Windows: Add support for horizontal scroll on some touchpads.

While most (all?) touchpads send WM_MOUSEWHEEL for vertical scroll
the story is quite different for horizontal scroll. Some of them
send WM_HSCROLL instead of WM_MOUSEHWHEEL.

Some of them even send left/right key event but those are lost cases.

Task-number: QTBUG-45120
Change-Id: I3bf86e25a6f4f3ba03ac7e89a23f4b7bc432f2de
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

src/plugins/platforms/windows/qtwindowsglobal.h

@@ -57,7 +57,8 @@ enum
     TouchEventFlag = 0x400000,
     ClipboardEventFlag = 0x800000,
     ApplicationEventFlag = 0x1000000,
-    ThemingEventFlag = 0x2000000
+    ThemingEventFlag = 0x2000000,
+    GenericEventFlag = 0x4000000, // Misc
 };
 
 enum WindowsEventType // Simplify event types
@@ -108,6 +109,7 @@ enum WindowsEventType // Simplify event types
     CompositionSettingsChanged = ThemingEventFlag + 2,
     DisplayChangedEvent = 437,
     SettingChangedEvent = DisplayChangedEvent + 1,
+    ScrollEvent = GenericEventFlag + 1,
     ContextMenu = 123,
     GestureEvent = 124,
     UnknownEvent = 542
@@ -145,6 +147,8 @@ inline QtWindows::WindowsEventType windowsEventType(UINT message, WPARAM wParamI
         return QtWindows::CursorEvent;
     case WM_MOUSELEAVE:
         return QtWindows::MouseEvent;
+    case WM_HSCROLL:
+        return QtWindows::ScrollEvent;
     case WM_MOUSEWHEEL:
     case WM_MOUSEHWHEEL:
         return QtWindows::MouseWheelEvent;

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -1031,6 +1031,12 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
             QWindowsWindow::baseWindowOf(platformWindow->window())->applyCursor();
             return true;
         }
+#endif
+    case QtWindows::ScrollEvent:
+#if !defined(Q_OS_WINCE) && !defined(QT_NO_SESSIONMANAGER)
+        return platformSessionManager()->isInteractionBlocked() ? true : d->m_mouseHandler.translateScrollEvent(platformWindow->window(), hwnd, msg, result);
+#else
+        return d->m_mouseHandler.translateScrollEvent(platformWindow->window(), hwnd, msg, result);
 #endif
     case QtWindows::MouseWheelEvent:
     case QtWindows::MouseEvent:

src/plugins/platforms/windows/qwindowsmousehandler.cpp

@@ -42,6 +42,7 @@
 #include <QtGui/QGuiApplication>
 #include <QtGui/QScreen>
 #include <QtGui/QWindow>
+#include <QtGui/QCursor>
 
 #include <QtCore/QDebug>
 #include <QtCore/QScopedArrayPointer>
@@ -375,6 +376,31 @@ static bool isValidWheelReceiver(QWindow *candidate)
     return false;
 }
 
+static void redirectWheelEvent(QWindow *window, const QPoint &globalPos, int delta,
+                               Qt::Orientation orientation, Qt::KeyboardModifiers mods)
+{
+    // 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.
+
+    QWindow *receiver = QWindowsScreen::windowAt(globalPos, CWP_SKIPINVISIBLE);
+    bool handleEvent = true;
+    if (!isValidWheelReceiver(receiver)) {
+        receiver = window;
+        if (!isValidWheelReceiver(receiver))
+            handleEvent = false;
+    }
+
+    if (handleEvent) {
+        const QPoint posDip = QWindowsGeometryHint::mapFromGlobal(receiver, globalPos) / QWindowsScaling::factor();
+        QWindowSystemInterface::handleWheelEvent(receiver,
+                                                 posDip, globalPos / QWindowsScaling::factor(),
+                                                 delta / QWindowsScaling::factor(),
+                                                 orientation, mods);
+    }
+}
+
 bool QWindowsMouseHandler::translateMouseWheelEvent(QWindow *window, HWND,
                                                     MSG msg, LRESULT *)
 {
@@ -397,26 +423,39 @@ 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));
-    QWindow *receiver = QWindowsScreen::windowAt(globalPos, CWP_SKIPINVISIBLE);
-    bool handleEvent = true;
-    if (!isValidWheelReceiver(receiver)) {
-        receiver = window;
-        if (!isValidWheelReceiver(receiver))
-            handleEvent = false;
+    redirectWheelEvent(window, globalPos, delta, orientation, mods);
+
+    return true;
+}
+
+bool QWindowsMouseHandler::translateScrollEvent(QWindow *window, HWND,
+                                                MSG msg, LRESULT *)
+{
+    // This is a workaround against some touchpads that send WM_HSCROLL instead of WM_MOUSEHWHEEL.
+    // We could also handle vertical scroll here but there's no reason to, there's no bug for vertical
+    // (broken vertical scroll would have been noticed long time ago), so lets keep the change small
+    // and minimize the chance for regressions.
+
+    int delta = 0;
+    switch (LOWORD(msg.wParam)) {
+    case SB_LINELEFT:
+        delta = 120;
+        break;
+    case SB_LINERIGHT:
+        delta = -120;
+        break;
+    case SB_PAGELEFT:
+        delta = 240;
+        break;
+    case SB_PAGERIGHT:
+        delta = -240;
+        break;
+    default:
+        return false;
     }
 
-    if (handleEvent) {
-        const QPoint posDip = QWindowsGeometryHint::mapFromGlobal(receiver, globalPos) / QWindowsScaling::factor();
-        QWindowSystemInterface::handleWheelEvent(receiver,
-                                                 posDip, globalPos / QWindowsScaling::factor(),
-                                                 delta / QWindowsScaling::factor(),
-                                                 orientation, mods);
-    }
+    redirectWheelEvent(window, QCursor::pos(), delta, Qt::Horizontal, Qt::NoModifier);
 
     return true;
 }

src/plugins/platforms/windows/qwindowsmousehandler.h

@@ -59,6 +59,8 @@ public:
     bool translateTouchEvent(QWindow *widget, HWND hwnd,
                              QtWindows::WindowsEventType t, MSG msg,
                              LRESULT *result);
+    bool translateScrollEvent(QWindow *window, HWND hwnd,
+                              MSG msg, LRESULT *result);
 
     static inline Qt::MouseButtons keyStateToMouseButtons(int);
     static inline Qt::KeyboardModifiers keyStateToModifiers(int);