Sorry your browser is not supported!

/* ============================================================*
 * This API allows you to add undo and redo functionality      *
 * to any of your programs, such as a tile map/level editor    *
 * or any other program you would need such functionality for! *
 * ============================================================*/
 
// First let's create a couple of constants which will keep our lists a reasonable size
#Constant UNDO_MAX_SIZE = 29 // this number is really 30 because lists start at 0!
#Constant REDO_MAX_SIZE = 29 
 
// This UDT holds any data required and can be customized easily!
Type DataBlock
	// This tells the computer what the action taken was
	actionType as Integer
	actionName as String
	
	// For a tile map editor, use this to store tile properties
	tileName as String
	tileType as Integer
	tilePosX as Integer
	tilePosY as Integer
	
	// Anything else you need can be added very easily!
EndType

// Create two expandable lists (NOTE: They *must* be global in order to access them properly!) on the DataBlock UDT
Global UndoList as DataBlock[]
Global RedoList as DataBlock[]

// Now create our functions which add actions to the undo and redo lists
Function AddToUndoList(actionType as Integer, actionName as String)
	// First we'll check our list size. If it's long we'll delete the oldest element.
	If UndoList.length > UNDO_MAX_SIZE Then UndoList.remove(0)
	
	// Create a local variable also based on the DataBlock UDT
	Local Undo as DataBlock
	
	// Add the action type and name to the undo list
	Undo.actionType = actionType
	Undo.actionName = actionName
	UndoList.insert(Undo)
EndFunction

Function AddToRedoList()
	// First we'll check our list size. If it's long we'll delete the oldest element.
	If RedoList.length > REDO_MAX_SIZE Then RedoList.remove(0)
	
	// Create a local variable also based on the DataBlock UDT (same as before)
	Local Redo as DataBlock
	
	// Find the last action that was Undone to add to the RedoList
	index = UndoList.length
	
	// Add the action type and name to the redo list
	Redo.actionType = UndoList[index].actionType
	Redo.actionName = UndoList[index].actionName
	RedoList.insert(Redo)
EndFunction

/* This function is called each time a new action is performed
 * It checkes to see if the action being performed is happening while
 * any elements exist in the RedoList. If they do, they MUST be deleted, 
 * so that we don't get errors later on! */
Function CheckNewAction()
	// Check the length of the RedoList
	If RedoList.length > -1 Then RedoList.length = -1
EndFunction

/* These functions are what actually undo/redo any previous action. */
Function Undo()
	// First we must grab the very last action inserted into the UndoList
	index = UndoList.length
	lastAction = UndoList[index].actionType
	
	// Then we will use a Select statement to determine what to undo!
	Select lastAction
		Case 1:
		EndCase
		Case 2:
		EndCase
		Case 3:
		EndCase
	EndSelect
	
EndFunction

Function Redo()
	// First we must find the last action inserted into the RedoList
	index = RedoList.length
	lastAction = RedoList[index].actionType
	
	// Determine what action to redo!
	Select lastAction
		Case 1:
		EndCase
		Case 2:
		EndCase
		Case 3:
		EndCase
	EndSelect
EndFunction

Case 1:
    // A tile has been placed so undo that!
    UndoTileMovement(lastTilePlacedID)
EndCase