime, NET::WM2IconPixmap etc....
+    if (prop1 == 0) {
         return;
     }
 
-    if (prop1 && !(prop1 & NET::WMState || prop1 & NET::WMGeometry || prop1 & NET::ActiveWindow))
+    //! accepty only the following NET:Properties changed signals
+    //! NET::WMState, NET::WMGeometry, NET::ActiveWindow
+    if (!((prop1 & NET::WMState) || (prop1 & NET::WMGeometry) || (prop1 & NET::ActiveWindow))) {
         return;
+    }
+
+    //! when only WMState changed we can whitelist the acceptable states
+    if ((prop1 & NET::WMState) && !(prop1 & NET::WMGeometry) && !(prop1 & NET::ActiveWindow)) {
+        KWindowInfo info(wid, NET::WMState);
+
+        if (info.valid()) {
+            if (!info.hasState(NET::Sticky) && !info.hasState(NET::Shaded)
+                && !info.hasState(NET::FullScreen) && !info.hasState(NET::Hidden)) {
+                return;
+            }
+        } else {
+            return;
+        }
+    }
 
     emit windowChanged(wid);
 }