public UndoManager()
{
this.mStack = sEmptyStack;
this.mStackSize = 0;
this.mStackSizeLimit = -1;
this.mLastCmdIndex = -1;
this.mCheckpoint = null;
}
public UndoManager(int stackCapacity)
{
if (stackCapacity < 0)
{
throw new ArgumentOutOfRangeException("stackCapacity");
}
else if (stackCapacity == 0)
{
this.mStack = sEmptyStack;
}
else
{
this.mStack = new Command[stackCapacity];
}
this.mStackSize = 0;
this.mStackSizeLimit = -1;
this.mLastCmdIndex = -1;
this.mCheckpoint = null;
}
public virtual bool IsExtendable(Command possibleExtension)
{
return false;
}
public virtual void Extend(Command possibleExtension)
{
}
public bool Submit(Command command)
{
if (command == null)
{
throw new ArgumentNullException("command");
}
if (!command.Execute())
{
command.Dispose();
return false;
}
if (this.CommandExecuted != null)
{
this.CommandExecuted(this, command);
}
Command cmd;
if (this.mLastCmdIndex < this.mStackSize - 1)
{
int index = this.mLastCmdIndex + 1;
for (int i = index; i < this.mStackSize; i++)
{
this.mStack[i].Dispose();
}
Array.Clear(this.mStack, index, this.mStackSize - index);
this.mStackSize = index;
}
if (this.mLastCmdIndex >= 0)
{
cmd = this.mStack[this.mLastCmdIndex];
if (cmd.IsExtendable(command))
{
cmd.Extend(command);
command.Dispose();
return true;
}
}
if (this.mStackSizeLimit >= 0 &&
!command.GroupWithPreviousCommand)
{
int j, count = 0;
for (j = 0; j < this.mStackSize; j++)
{
cmd = this.mStack[j];
if (!cmd.GroupWithPreviousCommand)
{
count++;
}
}
int rCount = count - this.mStackSizeLimit + 1;
if (rCount > 0)
{
count = 0;
int last = 0;
for (j = 0; j < this.mStackSize; j++)
{
cmd = this.mStack[j];
if (!cmd.GroupWithPreviousCommand)
{
count++;
}
if (count <= rCount)
{
last++;
cmd.Dispose();
}
}
if (last > this.mStackSize)
{
last = this.mStackSize;
}
if (last > 0)
{
this.mStackSize -= last;
if (this.mStackSize > 0)
{
Array.Copy(this.mStack, last,
this.mStack, 0, this.mStackSize);
}
Array.Clear(this.mStack, this.mStackSize, last);
}
}
}
this.mLastCmdIndex = this.mStackSize;
if (this.mStackSize == this.mStack.Length)
{
if (this.mStackSize == 0)
{
this.mStack = new Command[4];
}
else
{
Command[] stack = new Command[2 * this.mStackSize];
Array.Copy(this.mStack, 0, stack, 0, this.mStackSize);
this.mStack = stack;
}
}
this.mStack[this.mStackSize++] = command;
if (this.CommandAddedToHistory != null)
{
this.CommandAddedToHistory(this, command);
}
return true;
}
public void SetCheckpoint()
{
if (this.mLastCmdIndex >= 0)
{
this.mCheckpoint = this.mStack[this.mLastCmdIndex];
}
else
{
this.mCheckpoint = null;
}
}
public void ClearCheckpoint()
{
this.mCheckpoint = null;
}
