2 files changed, 46 insertions, 11 deletions

diff --git a/src/plugins/platforms/windows/qwindowsmousehandler.cpp b/src/plugins/platforms/windows/qwindowsmousehandler.cpp
index 55cf3a3a53..2d60c87438 100644
--- a/src/plugins/platforms/windows/qwindowsmousehandler.cpp
+++ b/src/plugins/platforms/windows/qwindowsmousehandler.cpp
@@ -269,6 +269,17 @@ bool QWindowsMouseHandler::translateMouseEvent(QWindow *window, HWND hwnd,
     return true;
 }
 
+static bool isValidWheelReceiver(QWindow *candidate)
+{
+    if (candidate) {
+        const QWindow *toplevel = QWindowsWindow::topLevelOf(candidate);
+        if (const QWindowsWindow *ww = QWindowsWindow::baseWindowOf(toplevel))
+            return !ww->testFlag(QWindowsWindow::BlockedByModal);
+    }
+
+    return false;
+}
+
 bool QWindowsMouseHandler::translateMouseWheelEvent(QWindow *window, HWND,
                                                     MSG msg, LRESULT *)
 {
@@ -292,18 +303,26 @@ bool QWindowsMouseHandler::translateMouseWheelEvent(QWindow *window, HWND,
     if (msg.message == WM_MOUSEHWHEEL)
         delta = -delta;
 
+    // Redirect wheel event to one of the following, in order of preference:
+    // 1) The window under mouse
+    // 2) The window receiving the event
+    // If a window is blocked by modality, it can't get the event.
     const QPoint globalPos(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
-    // TODO: if there is a widget under the mouse and it is not shadowed
-    // QWindow *receiver = windowAt(pos);
-    // by modality, we send the event to it first.
-    //synaptics touchpad shows its own widget at this position
-    //so widgetAt() will fail with that HWND, try child of this widget
-    // if (!receiver) receiver = window->childAt(pos);
-    QWindow *receiver = window;
-    QWindowSystemInterface::handleWheelEvent(receiver,
-                                             QWindowsGeometryHint::mapFromGlobal(receiver, globalPos),
-                                             globalPos,
-                                             delta, orientation, mods);
+    QWindow *receiver = QWindowsScreen::windowAt(globalPos);
+    bool handleEvent = true;
+    if (!isValidWheelReceiver(receiver)) {
+        receiver = window;
+        if (!isValidWheelReceiver(receiver))
+            handleEvent = false;
+    }
+
+    if (handleEvent) {
+        QWindowSystemInterface::handleWheelEvent(receiver,
+                                                 QWindowsGeometryHint::mapFromGlobal(receiver, globalPos),
+                                                 globalPos,
+                                                 delta, orientation, mods);
+    }
+
     return true;
 }
 
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 2f7058ab97..955617e399 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -783,10 +783,26 @@ void QWindowsWindow::unregisterDropSite()
     }
 }
 
+// Returns topmost QWindowsWindow ancestor even if there are embedded windows in the chain.
+// Returns this window if it is the topmost ancestor.
 QWindow *QWindowsWindow::topLevelOf(QWindow *w)
 {
     while (QWindow *parent = w->parent())
         w = parent;
+
+    const QWindowsWindow *ww = static_cast<const QWindowsWindow *>(w->handle());
+
+    // In case the topmost parent is embedded, find next ancestor using native methods
+    if (ww->isEmbedded(0)) {
+        HWND parentHWND = GetAncestor(ww->handle(), GA_PARENT);
+        const HWND desktopHwnd = GetDesktopWindow();
+        const QWindowsContext *ctx = QWindowsContext::instance();
+        while (parentHWND && parentHWND != desktopHwnd) {
+            if (QWindowsWindow *ancestor = ctx->findPlatformWindow(parentHWND))
+                return topLevelOf(ancestor->window());
+            parentHWND = GetAncestor(parentHWND, GA_PARENT);
+        }
+    }
     return w;
 }