qpa: Let platform plugins report old state for window state changes

The previous logic relied on QPlatformWindow::setWindowState() being
synchronous and delivering the QPA event before returning to QWindow,
in which case window->windowState() would still refer to the old
state. Async platforms can now report the previous state correctly.

Change-Id: Ib9148fe23fb62be55b7e3a0ccf63d32c71dc2ad3
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

4 files changed, 11 insertions, 6 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index e4eabc815e..7c596d5ae5 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -2162,7 +2162,7 @@ void QGuiApplicationPrivate::processActivatedEvent(QWindowSystemInterfacePrivate
 void QGuiApplicationPrivate::processWindowStateChangedEvent(QWindowSystemInterfacePrivate::WindowStateChangedEvent *wse)
 {
     if (QWindow *window  = wse->window.data()) {
-        QWindowStateChangeEvent e(window->windowState());
+        QWindowStateChangeEvent e(wse->oldState);
         window->d_func()->windowState = wse->newState;
         QGuiApplication::sendSpontaneousEvent(window, &e);
     }
diff --git a/src/gui/kernel/qwindowsysteminterface.cpp b/src/gui/kernel/qwindowsysteminterface.cpp
index 2fc713f708..7ad4f57198 100644
--- a/src/gui/kernel/qwindowsysteminterface.cpp
+++ b/src/gui/kernel/qwindowsysteminterface.cpp
@@ -241,10 +241,14 @@ QT_DEFINE_QPA_EVENT_HANDLER(void, handleWindowActivated, QWindow *window, Qt::Fo
     QWindowSystemInterfacePrivate::handleWindowSystemEvent<Delivery>(e);
 }
 
-QT_DEFINE_QPA_EVENT_HANDLER(void, handleWindowStateChanged, QWindow *window, Qt::WindowState newState)
+QT_DEFINE_QPA_EVENT_HANDLER(void, handleWindowStateChanged, QWindow *window, Qt::WindowState newState, int oldState)
 {
+    Q_ASSERT(window);
+    if (oldState < Qt::WindowNoState)
+        oldState = window->windowState();
+
     QWindowSystemInterfacePrivate::WindowStateChangedEvent *e =
-        new QWindowSystemInterfacePrivate::WindowStateChangedEvent(window, newState);
+        new QWindowSystemInterfacePrivate::WindowStateChangedEvent(window, newState, Qt::WindowState(oldState));
     QWindowSystemInterfacePrivate::handleWindowSystemEvent<Delivery>(e);
 }
 
diff --git a/src/gui/kernel/qwindowsysteminterface.h b/src/gui/kernel/qwindowsysteminterface.h
index eb52dd89b6..253584314c 100644
--- a/src/gui/kernel/qwindowsysteminterface.h
+++ b/src/gui/kernel/qwindowsysteminterface.h
@@ -176,7 +176,7 @@ public:
     static void handleWindowActivated(QWindow *window, Qt::FocusReason r = Qt::OtherFocusReason);
 
     template<typename Delivery = QWindowSystemInterface::DefaultDelivery>
-    static void handleWindowStateChanged(QWindow *window, Qt::WindowState newState);
+    static void handleWindowStateChanged(QWindow *window, Qt::WindowState newState, int oldState = -1);
     static void handleWindowScreenChanged(QWindow *window, QScreen *newScreen);
 
     static void handleApplicationStateChanged(Qt::ApplicationState newState, bool forcePropagate = false);
diff --git a/src/gui/kernel/qwindowsysteminterface_p.h b/src/gui/kernel/qwindowsysteminterface_p.h
index 1db60e8cb8..1bcc79552d 100644
--- a/src/gui/kernel/qwindowsysteminterface_p.h
+++ b/src/gui/kernel/qwindowsysteminterface_p.h
@@ -168,12 +168,13 @@ public:
 
     class WindowStateChangedEvent : public WindowSystemEvent {
     public:
-        WindowStateChangedEvent(QWindow *_window, Qt::WindowState _newState)
-            : WindowSystemEvent(WindowStateChanged), window(_window), newState(_newState)
+        WindowStateChangedEvent(QWindow *_window, Qt::WindowState _newState, Qt::WindowState _oldState)
+            : WindowSystemEvent(WindowStateChanged), window(_window), newState(_newState), oldState(_oldState)
         { }
 
         QPointer<QWindow> window;
         Qt::WindowState newState;
+        Qt::WindowState oldState;
     };
 
     class WindowScreenChangedEvent : public WindowSystemEvent {