Windows QPA: Support "press and hold for right-clicking"

Windows sends a fake WM_RBUTTONUP/WM_RBUTTONDOWN when the user presses
and holds the pen/finger on a tablet/touchscreen, e.g., in order to
show a context menu. Windows only sends already synthesized legacy
mouse messages for this condition, instead of anything detectable in
the pointer messages. So we need to handle these legacy messages in the
Windows QPA.

Task-number: QTBUG-36162
Change-Id: Ia93c423601e2e8a8baac3f9b7791bf8a3113885a
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 39 insertions, 15 deletions

diff --git a/src/plugins/platforms/windows/qwindowspointerhandler.cpp b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
index be67eb0248..e428a8cf63 100644
--- a/src/plugins/platforms/windows/qwindowspointerhandler.cpp
+++ b/src/plugins/platforms/windows/qwindowspointerhandler.cpp
@@ -200,6 +200,8 @@ bool QWindowsPointerHandler::translatePointerEvent(QWindow *window, HWND hwnd, Q
         return false;
     }
 
+    m_lastPointerType = pointerType;
+
     // Handle non-client pen/touch as generic mouse events for compatibility with QDockWindow.
     if ((pointerType == QT_PT_TOUCH || pointerType == QT_PT_PEN) && (et & QtWindows::NonClientEventFlag)) {
         POINTER_INFO pointerInfo;
@@ -838,6 +840,16 @@ bool QWindowsPointerHandler::translatePenEvent(QWindow *window, HWND hwnd, QtWin
 #endif
 }
 
+static inline bool isMouseEventSynthesizedFromPenOrTouch()
+{
+    // For details, see
+    // https://docs.microsoft.com/en-us/windows/desktop/tablet/system-events-and-mouse-messages
+    const LONG_PTR SIGNATURE_MASK = 0xFFFFFF00;
+    const LONG_PTR MI_WP_SIGNATURE = 0xFF515700;
+
+    return ((::GetMessageExtraInfo() & SIGNATURE_MASK) == MI_WP_SIGNATURE);
+}
+
 // Process old-style mouse messages here.
 bool QWindowsPointerHandler::translateMouseEvent(QWindow *window, HWND hwnd, QtWindows::WindowsEventType et, MSG msg, LRESULT *result)
 {
@@ -846,15 +858,6 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window, HWND hwnd, QtW
     flushTabletEvents();
 
     *result = 0;
-    if (et != QtWindows::MouseWheelEvent && msg.message != WM_MOUSELEAVE && msg.message != WM_MOUSEMOVE)
-        return false;
-
-    // Ignore messages synthesized from touch/pen (only use them for flushing queues).
-    const quint64 signatureMask = 0xffffff00;
-    const quint64 miWpSignature = 0xff515700;
-    const quint64 extraInfo = quint64(GetMessageExtraInfo());
-    if ((extraInfo & signatureMask) == miWpSignature)
-        return false;
 
     const QPoint eventPos(GET_X_LPARAM(msg.lParam), GET_Y_LPARAM(msg.lParam));
     QPoint localPos;
@@ -868,6 +871,26 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window, HWND hwnd, QtW
     }
 
     const Qt::KeyboardModifiers keyModifiers = QWindowsKeyMapper::queryKeyboardModifiers();
+    const Qt::MouseButtons mouseButtons = mouseButtonsFromKeyState(msg.wParam);
+
+    // Handle "press and hold for right-clicking".
+    // We have to synthesize it here as it only comes from Windows as a fake RMB.
+    // MS docs say we could use bit 7 from extraInfo to distinguish pen from touch,
+    // but on the Surface it is set for both. So we use the last pointer type.
+    if (isMouseEventSynthesizedFromPenOrTouch()) {
+        if ((msg.message == WM_RBUTTONDOWN || msg.message == WM_RBUTTONUP)
+            && (((m_lastPointerType == QT_PT_PEN)
+                 && QCoreApplication::testAttribute(Qt::AA_SynthesizeMouseForUnhandledTabletEvents))
+                || ((m_lastPointerType == QT_PT_TOUCH)
+                    && QCoreApplication::testAttribute(Qt::AA_SynthesizeMouseForUnhandledTouchEvents)))) {
+            QWindowSystemInterface::handleMouseEvent(window, localPos, globalPos, mouseButtons, Qt::RightButton,
+                                                     (msg.message == WM_RBUTTONDOWN) ? QEvent::MouseButtonPress
+                                                                                     : QEvent::MouseButtonRelease,
+                                                     keyModifiers, Qt::MouseEventSynthesizedBySystem);
+        }
+        // Messages synthesized from touch/pen are only used for flushing queues and press&hold.
+        return false;
+    }
 
     if (et == QtWindows::MouseWheelEvent) {
 
@@ -888,6 +911,7 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window, HWND hwnd, QtW
     }
 
     if (msg.message == WM_MOUSELEAVE) {
+
         if (window == m_currentWindow) {
             QWindow *leaveTarget = m_windowUnderPointer ? m_windowUnderPointer : m_currentWindow;
             qCDebug(lcQpaEvents) << "Leaving window " << leaveTarget;
@@ -895,14 +919,13 @@ bool QWindowsPointerHandler::translateMouseEvent(QWindow *window, HWND hwnd, QtW
             m_windowUnderPointer = nullptr;
             m_currentWindow = nullptr;
         }
-        return false;
-    }
 
-    QWindow *currentWindowUnderPointer = getWindowUnderPointer(window, globalPos);
-    const Qt::MouseButtons mouseButtons = mouseButtonsFromKeyState(msg.wParam);
+    } else if (msg.message == WM_MOUSEMOVE) {
 
-    handleCaptureRelease(window, currentWindowUnderPointer, hwnd, QEvent::MouseMove, mouseButtons);
-    handleEnterLeave(window, currentWindowUnderPointer, globalPos);
+        QWindow *currentWindowUnderPointer = getWindowUnderPointer(window, globalPos);
+        handleCaptureRelease(window, currentWindowUnderPointer, hwnd, QEvent::MouseMove, mouseButtons);
+        handleEnterLeave(window, currentWindowUnderPointer, globalPos);
+    }
     return false;
 }
 
diff --git a/src/plugins/platforms/windows/qwindowspointerhandler.h b/src/plugins/platforms/windows/qwindowspointerhandler.h
index a586c7863c..ec3179e821 100644
--- a/src/plugins/platforms/windows/qwindowspointerhandler.h
+++ b/src/plugins/platforms/windows/qwindowspointerhandler.h
@@ -78,6 +78,7 @@ private:
     QPointer<QWindow> m_currentWindow;
     QWindow *m_previousCaptureWindow = nullptr;
     bool m_needsEnterOnPointerUpdate = false;
+    DWORD m_lastPointerType = 0;
 };
 
 QT_END_NAMESPACE