Windows QPA: Fix incorrect button state reporting for touchpad

The current state of (emulated) mouse buttons was being incorrectly
reported for touchpad events under some conditions. In the handling
of pointer messages, GetAsyncKeyState() was being used to retrieve the
mouse button state. However, it does not seem to work always with all
touchpads. Furthermore, its use is not necessary, since the button
state information comes as a set of flags with the pointer message
itself. This change makes the handler use these flags instead.

Fixes: QTBUG-71470
Change-Id: Ie2e35bd80778ef74db672604a0f2af659785efbf
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 34 insertions, 20 deletions

diff --git a/src/plugins/platforms/windows/qwindowspointerhandler.cpp b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
index 2b6c696979..4d3e2f71ec 100644
--- a/src/plugins/platforms/windows/qwindowspointerhandler.cpp
+++ b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
@@ -336,6 +336,38 @@ static void getMouseEventInfo(UINT message, POINTER_BUTTON_CHANGE_TYPE changeTyp
     *mouseButton = buttonMapping.value(changeType, Qt::NoButton);
 }
 
+static Qt::MouseButtons mouseButtonsFromPointerFlags(POINTER_FLAGS pointerFlags)
+{
+    Qt::MouseButtons result = Qt::NoButton;
+    if (pointerFlags & POINTER_FLAG_FIRSTBUTTON)
+        result |= Qt::LeftButton;
+    if (pointerFlags & POINTER_FLAG_SECONDBUTTON)
+        result |= Qt::RightButton;
+    if (pointerFlags & POINTER_FLAG_THIRDBUTTON)
+        result |= Qt::MiddleButton;
+    if (pointerFlags & POINTER_FLAG_FOURTHBUTTON)
+        result |= Qt::XButton1;
+    if (pointerFlags & POINTER_FLAG_FIFTHBUTTON)
+        result |= Qt::XButton2;
+    return result;
+}
+
+static Qt::MouseButtons mouseButtonsFromKeyState(WPARAM keyState)
+{
+    Qt::MouseButtons result = Qt::NoButton;
+    if (keyState & MK_LBUTTON)
+        result |= Qt::LeftButton;
+    if (keyState & MK_RBUTTON)
+        result |= Qt::RightButton;
+    if (keyState & MK_MBUTTON)
+        result |= Qt::MiddleButton;
+    if (keyState & MK_XBUTTON1)
+        result |= Qt::XButton1;
+    if (keyState & MK_XBUTTON2)
+        result |= Qt::XButton2;
+    return result;
+}
+
 static QWindow *getWindowUnderPointer(QWindow *window, QPoint globalPos)
 {
     QWindow *currentWindowUnderPointer = QWindowsScreen::windowAt(globalPos, CWP_SKIPINVISIBLE | CWP_SKIPTRANSPARENT);
@@ -405,23 +437,6 @@ QTouchDevice *QWindowsPointerHandler::ensureTouchDevice()
     return m_touchDevice;
 }
 
-Qt::MouseButtons QWindowsPointerHandler::queryMouseButtons()
-{
-    Qt::MouseButtons result = 0;
-    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;
-}
-
 bool QWindowsPointerHandler::translateMouseTouchPadEvent(QWindow *window, HWND hwnd,
                                                          QtWindows::WindowsEventType et,
                                                          MSG msg, PVOID vPointerInfo)
@@ -430,7 +445,7 @@ bool QWindowsPointerHandler::translateMouseTouchPadEvent(QWindow *window, HWND h
     const QPoint globalPos = QPoint(pointerInfo->ptPixelLocation.x, pointerInfo->ptPixelLocation.y);
     const QPoint localPos = QWindowsGeometryHint::mapFromGlobal(hwnd, globalPos);
     const Qt::KeyboardModifiers keyModifiers = QWindowsKeyMapper::queryKeyboardModifiers();
-    const Qt::MouseButtons mouseButtons = queryMouseButtons();
+    const Qt::MouseButtons mouseButtons = mouseButtonsFromPointerFlags(pointerInfo->pointerFlags);
 
     QWindow *currentWindowUnderPointer = getWindowUnderPointer(window, globalPos);
     QWindowsWindow *platformWindow = static_cast<QWindowsWindow *>(window->handle());
@@ -788,7 +803,7 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window, HWND hwnd, QtW
         m_windowUnderPointer = currentWindowUnderPointer;
     }
 
-    const Qt::MouseButtons mouseButtons = queryMouseButtons();
+    const Qt::MouseButtons mouseButtons = mouseButtonsFromKeyState(msg.wParam);
 
     if (!discardEvent)
         QWindowSystemInterface::handleMouseEvent(window, localPos, globalPos, mouseButtons, Qt::NoButton, QEvent::MouseMove,
diff --git a/src/plugins/platforms/windows/qwindowspointerhandler.h b/src/plugins/platforms/windows/qwindowspointerhandler.h
index c4d0e0ce4a..3861ebf919 100644
--- a/src/plugins/platforms/windows/qwindowspointerhandler.h
+++ b/src/plugins/platforms/windows/qwindowspointerhandler.h
@@ -61,7 +61,6 @@ public:
     bool translateMouseEvent(QWindow *window, HWND hwnd, QtWindows::WindowsEventType et, MSG msg, LRESULT *result);
     QTouchDevice *touchDevice() const { return m_touchDevice; }
     QTouchDevice *ensureTouchDevice();
-    Qt::MouseButtons queryMouseButtons();
     QWindow *windowUnderMouse() const { return m_windowUnderPointer.data(); }
     void clearWindowUnderMouse() { m_windowUnderPointer = nullptr; }