Developer CD Series 1997 January: Mac OS SDK/Dev.CD Jan 97 SDK2.toast/Development Kits (Disc 2)/OpenDoc/OpenDoc Development/Debugging Support/OpenDoc™ Source Code/UI/Undo.cpp

C/C++ Source or Header | 1996-08-28 | 59.0 KB | 2,151 lines | [TEXT/MPS ]

/*
    File:        Undo.cpp

    Contains:    Implementation for Undo class

    Owned by:    Nick Pilch

    Copyright:    © 1994 - 1996 by Apple Computer, Inc., all rights reserved.

    Change History (most recent first):

         <7>     8/13/96    VL        1372870: Not dispose of memory in
                                    UndoAction destructor if process has gone
                                    away. Added
                                    SystemUndo::ShouldStackBeCleared to check
                                    to see whether the first action(s) is still
                                    valid.
         <6>     6/18/96    NP        1267014, 1358481, 1347976, 1292558, 1266989
         <5>     5/24/96    jpa        1246074: SOM_CATCH --> SOM_TRY..SOM_ENDTRY
         <4>    .04.1996    NP        1316777: Machine hangs for one minute while
                                    dragging. 1328995: Mem leak. 1323304:
                                    actionData passed to part has _length == 0
         <3>    .04.1996    NP        1316777: Partiall fix race condition with
                                    the disposal notification process.

    To Do:
        Remove destructors where not needed.
    In Progress:

*/


#ifndef _PART_
#include "Part.xh"
#endif

//#ifndef _ORDCOLL_
//#include "OrdColl.h"
//#endif

#ifndef SOM_Module_OpenDoc_StdDefs_defined
#include "StdDefs.xh"
#endif

#ifndef _SEUTILS_
#include "SEUtils.h"
#endif

#ifndef _ODUTILS_
#include "ODUtils.h"
#endif

#ifndef _ITEXT_
#include "IText.h"
#endif

#define ODUndo_Class_Source
#define VARIABLE_MACROS
#include <Undo.xih>

#ifndef _EXCEPT_
#include <Except.h>
#endif

#ifndef _BARRAY_
#include <BArray.h>
#endif

//#ifndef _ODNEW_
//#include <ODNew.h>
//#endif

#ifndef _ODDEBUG_
#include "ODDebug.h"
#endif

//#ifndef _ODTYPES_
//#include "ODTypes.h"
//#endif

//#ifndef _PLFMDEF_
//#include "PlfmDef.h"
//#endif

//#ifndef _LIST_
//#include "List.h"
//#endif

#ifndef _ODMEMORY_
#include "ODMemory.h"
#endif

#ifndef __ERRORS__
#include <Errors.h>
#endif

#ifndef _ODDEBUG_
#include "ODDebug.h"
#endif

#ifndef _TEMPOBJ_
#include <TempObj.h>
#endif

#pragma segment ODUndo

/*
IMPLEMENTATION NOTES

System Heap allocations

Almost all memory allocations occur in the system heap.

I'm trying to use as little system heap memory as possible because putting
pointers into the system heap could be a bad idea (mem fragmentation).

UNDO AND REDO STACKS

The stacks are implemented with the UndoOrderedCollection class. The first item
in the collection represents the top of the stack.

MARKING

When asked to mark a stack that is empty, nothing is done. The code that removes
actions from a stack up to the last mark simply stops when it comes to the end
of a stack.

ADDCLIENT, ETC.

We need to use these functions to ensure the SystemUndo is freed when
the last OD document is closed. The memory associated with it will have gone
away.
*/

//==============================================================================
// Special new operator for the system heap that use NewPtrSys and
//    DisposePtr.
//==============================================================================

enum ODUndoMemoryAllocation
{
    kODSystemHeap
};

void* operator new(size_t size, ODUndoMemoryAllocation allocation);

void* operator new(size_t size, ODUndoMemoryAllocation allocation)
{
    void*    retVal;

    if (allocation == kODSystemHeap)
        retVal = NewPtrSys(size);
    else
        THROW(kODErrNotImplemented);

    return retVal;
}

boolean IsValidProcess(ProcessSerialNumber* psn);

boolean IsValidProcess(ProcessSerialNumber* psn)
{
    ProcessInfoRec info;
    info.processInfoLength = sizeof(ProcessInfoRec);
    info.processName = nil;
    info.processAppSpec = nil;

    return (GetProcessInformation(psn, &info) == noErr);
}


//==============================================================================
// Temporarily include new UndoOrderedCollection class that I can allocate in the
//    system heap. (May be longer than temporary.)
//==============================================================================



/////////////// BEGIN TEMP HACK



//==============================================================================
// UndoLink
//==============================================================================

class  UndoLink {
    public:
//        void* operator new(size_t size) {return NewPtrSys(size);}
        void operator delete(void* ptr) {DisposePtr((Ptr)ptr);}
        UndoLink();

        UndoLink(UndoLink* next, UndoLink* previous);

        UndoLink( const UndoLink& );

        ~UndoLink();

        UndoLink* GetNext() const                    {return fNext;}

        UndoLink* GetPrevious() const                {return fPrevious;}

    // The following operations are provided for efficiency, but DO NOT USE THEM
    // if there are any iterators active on a list. These operations don't bump
    // the list's fSeed and the iterators will not be able to detect that they
    // are out of sync!

        void  Remove( );

        void  AddBefore( UndoLink *aLink );

        void  AddAfter( UndoLink *aLink );

  //private-by-convention:

        void  SetNext(UndoLink* aLink)                {fNext = aLink;}

        void  SetPrevious(UndoLink* aLink)            {fPrevious = aLink;}

    private:

        UndoLink*        fNext;
        UndoLink*        fPrevious;
};


//==============================================================================
// UndoLinkedList
//==============================================================================


class UndoLinkedList {

    public:
        void operator delete(void* ptr) {DisposePtr((Ptr)ptr);}
          UndoLinkedList();

          ~UndoLinkedList();

          void            Remove(UndoLink&);

          void            AddFirst(UndoLink* link);

          UndoLink*            RemoveFirst();

          UndoLink*            First()                                            const;

protected:

        UndoLink            fSentinel;    // Marks the head & tail
        ODULong            fSeed;        // Used to detect out-of-sync iterators

        UndoLink*            GetSentinel( )
                                                {return &fSentinel;}
        const UndoLink*        GetSentinel( )                                    const
                                                {return &fSentinel;}
        ODBoolean        IsSentinel( const UndoLink* link )                    const
                                                {return link==this->GetSentinel();}
        ODBoolean        NotSentinel( const UndoLink* link )                    const
                                                {return link!=this->GetSentinel();}

private:
        friend class UndoLinkedListIterator;
};


//=====================================================================================
// UndoLinkedListIterator
//=====================================================================================

class UndoLinkedListIterator {

    public:

        UndoLinkedListIterator(UndoLinkedList*    list);

        ~UndoLinkedListIterator();

        UndoLink*            First();

        UndoLink*            Next();

        ODBoolean         IsNotComplete();

    private:

        UndoLinkedList*        fList;
        UndoLink*            fCurrent;
        UndoLink*            fNext;        // Used only when deleting while iterating
        UndoLink*             fPrevious;    // Used only when deleting while iterating
        UndoLink*            fSentinel;
        ODULong            fSeed;        // Used to detect out-of-sync iterators

};

//==============================================================================
// Scalar Types
//==============================================================================

typedef void* ElementType;

//=====================================================================================
// Class UndoValueLink - Definition
//=====================================================================================

class UndoValueLink : public UndoLink {

public:
                            UndoValueLink(ElementType value);
                    ~UndoValueLink();
        ElementType    GetValue()                        { return fValue;}
     void        SetValue(ElementType v)            { fValue = v;}

private:
    ElementType         fValue;
};

//=====================================================================================
// Class UndoOrderedCollection
//=====================================================================================

class UndoOrderedCollection
{

public:
    void operator delete(void* ptr) {DisposePtr((Ptr)ptr);}
    UndoOrderedCollection();
    UndoOrderedCollection(ODUndoMemoryAllocation where);
    ~UndoOrderedCollection();

     void    AddFirst(ElementType element);
     ElementType    First();
        // Returns kODNULL if there is no first element.
     ElementType    RemoveFirst();
        // Don't call if there are no elements. Crash will result.
     void    Remove(ElementType existing);
     void    RemoveAll();

        // Called from the destructor. Removes all elements, deleting the links
        // Does not delete the elements themselves

protected:
      UndoValueLink*     CreateNewLink(ElementType value) const;
      ODBoolean    ElementsMatch(ElementType v1,ElementType v2) const;
         // Does a pointer comparison by default

private:
    UndoLinkedList        fImplementation;
    ODUndoMemoryAllocation    fHeap; // if kODNULL, use default heap.

    friend class UndoOrderedCollectionIterator;
    friend class ListIterator;
};

//=====================================================================================
// Class UndoOrderedCollectionIterator
//=====================================================================================

class UndoOrderedCollectionIterator {
public:
    UndoOrderedCollectionIterator(UndoOrderedCollection* collection);
    ~UndoOrderedCollectionIterator();
    ElementType    First();
    ElementType    Next();
    ODBoolean    IsNotComplete();

private:
      UndoOrderedCollection*    fCollection;
    UndoLinkedListIterator    fImplementation;
};

//==============================================================================
// UndoLink
//==============================================================================



// Many of the simple link methods are inlines; see List.h for implementations.


//------------------------------------------------------------------------------
// UndoLink::UndoLink
//
// Constructor for UndoLink
//------------------------------------------------------------------------------

UndoLink::UndoLink()
{
    fNext = kODNULL;
    fPrevious = kODNULL;
}

//------------------------------------------------------------------------------
// UndoLink::UndoLink
//
// Constructor for UndoLink
//------------------------------------------------------------------------------

UndoLink::UndoLink(UndoLink* next, UndoLink* previous)
{
    fNext = next;
    fPrevious = previous;
}

//------------------------------------------------------------------------------
// UndoLink::UndoLink
//
// Copy constructor for UndoLink
//------------------------------------------------------------------------------

UndoLink::UndoLink( const UndoLink &link )
{
    fNext = link.fNext;
    fPrevious = link.fPrevious;
}

//------------------------------------------------------------------------------
// UndoLink::UndoLink
//
// Destructor for UndoLink
//------------------------------------------------------------------------------

UndoLink::~UndoLink()
{
}

//------------------------------------------------------------------------------
// UndoLink::Remove
//
// Remove a link from its list (if any). DO NOT call this directly if there are
// any iterators active on the list; use UndoLinkedList::Remove instead.
//------------------------------------------------------------------------------

void    UndoLink::Remove( )
{
    if( fPrevious )
        fPrevious->SetNext(fNext);
    if( fNext )
        fNext->SetPrevious(fPrevious);
    fNext = kODNULL;
    fPrevious = kODNULL;
}

//------------------------------------------------------------------------------
// UndoLink::AddBefore
//
// Add a link to a list before another link. It must not already be on any list.
// DO NOT call this directly if there are any iterators active on the list;
// use UndoLinkedList::Remove instead.
//------------------------------------------------------------------------------

void    UndoLink::AddBefore( UndoLink *link )
{
    ASSERT(link!=kODNULL,paramErr);
    WASSERT(fNext==kODNULL);
    WASSERT(fPrevious==kODNULL);
    fNext = link;
    fPrevious = link->GetPrevious();
    fPrevious->SetNext(this);
    fNext->SetPrevious(this);
}

//------------------------------------------------------------------------------
// UndoLink::AddAfter
//
// Add a link to a list after another link. It must not already be on any list.
// DO NOT call this directly if there are any iterators active on the list;
// use UndoLinkedList::Remove instead.
//------------------------------------------------------------------------------

void    UndoLink::AddAfter( UndoLink *link )
{
    ASSERT(link!=kODNULL,paramErr);
    WASSERT(fNext==kODNULL);
    WASSERT(fPrevious==kODNULL);
    fPrevious = link;
    fNext = link->GetNext();
    fPrevious->SetNext(this);
    fNext->SetPrevious(this);
}

//======================================================================================
// Class UndoLinkedList
//======================================================================================

//------------------------------------------------------------------------------
// UndoLinkedList::UndoLinkedList
//
// Constructor for UndoLinkedList
//------------------------------------------------------------------------------

UndoLinkedList::UndoLinkedList()
    :fSentinel(&fSentinel,&fSentinel),
     fSeed(0)
{
}

//------------------------------------------------------------------------------
// UndoLinkedList::~UndoLinkedList
//
// Destructor for UndoLinkedList
//------------------------------------------------------------------------------

UndoLinkedList::~UndoLinkedList()
{
    // The list does NOT delete all its links!
}

//------------------------------------------------------------------------------
// UndoLinkedList::Remove
//
// Description
//------------------------------------------------------------------------------

void    UndoLinkedList::Remove(UndoLink& aLink)
{
    fSeed++;
    aLink.Remove();
}

//------------------------------------------------------------------------------
// UndoLinkedList::RemoveFirst
//
// Description
//------------------------------------------------------------------------------

UndoLink* UndoLinkedList::RemoveFirst()
{
    UndoLink* old = fSentinel.GetNext();
    if (this->NotSentinel(old))
    {
        fSeed++;
        old->Remove();
        return old;
    }
    else
    {
        return kODNULL;
    }
}

//------------------------------------------------------------------------------
// UndoLinkedList::AddFirst
//
// Description
//------------------------------------------------------------------------------

void    UndoLinkedList::AddFirst(UndoLink* link)
{
    link->AddAfter(this->GetSentinel());
    fSeed++;
}

//------------------------------------------------------------------------------
// UndoLinkedList::First
//
// Description
//------------------------------------------------------------------------------

UndoLink*    UndoLinkedList::First()  const
{
    return this->NotSentinel(fSentinel.GetNext()) ? fSentinel.GetNext() : (UndoLink*) kODNULL;
}

//======================================================================================
// Class UndoLinkedListIterator
//======================================================================================

//------------------------------------------------------------------------------
// UndoLinkedListIterator::UndoLinkedListIterator
//
// Constructor for UndoLinkedListIterator
//------------------------------------------------------------------------------

UndoLinkedListIterator::UndoLinkedListIterator(UndoLinkedList* list)
{
    fList = list;
    fCurrent = kODNULL;
    fNext = kODNULL;
    fPrevious = kODNULL;
    fSentinel = &list->fSentinel;
    fSeed = fList->fSeed;
}

//------------------------------------------------------------------------------
// UndoLinkedListIterator::~UndoLinkedListIterator
//
// Destructor for UndoLinkedListIterator
//------------------------------------------------------------------------------

UndoLinkedListIterator::~UndoLinkedListIterator()
{
}

//------------------------------------------------------------------------------
// UndoLinkedListIterator::First
//
// Description
//------------------------------------------------------------------------------

UndoLink* UndoLinkedListIterator::First()
{
    if (fList == kODNULL)
        return kODNULL;

    if (fSeed != fList->fSeed)
        THROW(kODErrIteratorOutOfSync);

    fCurrent = fList->First();
    if (fCurrent == fSentinel)
        fCurrent = kODNULL;
    return fCurrent;
}

//------------------------------------------------------------------------------
// UndoLinkedListIterator::Next
//
// Description
//------------------------------------------------------------------------------

UndoLink* UndoLinkedListIterator::Next()
{
    if (fList == kODNULL)
        return kODNULL;

    if (fSeed != fList->fSeed)
        THROW(kODErrIteratorOutOfSync);

    if (fCurrent == kODNULL)
    {
        if ((fNext == kODNULL) && (fPrevious == kODNULL))    // Just starting out
        {
            return this->First();
        }
        else    // Just deleted
        {
            fCurrent = fNext;
            fPrevious = kODNULL;
            fNext = kODNULL;
        }
    }
    else
        fCurrent = fCurrent->GetNext();

    if (fCurrent == fSentinel)
        fCurrent = kODNULL;
    return fCurrent;
}

//------------------------------------------------------------------------------
// UndoLinkedListIterator::IsNotComplete
//
// Description
//------------------------------------------------------------------------------

ODBoolean UndoLinkedListIterator::IsNotComplete()
{
    return (fCurrent != kODNULL);
}

//======================================================================================
// Class UndoValueLink - Implementation
//======================================================================================

UndoValueLink::UndoValueLink(ElementType value)
{
    fValue = value;
}

UndoValueLink::~UndoValueLink()
{
}

//======================================================================================
// Class UndoOrderedCollection
//======================================================================================

//------------------------------------------------------------------------------
// UndoOrderedCollection::UndoOrderedCollection
//------------------------------------------------------------------------------

UndoOrderedCollection::UndoOrderedCollection()
{
    fHeap = kODSystemHeap;
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::UndoOrderedCollection
//------------------------------------------------------------------------------

UndoOrderedCollection::UndoOrderedCollection(ODUndoMemoryAllocation where)
{
    fHeap = where;
}

// UndoOrderedCollection::~UndoOrderedCollection
//------------------------------------------------------------------------------

UndoOrderedCollection::~UndoOrderedCollection()
{
    this->RemoveAll();
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::AddFirst
//------------------------------------------------------------------------------

void UndoOrderedCollection::AddFirst(ElementType element)
{
    UndoValueLink* newLink = this->CreateNewLink(element);
    fImplementation.AddFirst(newLink);
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::First
//------------------------------------------------------------------------------

ElementType UndoOrderedCollection::First()
{
    UndoValueLink* firstLink = (UndoValueLink*) fImplementation.First();
    return firstLink ? firstLink->GetValue() : (ElementType)kODNULL;
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::RemoveFirst
//------------------------------------------------------------------------------

ElementType    UndoOrderedCollection::RemoveFirst()
{
    UndoValueLink* aLink = (UndoValueLink*) fImplementation.RemoveFirst();
    ElementType value = aLink ? aLink->GetValue() : kODNULL;
    delete aLink;
    return value;
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::Remove
//------------------------------------------------------------------------------

void UndoOrderedCollection::Remove(ElementType existing)
{
    UndoLinkedListIterator iter(&fImplementation);
    UndoValueLink* aLink = (UndoValueLink*) iter.First();
    while (aLink != kODNULL)
    {
        ElementType v = ((UndoValueLink*) aLink)->GetValue();

        if (this->ElementsMatch(v,existing))
        {
            fImplementation.Remove(*aLink);
            delete aLink;
            aLink = kODNULL;
        }
        else
            aLink = (UndoValueLink*) iter.Next();
    }
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::RemoveAll
//------------------------------------------------------------------------------

void UndoOrderedCollection::RemoveAll()
{
    UndoLink* link = fImplementation.RemoveFirst();
    while (link != kODNULL)
    {
        delete link;
        link = fImplementation.RemoveFirst();
    }
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::CreateNewLink
//------------------------------------------------------------------------------

UndoValueLink*    UndoOrderedCollection::CreateNewLink(ElementType value) const
{
    return new (fHeap) UndoValueLink(value);
}

//------------------------------------------------------------------------------
// UndoOrderedCollection::ElementsMatch
//------------------------------------------------------------------------------

ODBoolean    UndoOrderedCollection::ElementsMatch(ElementType v1,ElementType v2) const
{
    return (v1 == v2);
}

//======================================================================================
// UndoOrderedCollectionIterator
//======================================================================================

//------------------------------------------------------------------------------
// UndoOrderedCollectionIterator::UndoOrderedCollectionIterator
//------------------------------------------------------------------------------

UndoOrderedCollectionIterator::UndoOrderedCollectionIterator(UndoOrderedCollection* collection)
    : fImplementation(collection ? &(collection->fImplementation) : (UndoLinkedList*)kODNULL)
{
    fCollection =  collection;
}

//------------------------------------------------------------------------------
// UndoOrderedCollectionIterator::~UndoOrderedCollectionIterator
//------------------------------------------------------------------------------

UndoOrderedCollectionIterator::~UndoOrderedCollectionIterator()
{
}

//------------------------------------------------------------------------------
// UndoOrderedCollectionIterator::First
//------------------------------------------------------------------------------

ElementType    UndoOrderedCollectionIterator::First()
{
    UndoValueLink* link = (UndoValueLink*) fImplementation.First();

    return link ? link->GetValue() : (ElementType)kODNULL;
}

//------------------------------------------------------------------------------
// UndoOrderedCollectionIterator::Next
//------------------------------------------------------------------------------

ElementType    UndoOrderedCollectionIterator::Next()
{
    UndoValueLink* link = (UndoValueLink*) fImplementation.Next();

    return link ? link->GetValue() : (ElementType)kODNULL;
}

//------------------------------------------------------------------------------
// UndoOrderedCollectionIterator::IsNotComplete
//------------------------------------------------------------------------------

ODBoolean    UndoOrderedCollectionIterator::IsNotComplete()
{
    return fImplementation.IsNotComplete();
}



/////////////// END TEMP HACK



//==============================================================================
// Constants
//==============================================================================

const OSType kUndoNotifyID = 'undo';
const OSType kRedoNotifyID = 'redo';
const OSType kDisposeActionNotifyID = 'del ';

const AEKeyword kDataPtrKeyword = 'data';
const AEKeyword kPartPtrKeyword = 'part';
const AEKeyword kDoneStateKeyword = 'done';

// A number of functions can share code. They pass along this enum to know
//    which course of action to take.
enum ODUndoRedoType
{
    kUndo,
    kRedo,
    kDispose
};

//==============================================================================
// Classes used in this file
//==============================================================================

class UndoAction;
class SystemUndo;

//==============================================================================
// Function Prototypes
//==============================================================================

const ODBoolean kODBringToFront = kODTrue;

static OSErr NotifyUndoOrRedoOrDispose(UndoAction* action,
                                                ODUndoRedoType which,
                                                ODBoolean bringToFront);
static OSErr NotifyUndo(UndoAction* action, ODBoolean bringToFront);
static OSErr NotifyRedo(UndoAction* action, ODBoolean bringToFront);
static OSErr NotifyDispose(UndoAction* action);
static SystemUndo *GetSystemUndo();
static ODBoolean SetSystemUndo(SystemUndo *systemUndo);

//==============================================================================
// Functions
//==============================================================================

// • Using ASLM we registered the system undo object with ASLM using the
// arbitration mechanism provided by ASLM. To eliminate our dependency on ASLM
// we are storing the system undo object in a global which is accessed by the
// following two functions. This is NOT a thread safe method for accessing the
// system undo!

//------------------------------------------------------------------------------
// GetSystemUndo
//------------------------------------------------------------------------------

#pragma lib_export on
extern SystemUndo* gSystemUndo;
#pragma lib_export off

static SystemUndo *GetSystemUndo()
{
    return gSystemUndo;
}

//------------------------------------------------------------------------------
// SetSystemUndo
//------------------------------------------------------------------------------

static ODBoolean SetSystemUndo(SystemUndo *systemUndo)
{
    gSystemUndo = systemUndo;
    return kODTrue;
}

//#pragma lib_export off

//==============================================================================
// Local Classes
//==============================================================================

//------------------------------------------------------------------------------

class UndoAction
{
  public:
        void operator delete(void* ptr) {DisposePtr((Ptr)ptr);}
    UndoAction(ODPart* whichPart, ODActionData* actionData,
                    ODActionType actionType, ODName* undoActionLabel,
                    ODName* redoActionLabel);
    ~UndoAction();

    ODPart*                fPart;
    ProcessSerialNumber    fProcessNum;
    ODActionData*        fActionData;
    ODActionType        fActionType;
    ODName*                fUndoActionLabel;
    ODName*                fRedoActionLabel;
    ODBoolean            fMark;
    ODDoneState            fDoneState;
};

//------------------------------------------------------------------------------
// UndoAction::UndoAction
//
//    This constructor may throw an error, but it's OK because there is nothing
//    to deallocate in the destructor.
//------------------------------------------------------------------------------

UndoAction::UndoAction(ODPart* whichPart,
                                    ODActionData* actionData,
                                    ODActionType actionType,
                                    ODName* undoActionLabel,
                                    ODName* redoActionLabel)
{
    fPart = whichPart;
    THROW_IF_ERROR(GetCurrentProcess(&fProcessNum));
    fActionData = actionData;
    fActionType = actionType;
    fUndoActionLabel = undoActionLabel;
    fRedoActionLabel = redoActionLabel;
    fMark = kODFalse;
    fDoneState = kODDone;
}

//------------------------------------------------------------------------------
// UndoAction::~UndoAction
//
//    Notify owning part owning fActionData to dipose of any associated memory.
//------------------------------------------------------------------------------

UndoAction::~UndoAction()
{
    // Note that we may leak memory if NotifyDispose returns anything other than
    // noErr. However, it is possible that the process allocating the memory for
    // the undo action no longer exists. That's why we are trying to avoid allocation.

    if (NotifyDispose(this) != procNotFound)
    {
        TRY
            if (fUndoActionLabel)
                DisposeIText(fUndoActionLabel);
            if (fRedoActionLabel)
                DisposeIText(fRedoActionLabel);
            if (fActionData)
                DisposeByteArray(fActionData);
        CATCH_ALL
            WARN("Error %ld encountered deleting an undo action.", ErrorCode());
        ENDTRY
    }
}

//------------------------------------------------------------------------------

class SystemUndo
{
  public:
        void operator delete(void* ptr) {DisposePtr((Ptr)ptr);}
    SystemUndo();
    ~SystemUndo();
    void    Initialize();

    ODSize        Purge(ODSize size);
    ODBoolean    CheckActionOK(UndoAction* action);
    void        AddActionToHistory(ODPart* whichPart,
                                    ODActionData* actionData,
                                    ODActionType actionType,
                                    ODName* undoActionLabel,
                                    ODName* redoActionLabel);
    void    Undo();
    void    Redo();
    void    MarkActionHistory();
    void    ClearActionHistory(ODRespectMarksChoices respectMarks);
    void    ClearRedoHistory();
    ODBoolean    PeekUndoHistory(ODPart** part,
                                ODActionData* actionData,
                                ODActionType* actionType,
                                ODName* actionLabel);
    ODBoolean    PeekRedoHistory(ODPart** part,
                                ODActionData* actionData,
                                ODActionType* actionType,
                                ODName* actionLabel);
    void        RemoveEntriesForThisProcess();
    void        AddClient(ODUndo* docUndoObject);
    void        RemoveClient(ODUndo* docUndoObject);
    ODULong        GetNumClients();
    void        AbortCurrentTransaction();
  private:
    void        TransactionUndo(UndoAction* firstAction);
    void        TransactionRedo(UndoAction* firstAction);
    void        MarkActionOrSelf(UndoAction* action, ODBoolean* mark);
    void        ClearActionsToMark(UndoOrderedCollection* stack);
    void        ClearStack(UndoOrderedCollection* stack);
    ODBoolean    PeekHistory(ODPart** part,
                                ODActionData* actionData,
                                ODActionType* actionType,
                                ODName* actionLabel,
                                ODUndoRedoType which);
    void        MoveUndoToRedo();
    void        MoveRedoToUndo();
    ODBoolean     ShouldStackBeCleared(UndoOrderedCollection* stack);

    UndoOrderedCollection*        fUndoStack;
    UndoOrderedCollection*        fRedoStack;
    ODULong                        fInTransaction;
    ODBoolean                fCurrentlyUndoingOrRedoing;
    ODULong                fNumUsers;
};

//------------------------------------------------------------------------------
// SystemUndo::SystemUndo
//------------------------------------------------------------------------------

SystemUndo::SystemUndo()
{
    fUndoStack = kODNULL;
    fRedoStack = kODNULL;
    fInTransaction = 0;
    fCurrentlyUndoingOrRedoing = kODFalse;
    fNumUsers = 0;
}

//------------------------------------------------------------------------------
// SystemUndo::Initialize
//------------------------------------------------------------------------------

void SystemUndo::Initialize ()
{
    ODUndoMemoryAllocation    heap = kODSystemHeap;

    fUndoStack = new (heap) UndoOrderedCollection(heap);
    fRedoStack = new (heap) UndoOrderedCollection(heap);

}

//------------------------------------------------------------------------------
// SystemUndo::~SystemUndo
//------------------------------------------------------------------------------

SystemUndo::~SystemUndo()
{
//    WASSERTM(0, "System Undo object being destroyed!");
    delete fUndoStack;
    delete fRedoStack;
}

//------------------------------------------------------------------------------
// SystemUndo::Purge
//------------------------------------------------------------------------------

ODSize    SystemUndo::Purge(ODSize size)
{
    ODUnused(size);
    return 0;
}

//------------------------------------------------------------------------------
// SystemUndo::CheckActionOK
//------------------------------------------------------------------------------

ODBoolean SystemUndo::CheckActionOK(UndoAction* action)
{
    if (action && !(action->fMark))
        return kODTrue;
    return kODFalse;
}

//------------------------------------------------------------------------------
// SystemUndo::AddClient
//------------------------------------------------------------------------------

void SystemUndo::AddClient(ODUndo* docUndoObject)
{
    ODUnused(docUndoObject);
    ++fNumUsers;
}

//------------------------------------------------------------------------------
// SystemUndo::RemoveClient
//------------------------------------------------------------------------------

void SystemUndo::RemoveClient(ODUndo* docUndoObject)
{
    ODUnused(docUndoObject);
    --fNumUsers;
}

//------------------------------------------------------------------------------
// SystemUndo::GetNumClients
//------------------------------------------------------------------------------

ODULong SystemUndo::GetNumClients()
{
    return fNumUsers;
}

//------------------------------------------------------------------------------
// SystemUndo::AddActionToHistory
//------------------------------------------------------------------------------

void SystemUndo::AddActionToHistory(ODPart* whichPart,
                                    ODActionData* actionData,
                                    ODActionType actionType,
                                    ODName* undoActionLabel,
                                    ODName* redoActionLabel)
{
    if (fCurrentlyUndoingOrRedoing)
        THROW(kODErrCannotAddAction);

//    if (fInTransaction && actionType == kODBeginAction)
//        THROW(kODErrCannotAddAction);

    if (actionType == kODBeginAction)
        ++fInTransaction;
    if (actionType == kODEndAction)
        --fInTransaction;

    // NOT DOING THESE ALLOCATIONS IN THE SYSTEM HEAP!
//    if (undoActionLabel)
        ODIText* undoName = CopyIText(undoActionLabel);
//    if (redoActionLabel)
        ODIText* redoName = CopyIText(redoActionLabel);

//    if (actionData)
        ODActionData* copiedData = CopyByteArray(actionData);

    UndoAction* action =
                    new (kODSystemHeap) UndoAction(whichPart, copiedData,
                                                    actionType, undoName,
                                                    redoName);
    fUndoStack->AddFirst(action);
    this->ClearStack(fRedoStack);
}

//------------------------------------------------------------------------------
// SystemUndo::MoveUndoToRedo
//
//    Utility to move item from top of one stack to the top of another.
//------------------------------------------------------------------------------

void SystemUndo::MoveUndoToRedo()
{
    ElementType item = fUndoStack->RemoveFirst();
    ((UndoAction*)item)->fDoneState = kODUndone;
    fRedoStack->AddFirst(item);
}

//------------------------------------------------------------------------------
// SystemUndo::MoveRedoToUndo
//
//    Utility to move item from top of one stack to the top of another.
//------------------------------------------------------------------------------

void SystemUndo::MoveRedoToUndo()
{
    ElementType item = fRedoStack->RemoveFirst();
    ((UndoAction*)item)->fDoneState = kODRedone;
    fUndoStack->AddFirst(item);
}

//------------------------------------------------------------------------------
// SystemUndo::Undo
//
//    If there's an error while undoing anything, just clear the stacks and get
//    out.
//------------------------------------------------------------------------------

void SystemUndo::Undo()
{
    UndoAction* action = (UndoAction*)fUndoStack->First();
    if (!this->CheckActionOK(action))
        THROW(kODErrEmptyStack);

    fCurrentlyUndoingOrRedoing = kODTrue;

    TRY
        if (action->fActionType == kODEndAction) // End is at top for an Undo
            this->TransactionUndo(action);
        else
        {
            THROW_IF_ERROR(NotifyUndo(action, kODBringToFront));
            this->MoveUndoToRedo();
        }
    CATCH_ALL
        this->ClearActionHistory(kODDontRespectMarks);
        fCurrentlyUndoingOrRedoing = kODFalse;
        RERAISE;
    ENDTRY
    fCurrentlyUndoingOrRedoing = kODFalse;
}

//------------------------------------------------------------------------------
// SystemUndo::ShouldStackBeCleared
//------------------------------------------------------------------------------

ODBoolean SystemUndo::ShouldStackBeCleared(UndoOrderedCollection* stack)
{
    UndoOrderedCollectionIterator iter(stack);
    UndoAction* action = (UndoAction*) iter.First();
    ODULong        nestedTransactionCounter = 0;

    if (action)
    {
        do
        {
            if (IsValidProcess(&action->fProcessNum))
            {
                if (action->fActionType == kODBeginAction)
                    --nestedTransactionCounter;
                else if (action->fActionType == kODEndAction)
                    ++nestedTransactionCounter;
            }
            else
                return kODTrue;
            action = (UndoAction*)iter.Next();
        }
        while ((nestedTransactionCounter) && action);
    }

    if (nestedTransactionCounter)
        return kODTrue;

    return kODFalse;
}

//------------------------------------------------------------------------------
// SystemUndo::TransactionUndo
//------------------------------------------------------------------------------

void SystemUndo::TransactionUndo(UndoAction* firstAction)
{
    UndoAction*    action;
    ODULong        nestedTransactionCounter = 1;

    THROW_IF_ERROR(NotifyUndo(firstAction, ! kODBringToFront));
    this->MoveUndoToRedo();

    do
    {
        action = (UndoAction*)fUndoStack->First();
        if (action == (UndoAction*)kODNULL)
            THROW(kODErrNoBeginAction);
        THROW_IF_ERROR(NotifyUndo(action, ! kODBringToFront));
        this->MoveUndoToRedo();
        if (action->fActionType == kODBeginAction)
            --nestedTransactionCounter;
        else if (action->fActionType == kODEndAction)
            ++nestedTransactionCounter;
    }
    while (nestedTransactionCounter);
}

//------------------------------------------------------------------------------
// SystemUndo::Redo
//------------------------------------------------------------------------------

void SystemUndo::Redo()
{
    UndoAction* action = (UndoAction*)fRedoStack->First();
    if (!this->CheckActionOK(action))
        THROW(kODErrEmptyStack);

    fCurrentlyUndoingOrRedoing = kODTrue;

    TRY
        if (action->fActionType == kODBeginAction)//Start is at top for an Redo
            this->TransactionRedo(action);
        else
        {
            THROW_IF_ERROR(NotifyRedo(action, kODBringToFront));
            this->MoveRedoToUndo();
        }
    CATCH_ALL
        this->ClearActionHistory(kODDontRespectMarks);
        fCurrentlyUndoingOrRedoing = kODFalse;
        RERAISE;
    ENDTRY
    fCurrentlyUndoingOrRedoing = kODFalse;
}

//------------------------------------------------------------------------------
// SystemUndo::TransactionRedo
//------------------------------------------------------------------------------

void SystemUndo::TransactionRedo(UndoAction* firstAction)
{
    UndoAction*    action;
    ODULong        nestedTransactionCounter = 1;

    THROW_IF_ERROR(NotifyRedo(firstAction, ! kODBringToFront));
    this->MoveRedoToUndo();

    do
    {
        action = (UndoAction*)fRedoStack->First();
//        if (action == (UndoAction*)kODNULL)
//            THROW(kODErrNoBeginAction);
        THROW_IF_ERROR(NotifyRedo(action, ! kODBringToFront));
        this->MoveRedoToUndo();
        if (action->fActionType == kODBeginAction)
            ++nestedTransactionCounter;
        else if (action->fActionType == kODEndAction)
            --nestedTransactionCounter;
    }
    while (nestedTransactionCounter);
}

//------------------------------------------------------------------------------
// SystemUndo::MarkActionHistory
//------------------------------------------------------------------------------

void SystemUndo::MarkActionHistory()
{
    UndoAction*    action;

    action = (UndoAction*)fUndoStack->First();
    if (action)
        action->fMark = kODTrue;
    action = (UndoAction*)fRedoStack->First();
    if (action)
        action->fMark = kODTrue;
}

//------------------------------------------------------------------------------
// SystemUndo::ClearStack
//------------------------------------------------------------------------------

void SystemUndo::ClearStack(UndoOrderedCollection* stack)
{
    UndoOrderedCollectionIterator    iter(stack);
    UndoAction*            action;

    for (action = (UndoAction*)iter.First();
            iter.IsNotComplete();
            action = (UndoAction*)iter.Next())
    {
        delete action;
    }

    stack->RemoveAll();
}

//------------------------------------------------------------------------------
// SystemUndo::ClearActionsToMark
//
//    To make more efficient, should just start removing items from the front of
//    the list til I hit the mark.
//------------------------------------------------------------------------------

void SystemUndo::ClearActionsToMark(UndoOrderedCollection* stack)
{
    UndoOrderedCollectionIterator    collectionIter(stack);
    UndoAction*                    action;
    UndoOrderedCollection            elementsToDelete;

    // ADD ELEMENTS TO REMOVE TO A LIST
    for (action = (UndoAction*)collectionIter.First();
            collectionIter.IsNotComplete();
            action = (UndoAction*)collectionIter.Next())
    {
        if (action->fMark != kODFalse)
        {
            action->fMark = kODFalse;
            break;
        }
        else
            elementsToDelete.AddFirst(action);
    }

    // REMOVE ELEMENTS
    UndoOrderedCollectionIterator    deleteIter(&elementsToDelete);
    for (action = (UndoAction*)deleteIter.First();
            deleteIter.IsNotComplete();
            action = (UndoAction*)deleteIter.Next())
    {
        stack->Remove(action);
        delete action;
    }
}

//------------------------------------------------------------------------------
// SystemUndo::ClearActionHistory
//------------------------------------------------------------------------------

void SystemUndo::ClearActionHistory(ODRespectMarksChoices respectMarks)
{
    if (respectMarks == kODRespectMarks)
    {
        this->ClearActionsToMark(fUndoStack);
        this->ClearActionsToMark(fRedoStack);
    }
    else
    {
        this->ClearStack(fUndoStack);
        this->ClearStack(fRedoStack);
    }
}

//------------------------------------------------------------------------------
// SystemUndo::ClearRedoHistory
//------------------------------------------------------------------------------

void SystemUndo::ClearRedoHistory()
{
    this->ClearActionsToMark(fRedoStack);
}

//------------------------------------------------------------------------------
// SystemUndo::AbortCurrentTransaction
//------------------------------------------------------------------------------

void SystemUndo::AbortCurrentTransaction()
{
    ODULong            nestingLevel = 0;
    ODActionType    actionType;

    if (fCurrentlyUndoingOrRedoing)
        return;
    if (!fInTransaction)
        return;

    UndoAction* action = (UndoAction*)fUndoStack->First();

    do
    {
        if (action->fActionType == kODEndAction)
            ++nestingLevel;
        fUndoStack->RemoveFirst();
        actionType = action->fActionType;
        THROW_IF_ERROR(NotifyUndo(action,  ! kODBringToFront));
        delete action;
        if (actionType == kODBeginAction && nestingLevel == 0)
            break;
        action = (UndoAction*)fUndoStack->First();//should never be NULL, right?
    }
    while (kODTrue);
}

//------------------------------------------------------------------------------
// SystemUndo::PeekUndoHistory
//------------------------------------------------------------------------------

ODBoolean SystemUndo::PeekUndoHistory(ODPart** part,
                                ODActionData* actionData,
                                ODActionType* actionType,
                                ODName* actionLabel)
{
    return PeekHistory(part, actionData, actionType, actionLabel, kUndo);
}

//------------------------------------------------------------------------------
// SystemUndo::PeekRedoHistory
//------------------------------------------------------------------------------

ODBoolean SystemUndo::PeekRedoHistory(ODPart** part,
                                ODActionData* actionData,
                                ODActionType* actionType,
                                ODName* actionLabel)
{
    return PeekHistory(part, actionData, actionType, actionLabel, kRedo);
}

//------------------------------------------------------------------------------
// SystemUndo::PeekHistory
//
//    We could choose to only fill out the pieces needed here.
//------------------------------------------------------------------------------

ODBoolean SystemUndo::PeekHistory(ODPart** part,
                                ODActionData* actionData,
                                ODActionType* actionType,
                                ODName* actionLabel,
                                ODUndoRedoType which)
{
    UndoOrderedCollection*    stack;
    ODIText*                iText;
    ODBoolean                createPhonyIText = kODFalse;

    if (which == kUndo)
        stack = fUndoStack;
    else if (which == kRedo)
        stack = fRedoStack;

    UndoAction*    action = (UndoAction*)stack->First();

    if (!this->CheckActionOK(action))
        return kODFalse;
    else
    {
        if (action->fMark != kODFalse)
            return kODFalse;
        // We need to see whether the action is still valid
        // (i.e., whether the process is still up and running).
        else if (this->ShouldStackBeCleared(stack))
        {
            this->ClearActionHistory(kODDontRespectMarks);
            return kODFalse;
        }
        else
        {
            *part = action->fPart;
            *actionType = action->fActionType;

            // NP: null data mods
            if (action->fActionData)
                *actionData = CopyByteArrayStruct(action->fActionData);
            else
                *actionData = CreateEmptyByteArrayStruct(0);

            if (which == kUndo)
            {
                if (action->fUndoActionLabel)
                    iText = action->fUndoActionLabel;
                else
                    // NP: null data mods
                    createPhonyIText = kODTrue;
            }
            else if (which == kRedo)
            {
                if (action->fRedoActionLabel)
                    iText = action->fRedoActionLabel;
                else
                    // NP: null data mods
                    createPhonyIText = kODTrue;
            }

            if (createPhonyIText)
            {
                // NP: null data mods
                ODIText*    emptyIText = CreateIText(0);
                *actionLabel = CopyITextStruct(emptyIText);
                DisposeIText(emptyIText);
            }
            else
                *actionLabel = CopyITextStruct(iText);

            return kODTrue;
        }
    }
}

//------------------------------------------------------------------------------
// NotifyUndoOrRedoOrDispose
//
//    Notify part to Undo or Redo or Dispose its data.
//    Could fine-tune to only pack parameters needed according to "which"
//    parameter
//------------------------------------------------------------------------------

static OSErr NotifyUndoOrRedoOrDispose(UndoAction* action,
                                                ODUndoRedoType which,
                                                ODBoolean    bringToFront)
{
    AEAddressDesc        address;
    AppleEvent            message;
    AppleEvent            reply = NULL_DESCRIPTOR_DEFINITION;
    OSErr                error = noErr;
    ProcessSerialNumber    psn;
    Boolean                isSameProcess;
    DescType            eventID;
//    ProcessInfoRec        processRec;
    octet                validAddrForPhonyData;

    TRY
#if 0
        // MAKE SURE PROCESS IS STILL VALID. USE SIDE EFFECT OF ERROR RETURN
        //    FROM GetProcessInformation.
        processRec.processInfoLength = sizeof(ProcessInfoRec);
        processRec.processName = kODNULL;
        processRec.processAppSpec = kODNULL;
        THROW_IF_ERROR(GetProcessInformation(&action->fProcessNum, &processRec));
#endif /* 0 */
        // SOME CODE TO HANDLE THE SEND TO SELF CASE WELL. IF WE HAVE A STANDARD
        //    IDLE PROC TO USE, WE PROBABLY DON'T NEED THIS. (NP-WHAT DID I MEAN
        //    HERE?)
        THROW_IF_ERROR(GetCurrentProcess(&psn));
        THROW_IF_ERROR(SameProcess(&action->fProcessNum, &psn,
                                    &isSameProcess));
        if (isSameProcess)
        {
            psn.lowLongOfPSN = kCurrentProcess;
            psn.highLongOfPSN = 0;
        }
        else
            psn = action->fProcessNum;
#if 0
        {
            // MAKE SURE PROCESS IS STILL ALIVE.
            ODBoolean    processStillExists = kODFalse;

            while (kODTrue)
            {
                if (GetNextProcess(&psn) != noErr)
                    break;
                THROW_IF_ERROR(SameProcess(&action->fProcessNum, &psn,
                                            &isSameProcess));
                if (isSameProcess)
                {
                    processStillExists = kODTrue;
                    break;
                }
            }

            if (!processStillExists)
                THROW(procNotFound);
        }
#endif /* 0 */
        THROW_IF_ERROR(AECreateDesc(typeProcessSerialNumber,
                                    (Ptr)&psn, sizeof(psn), &address));

        TempAEDesc tempAddress(&address);
        if (which == kUndo)
            eventID = kUndoNotifyID;
        else if (which == kRedo)
            eventID = kRedoNotifyID;
        else if (which == kDispose)
            eventID = kDisposeActionNotifyID;

        THROW_IF_ERROR(AECreateAppleEvent(kODShellSignature, eventID,
                        &address, kAutoGenerateReturnID, kAnyTransactionID,
                        &message));
        TempAEDesc tempMessage(&message); // DMc make sure it is disposed

        // NP: null data mods
        if (!action->fActionData)
        {
            action->fActionData->_length = 0;
            action->fActionData->_buffer = &validAddrForPhonyData;
        }
        THROW_IF_ERROR(AEPutParamPtr(&message, kDataPtrKeyword, typeChar,
                                    action->fActionData->_buffer,
                                    action->fActionData->_length));

        THROW_IF_ERROR(AEPutParamPtr(&message, kPartPtrKeyword, typeInteger,
                                    (Ptr)&action->fPart,
                                    sizeof(action->fPart)));

        THROW_IF_ERROR(AEPutParamPtr(&message, kDoneStateKeyword, typeInteger,
                                    (Ptr)&action->fDoneState,
                                    sizeof(action->fDoneState)));

        if (bringToFront)
            SetFrontProcess(&psn);

        THROW_IF_ERROR(AESend(&message, &reply,
                                (which == kDispose ? kAENoReply : kAEWaitReply)
                                    + kAECanInteract + kAECanSwitchLayer + kAEDontRecord,
                                kAENormalPriority,
                                kAEDefaultTimeout,
                                (AEIdleUPP)kODNULL, (AEFilterUPP)kODNULL));

        AEDisposeDesc(&reply); // DMc
    CATCH_ALL
        error = ErrorCode();
    ENDTRY

    return error;
}

//------------------------------------------------------------------------------
// NotifyUndo
//
//    Call ODPart::Undo.
//------------------------------------------------------------------------------

static OSErr NotifyUndo(UndoAction* action, ODBoolean bringToFront)
{
    return NotifyUndoOrRedoOrDispose(action, kUndo, bringToFront);
}

//------------------------------------------------------------------------------
// NotifyRedo
//
//    Call ODPart::Redo.
//------------------------------------------------------------------------------

static OSErr NotifyRedo(UndoAction* action, ODBoolean bringToFront)
{
    return NotifyUndoOrRedoOrDispose(action, kRedo, bringToFront);
}

//------------------------------------------------------------------------------
// NotifyDispose
//
//    Call ODPart::DiposeActionState.
//------------------------------------------------------------------------------

static OSErr NotifyDispose(UndoAction* action)
{
    return NotifyUndoOrRedoOrDispose(action, kDispose, ! kODBringToFront);
}

//==============================================================================
// ODUndo
//==============================================================================

//------------------------------------------------------------------------------
// HandleUndoOrRedoOrDisposeNotify
//
//    Could fine-tune to only unpack parameters needed according to "which"
//    parameter
//------------------------------------------------------------------------------

static OSErr HandleUndoOrRedoOrDisposeNotify(AppleEvent* message,
                                                AppleEvent* reply,
                                                long refCon,
                                                ODUndoRedoType which)
{
    ODUnused(reply);
    ODUnused(refCon);

    OSErr            error = noErr;
    DescType        gotType;
//    ODActionData*    data;
    ODPart*            part;
    ODDoneState        doneState;
    Size            actualSize;
//    Size            maximumDataSize;
    Size            maximumPartSize = sizeof(part);
    Size            maximumDoneStateSize = sizeof(doneState);

    TRY
#if 0
        gotType = typeChar;
        THROW_IF_ERROR(AESizeOfParam(message, kDataPtrKeyword, &gotType,
                                        &actualSize));
        if (gotType != typeChar)
            THROW(errAECorruptData);
        maximumDataSize = actualSize;
        data = CreateEmptyByteArray(actualSize);
        THROW_IF_ERROR(AEGetParamPtr(message, kDataPtrKeyword, typeChar,
                                        &gotType, data->_buffer, maximumDataSize,
                                        &actualSize));
        if (actualSize != maximumDataSize)
            THROW(errAECorruptData);
#endif /* 0 */
        TempODByteArray data = ODAEGetByteArray(message, kDataPtrKeyword,
                                                typeChar);

        THROW_IF_ERROR(AEGetParamPtr(message, kPartPtrKeyword, typeInteger,
                                    &gotType, (Ptr)&part, maximumPartSize,
                                    &actualSize));
        if (gotType != typeInteger || actualSize != maximumPartSize)
            THROW(errAECorruptData);

        THROW_IF_ERROR(AEGetParamPtr(message, kDoneStateKeyword, typeInteger,
                                    &gotType, (Ptr)&doneState,
                                    maximumDoneStateSize,
                                    &actualSize));
        if (gotType != typeInteger || actualSize != maximumDoneStateSize)
            THROW(errAECorruptData);

        Environment*    ev = somGetGlobalEnvironment();
        if (which == kUndo)
        {
            part->UndoAction(ev, data);
            error = ODGetSOMException(ev);
        }
        else if (which == kRedo)
        {
            part->RedoAction(ev, data);
            error = ODGetSOMException(ev);
        }
        else if (which == kDispose)
        {
            part->DisposeActionState(ev, data, doneState);
            error = ODGetSOMException(ev);
        }

//        DisposeByteArray(data);

    CATCH_ALL
        error = ErrorCode();
    ENDTRY

    return error;
}

//------------------------------------------------------------------------------
// HandleUndoNotify
//------------------------------------------------------------------------------

static pascal OSErr HandleUndoNotify(AppleEvent* message, AppleEvent* reply,
                                        long refCon)
{
    return HandleUndoOrRedoOrDisposeNotify(message, reply, refCon, kUndo);
}

//------------------------------------------------------------------------------
// HandleRedoNotify
//------------------------------------------------------------------------------

static pascal OSErr HandleRedoNotify(AppleEvent* message, AppleEvent* reply,
                                        long refCon)
{
    return HandleUndoOrRedoOrDisposeNotify(message, reply, refCon, kRedo);
}

//------------------------------------------------------------------------------
// HandleDisposeNotify
//------------------------------------------------------------------------------

static pascal OSErr HandleDisposeNotify(AppleEvent* message, AppleEvent* reply,
                                        long refCon)
{
    return HandleUndoOrRedoOrDisposeNotify(message, reply, refCon, kDispose);
}

//------------------------------------------------------------------------------
// ODUndo::InitUndo
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoInitUndo(ODUndo *somSelf, Environment *ev)
{
    ODUndoData *somThis = ODUndoGetData(somSelf);
    ODUndoMethodDebug("ODUndo","ODUndoInitUndo");

    /* Moved from somInit. SOM itself sets fields to zero
    _fSystemUndo = kODNULL;
    */

    TRY
        somSelf->InitObject(ev);

        _fSystemUndo = GetSystemUndo();
        if (!_fSystemUndo)
        {
            _fSystemUndo = new (kODSystemHeap) SystemUndo();
            if (_fSystemUndo)
            {
                _fSystemUndo->Initialize();
                SetSystemUndo(_fSystemUndo);
            }
        }
        THROW_IF_ERROR(AEInstallEventHandler(kODShellSignature,
                                    kUndoNotifyID,
                                    NewAEEventHandlerProc(HandleUndoNotify),
                                    (long)somSelf, !kIsSysHandler));
        THROW_IF_ERROR(AEInstallEventHandler(kODShellSignature,
                                    kRedoNotifyID,
                                    NewAEEventHandlerProc(HandleRedoNotify),
                                    (long)somSelf, !kIsSysHandler));
        THROW_IF_ERROR(AEInstallEventHandler(kODShellSignature,
                                    kDisposeActionNotifyID,
                                    NewAEEventHandlerProc(HandleDisposeNotify),
                                    (long)somSelf, !kIsSysHandler));
        _fSystemUndo->AddClient(somSelf);
    CATCH_ALL
        ODDeleteObject(_fSystemUndo);
        ODSetSOMException(ev, ErrorCode());
    ENDTRY
}

//------------------------------------------------------------------------------
// ODUndo::~ODUndo
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndosomUninit(ODUndo *somSelf)
{
    ODUndoData *somThis = ODUndoGetData(somSelf);
    ODUndoMethodDebug("ODUndo","ODUndosomUninit");

    if (_fSystemUndo)
    {
        _fSystemUndo->RemoveClient(somSelf);

        if (_fSystemUndo->GetNumClients() == 0) // reclaim space.
        {
    //        WARN("Deleting system undo object.");
            ODDeleteObject(_fSystemUndo);
            SetSystemUndo(kODNULL);
        }
    }
    ODUndo_parents_somUninit(somSelf);
}
#if 0
//------------------------------------------------------------------------------
// ODUndo::Purge
//------------------------------------------------------------------------------

SOM_Scope ODSize  SOMLINK ODUndoPurge(ODUndo *somSelf, Environment *ev,
        ODSize size)
{
    ODUndoData *somThis = ODUndoGetData(somSelf);
    ODUndoMethodDebug("ODUndo","ODUndoPurge");

    ODSize purged = 0;
    ODVolatile(purged);

    SOM_TRY
        if (_fSystemUndo) {
            purged =  _fSystemUndo->Purge(size);
        }
        else
            purged =  0;

        purged += parent_Purge(somSelf,ev,size);
    SOM_CATCH_ALL
        WARN("Error %ld trying to purge in ODUndoPurge",ErrorCode());
        SetErrorCode(kODNoError);        // dh - Eat the exception; Purge should not
                                        // propagate it because clients function
                                        // fine whether memory was purged or not.
    SOM_ENDTRY

    return purged;
}
#endif /* 0 */
//------------------------------------------------------------------------------
// ODUndo::AddActionToHistory
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoAddActionToHistory(ODUndo *somSelf, Environment *ev,
        ODPart* whichPart,
        ODActionData* actionData,
        ODActionType actionType,
        ODName* undoActionLabel,
        ODName* redoActionLabel)
{
    ODUndoData *somThis = ODUndoGetData(somSelf);
    ODUndoMethodDebug("ODUndo","ODUndoAddActionToHistory");

    SOM_TRY

    if (_fSystemUndo)
        _fSystemUndo->AddActionToHistory(whichPart, actionData, actionType,
                                        undoActionLabel, redoActionLabel);
    else
        THROW(kODErrOutOfMemory);

    SOM_CATCH_ALL
    SOM_ENDTRY
}

//------------------------------------------------------------------------------
// ODUndo::Undo
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoUndo(ODUndo *somSelf, Environment *ev)
{
    ODUndoData *somThis = ODUndoGetData(somSelf);
    ODUndoMethodDebug("ODUndo","ODUndoUndo");

    SOM_TRY

    if (_fSystemUndo)
        _fSystemUndo->Undo();
    else
        THROW(kODErrEmptyStack);

    SOM_CATCH_ALL
    SOM_ENDTRY
}

//------------------------------------------------------------------------------
// ODUndo::Redo
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoRedo(ODUndo *somSelf, Environment *ev)
{
    ODUndoData *somThis = ODUndoGetData(somSelf);
    ODUndoMethodDebug("ODUndo","ODUndoRedo");

    SOM_TRY

    if (_fSystemUndo)
        _fSystemUndo->Redo();
    else
        THROW(kODErrEmptyStack);

    SOM_CATCH_ALL
    SOM_ENDTRY
}

//------------------------------------------------------------------------------
// ODUndo::MarkActionHistory
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoMarkActionHistory(ODUndo *somSelf, Environment *ev)
{
    ODUndoData *somThis = ODUndoGetData(somSelf);
    ODUndoMethodDebug("ODUndo","ODUndoMarkActionHistory");

    SOM_TRY

    if (_fSystemUndo)
        _fSystemUndo->MarkActionHistory();
    else
        THROW(kODErrCannotMarkAction);

    SOM_CATCH_ALL
    SOM_ENDTRY
}

//------------------------------------------------------------------------------
// ODUndo::ClearActionHistory
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoClearActionHistory(ODUndo *somSelf, Environment *ev,
        ODRespectMarksChoices respectMarks)
{
    ODUndoMethodDebug("ODUndo","ODUndoClearActionHistory");
    ODUndoData *somThis = ODUndoGetData(somSelf);

    SOM_TRY

    if (_fSystemUndo)
        _fSystemUndo->ClearActionHistory(respectMarks);

    SOM_CATCH_ALL
    SOM_ENDTRY
}

//------------------------------------------------------------------------------
// ODUndo::ClearRedoHistory
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoClearRedoHistory(ODUndo *somSelf, Environment *ev)
{
    ODUndoMethodDebug("ODUndo","ODUndoClearRedoHistory");
    ODUndoData *somThis = ODUndoGetData(somSelf);

    SOM_TRY

    if (_fSystemUndo)
        _fSystemUndo->ClearRedoHistory();

    SOM_CATCH_ALL
    SOM_ENDTRY
}

//------------------------------------------------------------------------------
// ODUndo::PeekUndoHistory
//------------------------------------------------------------------------------

SOM_Scope ODBoolean  SOMLINK ODUndoPeekUndoHistory(ODUndo *somSelf, Environment *ev,
        ODPart** part,
        ODActionData* actionData,
        ODActionType* actionType,
        ODName* actionLabel)
{
    ODUndoMethodDebug("ODUndo","ODUndoPeekUndoHistory");
    ODUndoData *somThis = ODUndoGetData(somSelf);

    SOM_TRY

    if (_fSystemUndo)
        return _fSystemUndo->PeekUndoHistory(part, actionData, actionType,
                                                actionLabel);
    else
        return kODFalse;

    SOM_CATCH_ALL
    SOM_ENDTRY
    return kODFalse;
}

//------------------------------------------------------------------------------
// ODUndo::PeekRedoHistory
//------------------------------------------------------------------------------

SOM_Scope ODBoolean  SOMLINK ODUndoPeekRedoHistory(ODUndo *somSelf, Environment *ev,
        ODPart** part,
        ODActionData* actionData,
        ODActionType* actionType,
        ODName* actionLabel)
{
    ODUndoMethodDebug("ODUndo","ODUndoPeekRedoHistory");
    ODUndoData *somThis = ODUndoGetData(somSelf);

    SOM_TRY

    if (_fSystemUndo)
        return _fSystemUndo->PeekRedoHistory(part, actionData, actionType,
                                                actionLabel);
    else
        return kODFalse;

    SOM_CATCH_ALL
    SOM_ENDTRY
    return kODFalse;
}

//------------------------------------------------------------------------------
// ODUndo::AbortCurrentTransaction
//------------------------------------------------------------------------------

SOM_Scope void  SOMLINK ODUndoAbortCurrentTransaction(ODUndo *somSelf, Environment *ev)
{
    ODUndoMethodDebug("ODUndo","ODUndoAbortCurrentTransaction");
    ODUndoData *somThis = ODUndoGetData(somSelf);

    SOM_TRY

    if (_fSystemUndo)
        _fSystemUndo->AbortCurrentTransaction();

    SOM_CATCH_ALL
    SOM_ENDTRY
}