Undo-Redo feature in Fabric.js

Question

Is there any built-in support for for undo/redo in Fabric.js? Can you please guide me on how you used this cancel and repeat in [http://printio.ru/][1]

Answer 1

I know its late to answer this but this is my version of implementing this. Can be useful to someone.

I have implemented this feature by saving Canvas States as JSON. Whenever a user adds or modifies an object in the Canvas, it will save the changed canvas state and maintain it in an array. This array is then manipulated whenever user clicks on Undo or Redo button.

Take a look at this link. I have also provided a working Demo URL.

https://github.com/abhi06991/Undo-Redo-Fabricjs

HTML:

 
Undo
Redo

JS:

var canvasDemo = (function(){
  var _canvasObject = new fabric.Canvas('canvas',{backgroundColor : "#f5deb3"});
    var _config = {
        canvasState             : [],
        currentStateIndex       : -1,
        undoStatus              : false,
        redoStatus              : false,
        undoFinishedStatus      : 1,
        redoFinishedStatus      : 1,
    undoButton              : document.getElementById('undo'),
        redoButton              : document.getElementById('redo'),
    };
    _canvasObject.on(
        'object:modified', function(){
            updateCanvasState();
        }
    );

  _canvasObject.on(
        'object:added', function(){
            updateCanvasState();
        }
    );

  var addObject = function(){
     var rect = new fabric.Rect({
            left   : 100,
            top    : 100,
            fill   : 'red',
            width  : 200,
            height : 200
    });
        _canvasObject.add(rect);
        _canvasObject.setActiveObject(rect);
    _canvasObject.renderAll();
  }

    var updateCanvasState = function() {
        if((_config.undoStatus == false && _config.redoStatus == false)){
            var jsonData        = _canvasObject.toJSON();
            var canvasAsJson        = JSON.stringify(jsonData);
            if(_config.currentStateIndex < _config.canvasState.length-1){
                var indexToBeInserted                  = _config.currentStateIndex+1;
                _config.canvasState[indexToBeInserted] = canvasAsJson;
                var numberOfElementsToRetain           = indexToBeInserted+1;
                _config.canvasState                    = _config.canvasState.splice(0,numberOfElementsToRetain);
            }else{
            _config.canvasState.push(canvasAsJson);
            }
        _config.currentStateIndex = _config.canvasState.length-1;
      if((_config.currentStateIndex == _config.canvasState.length-1) && _config.currentStateIndex != -1){
        _config.redoButton.disabled= "disabled";
      }
        }
    }


    var undo = function() {
        if(_config.undoFinishedStatus){
            if(_config.currentStateIndex == -1){
            _config.undoStatus = false;
            }
            else{
            if (_config.canvasState.length >= 1) {
            _config.undoFinishedStatus = 0;
              if(_config.currentStateIndex != 0){
                    _config.undoStatus = true;
                  _canvasObject.loadFromJSON(_config.canvasState[_config.currentStateIndex-1],function(){
                                var jsonData = JSON.parse(_config.canvasState[_config.currentStateIndex-1]);
                            _canvasObject.renderAll();
                        _config.undoStatus = false;
                        _config.currentStateIndex -= 1;
                                _config.undoButton.removeAttribute("disabled");
                                if(_config.currentStateIndex !== _config.canvasState.length-1){
                                    _config.redoButton.removeAttribute('disabled');
                                }
                            _config.undoFinishedStatus = 1;
                });
              }
              else if(_config.currentStateIndex == 0){
                _canvasObject.clear();
                        _config.undoFinishedStatus = 1;
                        _config.undoButton.disabled= "disabled";
                        _config.redoButton.removeAttribute('disabled');
                _config.currentStateIndex -= 1;
              }
            }
            }
        }
    }

    var redo = function() {
        if(_config.redoFinishedStatus){
            if((_config.currentStateIndex == _config.canvasState.length-1) && _config.currentStateIndex != -1){
                _config.redoButton.disabled= "disabled";
            }else{
            if (_config.canvasState.length > _config.currentStateIndex && _config.canvasState.length != 0){
                    _config.redoFinishedStatus = 0;
                _config.redoStatus = true;
              _canvasObject.loadFromJSON(_config.canvasState[_config.currentStateIndex+1],function(){
                            var jsonData = JSON.parse(_config.canvasState[_config.currentStateIndex+1]);
                        _canvasObject.renderAll();
                        _config.redoStatus = false;
                    _config.currentStateIndex += 1;
                            if(_config.currentStateIndex != -1){
                                _config.undoButton.removeAttribute('disabled');
                            }
                        _config.redoFinishedStatus = 1;
            if((_config.currentStateIndex == _config.canvasState.length-1) && _config.currentStateIndex != -1){
              _config.redoButton.disabled= "disabled";
            }
              });
            }
            }
        }
    }


    return {
        addObject  : addObject,
        undoButton : _config.undoButton,
        redoButton : _config.redoButton,
        undo       : undo,
        redo       : redo,
  }


  })();



  canvasDemo.undoButton.addEventListener('click',function(){
        canvasDemo.undo();
    });

    canvasDemo.redoButton.addEventListener('click',function(){
        canvasDemo.redo();
    });
  canvasDemo.addObject();