emit QWindow::windowStateChanged only when state has changed

Upon programmatic window state changes, windowStateChange was fired
once in QWindow::setWindowStates and once when the visual state had
been changed by the window interface.

This patch adds if guards to ensure that the singal is fired only once.

It adds a corresponding autotest to tst_QWindow.
tst_QWidget::resizePropagation() is adapted to no longer expect double
signal emission.

Fixes: QTBUG-102478
Pick-to: 6.4 6.2
Change-Id: If093c0a883d76d8a676e4fab90db6b0676452267
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

2 files changed, 14 insertions, 4 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 36030cac42..c721cfd802 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -2509,11 +2509,16 @@ void QGuiApplicationPrivate::processWindowStateChangedEvent(QWindowSystemInterfa
 {
     if (QWindow *window = wse->window.data()) {
         QWindowPrivate *windowPrivate = qt_window_private(window);
-        const auto newEffectiveState = QWindowPrivate::effectiveState(windowPrivate->windowState);
-        QWindowStateChangeEvent e(wse->oldState);
+        const auto originalEffectiveState = QWindowPrivate::effectiveState(windowPrivate->windowState);
+
         windowPrivate->windowState = wse->newState;
-        emit window->windowStateChanged(newEffectiveState);
+        const auto newEffectiveState = QWindowPrivate::effectiveState(windowPrivate->windowState);
+        if (newEffectiveState != originalEffectiveState)
+            emit window->windowStateChanged(newEffectiveState);
+
         windowPrivate->updateVisibility();
+
+        QWindowStateChangeEvent e(wse->oldState);
         QGuiApplication::sendSpontaneousEvent(window, &e);
     }
 }
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index d01ff11aa7..13e2051e14 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -1384,8 +1384,13 @@ void QWindow::setWindowStates(Qt::WindowStates state)
 
     if (d->platformWindow)
         d->platformWindow->setWindowState(state);
+
+    auto originalEffectiveState = QWindowPrivate::effectiveState(d->windowState);
     d->windowState = state;
-    emit windowStateChanged(QWindowPrivate::effectiveState(d->windowState));
+    auto newEffectiveState = QWindowPrivate::effectiveState(d->windowState);
+    if (newEffectiveState != originalEffectiveState)
+        emit windowStateChanged(newEffectiveState);
+
     d->updateVisibility();
 }