Fix virtual key mapping on MS Windows

In order to map MS Windows virtual keys to Qt keys without messing with
dead keys now I use the built-in keyMap structure of QWindowsKeyMapper
and assert every cell in the keymap is properly updated.

In order to guarantee this even when the user changes the keyboard
layout, WndProc now manages the WM_INPUTLANGCHANGE message, which is
handled by QWindowsKeyMapper, resetting the layout structure.

I don't fully understand yet some things about QWindowsKeyMapper, i.e.
how QWindowsKeyMapper::updatePossibleKeyCodes workarounds the dead key
issue with ToAscii; but it seems to work fine in all the tests I've
done. Any further testing is highly appreciated, though.

[ChangeLog][[QtGui][Platform Specific Changes][Windows] Fixed virtual key
mapping on Windows.

Task-number: QTBUG-33409
Task-number: QTBUG-8764
Task-number: QTBUG-10032

Change-Id: I4f7709a90906b03f4504deea1ff5c361e9f94b3f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/corelib/kernel/qcoreapplication_win.cpp

@@ -831,6 +831,11 @@ QString decodeMSG(const MSG& msg)
             }
             break;
 #endif
+#ifdef WM_INPUTLANGCHANGE
+        case WM_INPUTLANGCHANGE:
+            parameters = QStringLiteral("Keyboard layout changed");
+            break;
+#endif // WM_INPUTLANGCHANGE
 #ifdef WM_NCACTIVATE
         case WM_NCACTIVATE:
             {

src/plugins/platforms/windows/qtwindowsglobal.h

@@ -93,6 +93,7 @@ enum WindowsEventType // Simplify event types
     NonClientHitTest = NonClientEventFlag + 2,
     KeyEvent = KeyEventFlag + 1,
     KeyDownEvent = KeyEventFlag + KeyDownEventFlag + 1,
+    KeyboardLayoutChangeEvent = KeyEventFlag + 2,
     InputMethodKeyEvent = InputMethodEventFlag + KeyEventFlag + 1,
     InputMethodKeyDownEvent = InputMethodEventFlag + KeyEventFlag + KeyDownEventFlag + 1,
     ClipboardEvent = ClipboardEventFlag + 1,
@@ -165,6 +166,10 @@ inline QtWindows::WindowsEventType windowsEventType(UINT message, WPARAM wParamI
         return QtWindows::InputMethodKeyEvent;
     case WM_IME_KEYDOWN:
         return QtWindows::InputMethodKeyDownEvent;
+#ifdef WM_INPUTLANGCHANGE
+    case WM_INPUTLANGCHANGE:
+        return QtWindows::KeyboardLayoutChangeEvent;
+#endif // WM_INPUTLANGCHANGE
     case WM_TOUCH:
         return QtWindows::TouchEvent;
     case WM_CHANGECBCHAIN:

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -842,6 +842,7 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
     case QtWindows::KeyEvent:
     case QtWindows::InputMethodKeyEvent:
     case QtWindows::InputMethodKeyDownEvent:
+    case QtWindows::KeyboardLayoutChangeEvent:
 #if !defined(Q_OS_WINCE) && !defined(QT_NO_SESSIONMANAGER)
         return platformSessionManager()->isInterractionBlocked() ? true : d->m_keyMapper.translateKeyEvent(platformWindow->window(), hwnd, msg, result);
 #else

src/plugins/platforms/windows/qwindowskeymapper.cpp

@@ -574,7 +574,7 @@ void QWindowsKeyMapper::updateKeyMap(const MSG &msg)
 {
     unsigned char kbdBuffer[256]; // Will hold the complete keyboard state
     GetKeyboardState(kbdBuffer);
-    quint32 scancode = (msg.lParam >> 16) & 0xfff;
+    const quint32 scancode = (msg.lParam >> 16) & 0xff;
     updatePossibleKeyCodes(kbdBuffer, scancode, msg.wParam);
 }
 
@@ -742,12 +742,21 @@ bool QWindowsKeyMapper::translateKeyEvent(QWindow *widget, HWND hwnd,
                                           const MSG &msg, LRESULT *result)
 {
     *result = 0;
+
+    // Reset layout map when system keyboard layout is changed
+    if (msg.message == WM_INPUTLANGCHANGE) {
+        deleteLayouts();
+        return true;
+    }
+
+    // Add this key to the keymap if it is not present yet.
+    updateKeyMap(msg);
+
     MSG peekedMsg;
     // consume dead chars?(for example, typing '`','a' resulting in a-accent).
     if (PeekMessage(&peekedMsg, hwnd, 0, 0, PM_NOREMOVE) && peekedMsg.message == WM_DEADCHAR)
         return true;
-    if (msg.message == WM_KEYDOWN || msg.message == WM_SYSKEYDOWN)
-        updateKeyMap(msg);
+
     return translateKeyEventInternal(widget, msg, false);
 }
 
@@ -755,9 +764,8 @@ bool QWindowsKeyMapper::translateKeyEventInternal(QWindow *window, const MSG &ms
 {
     const int  msgType = msg.message;
 
-    const quint32 scancode = (msg.lParam >> 16) & 0xfff;
-    const quint32 vk_key = MapVirtualKey(scancode, 1);
-    const bool isNumpad = (msg.wParam >= VK_NUMPAD0 && msg.wParam <= VK_NUMPAD9);
+    const quint32 scancode = (msg.lParam >> 16) & 0xff;
+    const quint32 vk_key = msg.wParam;
     quint32 nModifiers = 0;
 
     QWindow *receiver = m_keyGrabber ? m_keyGrabber : window;
@@ -786,10 +794,6 @@ bool QWindowsKeyMapper::translateKeyEventInternal(QWindow *window, const MSG &ms
     state |= (nModifiers & AltAny ? int(Qt::AltModifier) : 0);
     state |= (nModifiers & MetaAny ? int(Qt::MetaModifier) : 0);
 
-    // Now we know enough to either have MapVirtualKey or our own keymap tell us if it's a deadkey
-    const bool isDeadKey = isADeadKey(msg.wParam, state)
-                     || MapVirtualKey(msg.wParam, 2) & 0x80000000;
-
     // A multi-character key or a Input method character
     // not found by our look-ahead
     if (msgType == WM_CHAR || msgType == WM_IME_CHAR) {
@@ -849,23 +853,12 @@ bool QWindowsKeyMapper::translateKeyEventInternal(QWindow *window, const MSG &ms
         return true;
 
     // Translate VK_* (native) -> Key_* (Qt) keys
-    // If it's a dead key, we cannot use the toKeyOrUnicode() function, since that will change
-    // the internal state of the keyboard driver, resulting in that dead keys no longer works.
-    // ..also if we're typing numbers on the keypad, while holding down the Alt modifier.
-    int code = 0;
-    if (isNumpad && (nModifiers & AltAny)) {
-        code = winceKeyBend(msg.wParam);
-    } else if (!isDeadKey) {
-        // QTBUG-8764, QTBUG-10032
-        // Can't call toKeyOrUnicode because that would call ToUnicode, and, if a dead key
-        // is pressed at the moment, Windows would NOT use it to compose a character for the next
-        // WM_CHAR event.
+    int modifiersIndex = 0;
+    modifiersIndex |= (nModifiers & ShiftAny ? 0x1 : 0);
+    modifiersIndex |= (nModifiers & ControlAny ? 0x2 : 0);
+    modifiersIndex |= (nModifiers & AltAny ? 0x4 : 0);
 
-        // Instead, use MapVirtualKey, which will provide adequate values.
-        code = MapVirtualKey(msg.wParam, MAPVK_VK_TO_CHAR);
-        if (code < 0x20 || code == 0x7f) // The same logic as in toKeyOrUnicode()
-            code = winceKeyBend(msg.wParam);
-    }
+    int code = keyLayout[vk_key].qtKey[modifiersIndex];
 
     // Invert state logic:
     // If the key actually pressed is a modifier key, then we remove its modifier key from the