Fixed dead keys on MS Windows

Since Qt4, there is a bug which causes Qt to drop dead key modifiers
(like graves and acutes) if the user types enough fast on MS Windows.

This happens because of an extrange behavior of Windows, which drops
dead keys on ToUnicode() calls.

This patch tries to workaround that.

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

Change-Id: Ifdde25817743194fd5c0b7533c27f46a7a108ca4
Reviewed-by: Friedemann.Kleint@digia.com
Reviewed-by: oliver.wolff@digia.com
Reviewed-by: marc.mutz@kdab.com
Reviewed-by: bjoern.breitmeyer@kdab.com
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/src/plugins/platforms/windows/qwindowskeymapper.cpp b/src/plugins/platforms/windows/qwindowskeymapper.cpp
index 5a11aee802..f64593badc 100644
--- a/src/plugins/platforms/windows/qwindowskeymapper.cpp
+++ b/src/plugins/platforms/windows/qwindowskeymapper.cpp
@@ -856,9 +856,15 @@ bool QWindowsKeyMapper::translateKeyEventInternal(QWindow *window, const MSG &ms
     if (isNumpad && (nModifiers & AltAny)) {
         code = winceKeyBend(msg.wParam);
     } else if (!isDeadKey) {
-        unsigned char kbdBuffer[256]; // Will hold the complete keyboard state
-        GetKeyboardState(kbdBuffer);
-        code = toKeyOrUnicode(msg.wParam, scancode, kbdBuffer);
+        // 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.
+
+        // 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);
     }
 
     // Invert state logic: