From df32dee74c5cb179278f142c837134438e90eabb Mon Sep 17 00:00:00 2001
From: "Maurizio M. Gavioli" <mmg@kwannon.(none)>
Date: Sat, 27 Apr 2013 00:42:55 +0200
Subject: [PATCH] Fix #20826 - Numpad numbers no longer work to select note
 duration.

Fixed by blocking the creation (and pooling) of QAction creation for shortcuts with multiple alternatives in different states (like the 'common' and TAB-specific variants of "pad-note-..." shortcuts)

A rather detailed description of the implementation (regarding both the original, faulty, implementation and this fix) has been added to the mscore/shortcut.h file
---
 mscore/musescore.cpp |  3 ++-
 mscore/shortcut.cpp  |  3 +++
 mscore/shortcut.h    | 48 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/mscore/musescore.cpp b/mscore/musescore.cpp
index c67cbfafef..c3e427602b 100644
--- a/mscore/musescore.cpp
+++ b/mscore/musescore.cpp
@@ -491,7 +491,8 @@ MuseScore::MuseScore()
       ag->setExclusive(false);
       foreach(const Shortcut* s, Shortcut::shortcuts()) {
             QAction* a = s->action();
-            ag->addAction(a);
+            if (a)
+                  ag->addAction(a);
             }
       addActions(ag->actions());
       connect(ag, SIGNAL(triggered(QAction*)), SLOT(cmd(QAction*)));
diff --git a/mscore/shortcut.cpp b/mscore/shortcut.cpp
index c6365d0b48..0e0cfcacf6 100644
--- a/mscore/shortcut.cpp
+++ b/mscore/shortcut.cpp
@@ -235,6 +235,9 @@ QAction* Shortcut::action() const
       if (_action)
             return _action;
 
+      if (_state == STATE_NEVER)
+            return 0;
+
       _action = new QAction(_text, 0);
       _action->setData(_key);
 
diff --git a/mscore/shortcut.h b/mscore/shortcut.h
index 868f740434..0f1f51bb79 100644
--- a/mscore/shortcut.h
+++ b/mscore/shortcut.h
@@ -14,6 +14,54 @@
 #ifndef __SHORTCUT_H__
 #define __SHORTCUT_H__
 
+/*---------------------------------------------------------
+NOTE ON ARCHITECTURE
+
+The Shortcut class describes the basic configurable shortcut element.
+'Real' data are contained in 2 static member variables:
+
+1) sc[], an array of Shortcut: contains the default, built-in data for each shortcut
+      except the key sequences; it is initialized at startup (code at the begining of
+      mscore/actions.cpp)
+2) _shortcuts, a QMap using the shortcut xml tag name as hash value: is initialized from
+      data in sc via a call to Shortcut::init() in program main() (mscore/musescore.cpp).
+      This also load actual key sequences either from an external, hard-coded, file with
+      user customizations or from a resource (<= mscore/data/shortcuts.xml), if there are
+      no customizations.
+      Later during startup, QAction's are derived from each of its elements and pooled
+      in a single QActionGroup during MuseScore::MuseScore() costructor (mscore/musescore.cpp)
+
+ShortcutFlags:
+      To be documented
+
+State flags:
+
+Defined in mscore/global.h (ScoreState enum): each shortcut is ignored if its _flags mask
+does not include the current score state. This is different from (and additional to)
+QAction processing performed by the Qt framework and happens only after the action has
+been forwarded to the application (the action must be enabled).
+
+The STATE_NEVER requires an explanation. It has been introduced to mark shortcuts
+which need to be recorded (and possibly customized) but are never used directly.
+Currently, this applies to a number of shortcuts which:
+- have been split between a common and a TAB-specific variant AND
+- are linked to tool bar buttons or menu items
+If QAction's are created for both, Qt blocks either as duplicate; in addition, the button
+or menu item may become disabled on state change. The currently implemented solution is
+to create a QAction only for one of them (the common one) and swap the key sequences when
+entering or leaving the relevant state.
+Swapping is implemented in MuseScore::changeState() (mscore/musescore.cpp).
+QAction creation for the 'other' shortcut is blocked in Shortcut::action() (mscore/shortcut.cpp).
+
+This means that Shortcut::action() may return 0. When scanning the whole
+shortcuts[] array, this has to be taken into account; currently it happens in two
+cases:
+- in MuseScore::MuseScore() constructor (mscore/musescore.cpp)
+- in MuseScore::changeState() method (mscore/musescore.cpp)
+
+Shortcuts marked with the STATE_NEVER state should NEVER used directly as shortcuts!
+---------------------------------------------------------*/
+
 class Xml;
 class XmlReader;