Windows QPA: Fix mouse button reported in non-client events

The current mouse buttons state was being retrieved from WPARAM
for all mouse messages. However, for non-client messages this
parameter contains unrelated information, which resulted in
non-client events reporting incorrect button state. Changing it to
retrieve state using GetAsyncKeyState() for non-client messages,
like in the legacy mouse handler implementation.

Fixes: QTBUG-74649
Change-Id: Ia246164208707072e584dd521697e9d31d3e65ad
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 21 insertions, 2 deletions

diff --git a/src/plugins/platforms/windows/qwindowspointerhandler.cpp b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
index f1960f1585..2673c04c48 100644
--- a/src/plugins/platforms/windows/qwindowspointerhandler.cpp
+++ b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
@@ -250,6 +250,23 @@ static Qt::MouseButtons mouseButtonsFromKeyState(WPARAM keyState)
     return result;
 }
 
+static Qt::MouseButtons queryMouseButtons()
+{
+    Qt::MouseButtons result = Qt::NoButton;
+    const bool mouseSwapped = GetSystemMetrics(SM_SWAPBUTTON);
+    if (GetAsyncKeyState(VK_LBUTTON) < 0)
+        result |= mouseSwapped ? Qt::RightButton: Qt::LeftButton;
+    if (GetAsyncKeyState(VK_RBUTTON) < 0)
+        result |= mouseSwapped ? Qt::LeftButton : Qt::RightButton;
+    if (GetAsyncKeyState(VK_MBUTTON) < 0)
+        result |= Qt::MidButton;
+    if (GetAsyncKeyState(VK_XBUTTON1) < 0)
+        result |= Qt::XButton1;
+    if (GetAsyncKeyState(VK_XBUTTON2) < 0)
+        result |= Qt::XButton2;
+    return result;
+}
+
 static QWindow *getWindowUnderPointer(QWindow *window, QPoint globalPos)
 {
     QWindow *currentWindowUnderPointer = QWindowsScreen::windowAt(globalPos, CWP_SKIPINVISIBLE | CWP_SKIPTRANSPARENT);
@@ -681,7 +698,6 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window,
     }
 
     const Qt::KeyboardModifiers keyModifiers = QWindowsKeyMapper::queryKeyboardModifiers();
-    const Qt::MouseButtons mouseButtons = mouseButtonsFromKeyState(msg.wParam);
     QWindow *currentWindowUnderPointer = getWindowUnderPointer(window, globalPos);
 
     if (et == QtWindows::MouseWheelEvent)
@@ -709,7 +725,8 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window,
     const MouseEvent mouseEvent = eventFromMsg(msg);
 
     if (mouseEvent.type >= QEvent::NonClientAreaMouseMove && mouseEvent.type <= QEvent::NonClientAreaMouseButtonDblClick) {
-        QWindowSystemInterface::handleFrameStrutMouseEvent(window, localPos, globalPos, mouseButtons,
+        const Qt::MouseButtons nonclientButtons = queryMouseButtons();
+        QWindowSystemInterface::handleFrameStrutMouseEvent(window, localPos, globalPos, nonclientButtons,
                                                            mouseEvent.button, mouseEvent.type, keyModifiers, source);
         return false; // Allow further event processing
     }
@@ -725,6 +742,8 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window,
         return true;
     }
 
+    const Qt::MouseButtons mouseButtons = mouseButtonsFromKeyState(msg.wParam);
+
     handleCaptureRelease(window, currentWindowUnderPointer, hwnd, mouseEvent.type, mouseButtons);
     handleEnterLeave(window, currentWindowUnderPointer, globalPos);