Save the last known window state from the window manager POV

Required for QTBUG-102430

src/private/FloatingWindow.cpp

@@ -654,6 +654,11 @@ QRect FloatingWindow::normalGeometry() const
     return QWidgetAdapter::normalGeometry();
 }
 
+Qt::WindowState FloatingWindow::lastWindowManagerState() const
+{
+    return m_lastWindowManagerState;
+}
+
 int FloatingWindow::userType() const
 {
     if (Frame *f = singleFrame())

src/private/FloatingWindow_p.h

@@ -212,6 +212,11 @@ public:
     /// @sa QTBUG-95478
     virtual QRect normalGeometry() const;
 
+    // The state reported by QWidget is not always the same as what the
+    // window manager thinks, due to the async nature. This method
+    // returns the last state reported by the window manager itself.
+    Qt::WindowState lastWindowManagerState() const;
+
     ///@brief Allows the user app to specify which window flags to use, instead of KDDWs default ones
     ///Bugs caused by this won't be supported, as the amount of combinations that could go wrong can
     ///be open ended
@@ -234,6 +239,7 @@ protected:
 
     QPointer<DropArea> m_dropArea;
     TitleBar *const m_titleBar;
+    Qt::WindowState m_lastWindowManagerState = Qt::WindowNoState;
 
 private:
     Q_DISABLE_COPY(FloatingWindow)

src/private/widgets/FloatingWindowWidget.cpp

@@ -96,8 +96,10 @@ bool FloatingWindowWidget::eventFilter(QObject *, QEvent *ev)
         // The sync one being useless, as the window manager can still have the old state.
         // Only emit windowStateChanged once the window manager tells us the state has actually changed
         // See also QTBUG-102430
-        if (ev->spontaneous())
+        if (ev->spontaneous()) {
+            m_lastWindowManagerState = windowHandle()->windowState();
             Q_EMIT windowStateChanged();
+        }
     }
 
     return false;