Fix wheel events in Windows

Wheel events were always passed to window that got them from native
message loop, which isn't what Qt expects. Changed the receiver to
preferably be the window under cursor, as long as it is not blocked by
modal window.

Change-Id: I4edf0608842fe5b822a7f574abfdae81fa755ee5
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

1 files changed, 30 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;
 }