[LyX/master] Fix #5575 also on Windows.

[Enrico Forestieri]

commit 324abefd5317e91a2e0a517676e7a6f37fa36015
Author: Enrico Forestieri <for...@lyx.org>
Date:   Sat May 16 23:36:40 2015 +0200

    Fix #5575 also on Windows.

diff --git a/src/frontends/qt4/GuiApplication.cpp 
b/src/frontends/qt4/GuiApplication.cpp
index 6640ce3..3957a2a 100644
--- a/src/frontends/qt4/GuiApplication.cpp
+++ b/src/frontends/qt4/GuiApplication.cpp
@@ -2141,16 +2141,19 @@ void GuiApplication::processKeySym(KeySymbol const & 
keysym, KeyModifier state)
                        }
                        // If a non-Shift Modifier is used we have a non-bound 
key sequence
                        // (such as Alt+j = j). This should be omitted (#5575).
-                       // FIXME: On Windows, the AltModifier and ShiftModifer 
is also
-                       // set when AltGr is pressed. Therefore, the check 
below cannot be used
-                       // since it breaks AltGr-bound symbols (see #5575 for 
details).
-#if !defined(_WIN32)
-                       if (state & AltModifier || state & ControlModifier || 
state & MetaModifier) {
+                       // On Windows, AltModifier and ControlModifier are both
+                       // set when AltGr is pressed. Therefore, in order to not
+                       // break AltGr-bound symbols (see #5575 for details),
+                       // unbound Ctrl+Alt key sequences are allowed.
+                       if ((state & AltModifier || state & ControlModifier || 
state & MetaModifier)
+#if defined(Q_OS_WIN) || defined(Q_CYGWIN_WIN)
+                           && !(state & AltModifier && state & ControlModifier)
+#endif
+                           ) {
                                current_view_->message(_("Unknown function."));
                                current_view_->restartCursor();
                                return;
                        }
-#endif
                        // Since all checks above were passed, we now really 
have text that
                        // is to be inserted (e.g., AltGr-bound symbols). Thus 
change the
                        // func to LFUN_SELF_INSERT and thus cause the text to 
be inserted