3 files changed, 18 insertions, 8 deletions
diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index 5b8cc7893a..90aa3fef16 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -302,7 +302,12 @@ QPlatformWindow *QWindowsIntegration::createPlatformWindow(QWindow *window) cons
     }
 
     if (window->type() == Qt::ForeignWindow) {
-        QWindowsForeignWindow *result = new QWindowsForeignWindow(window, reinterpret_cast<HWND>(window->winId()));
+        const HWND hwnd = reinterpret_cast<HWND>(window->winId());
+        if (!IsWindow(hwnd)) {
+           qWarning("Windows QPA: Invalid foreign window ID %p.");
+           return nullptr;
+        }
+        QWindowsForeignWindow *result = new QWindowsForeignWindow(window, hwnd);
         const QRect obtainedGeometry = result->geometry();
         QScreen *screen = Q_NULLPTR;
         if (const QPlatformScreen *pScreen = result->screenForGeometry(obtainedGeometry))
diff --git a/src/plugins/platforms/windows/qwindowstheme.cpp b/src/plugins/platforms/windows/qwindowstheme.cpp
index e84033f5e4..2c3ffd45d9 100644
--- a/src/plugins/platforms/windows/qwindowstheme.cpp
+++ b/src/plugins/platforms/windows/qwindowstheme.cpp
@@ -389,8 +389,13 @@ QVariant QWindowsTheme::themeHint(ThemeHint hint) const
         return QVariant(booleanSystemParametersInfo(SPI_GETSNAPTODEFBUTTON, false));
     case ContextMenuOnMouseRelease:
         return QVariant(true);
-    case WheelScrollLines:
-        return QVariant(int(dWordSystemParametersInfo(SPI_GETWHEELSCROLLLINES, 3)));
+    case WheelScrollLines: {
+        int result = 3;
+        const DWORD scrollLines = dWordSystemParametersInfo(SPI_GETWHEELSCROLLLINES, DWORD(result));
+        if (scrollLines != DWORD(-1)) // Special value meaning "scroll one screen", unimplemented in Qt.
+            result = int(scrollLines);
+        return QVariant(result);
+    }
     default:
         break;
     }
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 29f0af4621..7289f8de6d 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -1504,7 +1504,7 @@ void QWindowsWindow::handleGeometryChange()
             QWindowSystemInterface::handleWindowScreenChanged(window(), newScreen->screen());
     }
     if (testFlag(SynchronousGeometryChangeEvent))
-        QWindowSystemInterface::flushWindowSystemEvents();
+        QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents);
 
     qCDebug(lcQpaEvents) << __FUNCTION__ << this << window() << m_data.geometry;
 }
@@ -1596,7 +1596,7 @@ bool QWindowsWindow::handleWmPaint(HWND hwnd, UINT message,
     // Our tests depend on it.
     fireExpose(QRegion(qrectFromRECT(ps.rcPaint)), true);
     if (!QWindowsContext::instance()->asyncExpose())
-        QWindowSystemInterface::flushWindowSystemEvents();
+        QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents);
 
     EndPaint(hwnd, &ps);
     return true;
@@ -1656,7 +1656,7 @@ void QWindowsWindow::handleWindowStateChange(Qt::WindowState state)
     switch (state) {
     case Qt::WindowMinimized:
         handleHidden();
-        QWindowSystemInterface::flushWindowSystemEvents(); // Tell QQuickWindow to stop rendering now.
+        QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents); // Tell QQuickWindow to stop rendering now.
         break;
     case Qt::WindowMaximized:
     case Qt::WindowFullScreen:
@@ -1679,7 +1679,7 @@ void QWindowsWindow::handleWindowStateChange(Qt::WindowState state)
             }
         }
         if (exposeEventsSent && !QWindowsContext::instance()->asyncExpose())
-            QWindowSystemInterface::flushWindowSystemEvents();
+            QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents);
     }
         break;
     default:
@@ -1769,7 +1769,7 @@ void QWindowsWindow::setWindowState_sys(Qt::WindowState newState)
             if (!wasSync)
                 clearFlag(SynchronousGeometryChangeEvent);
             QWindowSystemInterface::handleGeometryChange(window(), r);
-            QWindowSystemInterface::flushWindowSystemEvents();
+            QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents);
         } else if (newState != Qt::WindowMinimized) {
             // Restore saved state.
             unsigned newStyle = m_savedStyle ? m_savedStyle : style();