[LyX/master] Do not blindly insert ubound Alt- keybindings.

[Juergen Spitzmueller]

commit 301782fad755922812550986b0fad07898b1c8a0
Author: Juergen Spitzmueller <sp...@lyx.org>
Date:   Wed May 13 14:54:52 2015 +0200

    Do not blindly insert ubound Alt-<letter> keybindings.
    
    Fixes: #5575

diff --git a/src/frontends/qt4/GuiApplication.cpp 
b/src/frontends/qt4/GuiApplication.cpp
index 160df4a..eaf33c4 100644
--- a/src/frontends/qt4/GuiApplication.cpp
+++ b/src/frontends/qt4/GuiApplication.cpp
@@ -2128,6 +2128,11 @@ void GuiApplication::processKeySym(KeySymbol const & 
keysym, KeyModifier state)
        }
 
        if (func.action() == LFUN_UNKNOWN_ACTION) {
+               if (state & AltModifier) {
+                       current_view_->message(_("Unknown function."));
+                       current_view_->restartCursor();
+                       return;
+               }
                // Hmm, we didn't match any of the keysequences. See
                // if it's normal insertable text not already covered
                // by a binding
@@ -2138,6 +2143,9 @@ void GuiApplication::processKeySym(KeySymbol const & 
keysym, KeyModifier state)
                                LYXERR(Debug::KEY, "Non-printable character! 
Omitting.");
                                return;
                        }
+                       // FIXME: Is this really needed? If not, we could  
simply go with
+                       // with the else part for LFUN_UNKNOWN_ACTION
+                       // (see discussion at #5575)
                        LYXERR(Debug::KEY, "isText() is true, inserting.");
                        func = FuncRequest(LFUN_SELF_INSERT,
                                           FuncRequest::KEYBOARD);