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

Conflicts:
	src/plugins/platforms/windows/qwindowskeymapper.cpp

Change-Id: Ifdde25817743194fd5c0b7533c27f46a7a108ca4
(cherry picked from commit 5d2bb24cc90194a3458f8741e30ae7afe0b45f5c)
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/src/gui/kernel/qkeymapper_win.cpp b/src/gui/kernel/qkeymapper_win.cpp
index 5145699..b0931b0 100644
--- a/src/gui/kernel/qkeymapper_win.cpp
+++ b/src/gui/kernel/qkeymapper_win.cpp
@@ -925,9 +925,15 @@ bool QKeyMapperPrivate::translateKeyEvent(QWidget *widget, const MSG &msg, bool
         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: