llundo.cpp

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#include "linden_common.h"
#include "llundo.h"


// TODO:
// implement doubly linked circular list for ring buffer
// this will allow us to easily change the size of an undo buffer on the fly

//-----------------------------------------------------------------------------
// LLUndoBuffer()
//-----------------------------------------------------------------------------
LLUndoBuffer::LLUndoBuffer( LLUndoAction (*create_func()), S32 initial_count )
{
        mNextAction = 0;
        mLastAction = 0;
        mFirstAction = 0;
        mOperationID = 0;

        mNumActions = initial_count;    

        mActions = new LLUndoAction *[initial_count];

        //initialize buffer with actions
        for (S32 i = 0; i < initial_count; i++)
        {
                mActions[i] = create_func();
                if (!mActions[i])
                {
                        llerrs << "Unable to create action for undo buffer" << llendl;
                }
        }
}

//-----------------------------------------------------------------------------
// ~LLUndoBuffer()
//-----------------------------------------------------------------------------
LLUndoBuffer::~LLUndoBuffer()
{
        for (S32 i = 0; i < mNumActions; i++)
        {
                delete mActions[i];
        }

        delete [] mActions;
}

//-----------------------------------------------------------------------------
// getNextAction()
//-----------------------------------------------------------------------------
LLUndoBuffer::LLUndoAction* LLUndoBuffer::getNextAction(BOOL setClusterBegin)
{
        LLUndoAction *nextAction = mActions[mNextAction];

        if (setClusterBegin)
        {
                mOperationID++;
        }
        mActions[mNextAction]->mClusterID = mOperationID;

        mNextAction = (mNextAction + 1) % mNumActions;
        mLastAction = mNextAction;

        if (mNextAction == mFirstAction)
        {
                mActions[mFirstAction]->cleanup();
                mFirstAction = (mFirstAction + 1) % mNumActions;
        }

        return nextAction;
}

//-----------------------------------------------------------------------------
// undoAction()
//-----------------------------------------------------------------------------
BOOL LLUndoBuffer::undoAction()
{
        if (!canUndo())
        {
                return FALSE;
        }

        S32 prevAction = (mNextAction + mNumActions - 1) % mNumActions;

        while(mActions[prevAction]->mClusterID == mOperationID)
        {
                // go ahead and decrement action index
                mNextAction = prevAction;

                // undo this action
                mActions[mNextAction]->undo();

                // we're at the first action, so we don't know if we've actually undid everything
                if (mNextAction == mFirstAction)
                {
                        mOperationID--;
                        return FALSE;
                }

                // do wrap-around of index, but avoid negative numbers for modulo operator
                prevAction = (mNextAction + mNumActions - 1) % mNumActions;
        }

        mOperationID--;

        return TRUE;
}

//-----------------------------------------------------------------------------
// redoAction()
//-----------------------------------------------------------------------------
BOOL LLUndoBuffer::redoAction()
{
        if (!canRedo())
        {
                return FALSE;
        }

        mOperationID++;

        while(mActions[mNextAction]->mClusterID == mOperationID)
        {
                if (mNextAction == mLastAction)
                {
                        return FALSE;
                }

                mActions[mNextAction]->redo();

                // do wrap-around of index
                mNextAction = (mNextAction + 1) % mNumActions;
        }

        return TRUE;
}

//-----------------------------------------------------------------------------
// flushActions()
//-----------------------------------------------------------------------------
void LLUndoBuffer::flushActions()
{
        for (S32 i = 0; i < mNumActions; i++)
        {
                mActions[i]->cleanup();
        }
        mNextAction = 0;
        mLastAction = 0;
        mFirstAction = 0;
        mOperationID = 0;
}

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