How to create Undo-Redo in kineticjs?

Question

Is there any simple way how to create undo redo function in Kineticjs ? I have found a Undo Manager for HTML 5 in https://github.com/ArthurClemens/Javascri

Answer 1

i have written a class for the functionality: http://www.sebastianviereck.de/en/redo-undo-class-kinetic-js/

Answer 2

To solve event listeners problem, work on by making clones

$scope.makeHistory=function() { 
  $scope.historyStep++;
  if ($scope.historyStep < $scope.history.length) {
      $scope.history.length = $scope.historyStep;
  } 
  var layerC = $scope.topLayer.clone(); 
  $scope.history.push(layerC);   
};

 $scope.undoObject = function(){  
  if($scope.historyStep > 0) {
    $scope.historyStep--;
    $scope.topLayer.destroy(); 
    if($scope.historyStep==0){
      $scope.topLayerAdd(2); // will put empty layer
    }
    else{
      var layer = $scope.history[$scope.historyStep-1].clone();
      $scope.topLayerAdd(1,layer);
    } 
    $scope.topLayer.draw();
  } 
};

$scope.redoObject = function(){  
  if($scope.historyStep <= $scope.history.length-1) {  
    $scope.historyStep++;
    $scope.topLayer.destroy();  
    var layer = $scope.history[$scope.historyStep-1].clone(); 
    if($scope.historyStep==0){
      $scope.topLayerAdd(2);   // will put empty layer
    }
    else{
      $scope.topLayerAdd(1,layer); 
    } 
    $scope.topLayer.draw();  
  } 
};

works perfectly for me.

Answer 3

I was able to implement a simple solution based on a post by Chtiwi Malek at CodiCode. I also used some of the code from this problem as an example to draw rectangles, so credits go to them and Chtiwi.

The only difference in my solution is I used toJSON() to store each layer state in an array instead of toDataURL() on the canvas. I think toJSON() is needed over toDataURL() to be able to serialize all the data necessary to store each action on the canvas, but I'm not 100% on this so if someone else knows please leave a comment.

function makeHistory() {
    historyStep++;
    if (historyStep < history.length) {
        history.length = historyStep;
    }
    json = layer.toJSON();
    history.push(json);
}

Call this function everytime you want to save a step to undo or redo. In my case, I call this function on every mouseup event.

Bind these 2 functions to the Undo/Redo events.

function undoHistory() {
    if (historyStep > 0) {
        historyStep--;
        layer.destroy();
        layer = Kinetic.Node.create(history[historyStep], 'container')
        stage.add(layer);
    }
}

function redoHistory() {
    if (historyStep < history.length-1) {
        historyStep++;
        layer.destroy();
        layer = Kinetic.Node.create(history[historyStep], 'container')
        stage.add(layer);
    }
}

Here's the jsfiddle. Don't forget to initialize the array and step counter up top. Good luck!

Answer 4

I am not familiar with KineticJS, but the approach should be similar to the provided demo (that also uses a canvas).

Perhaps another example helps. Let's say I have an app to create/move/delete colored shapes that represent musical notes. I have a way to click-drag and highlight a selection of notes. Pressing Delete on the keyboard invokes the function onDeleteGroup:

onDeleteGroup: function(gridModel) {
    // collect all notes in an array
    // ...
    this._deleteGroup(notes);
    this.undoManager.register(
        this, this._createGroup, [notes], 'Undo delete',
        this, this._deleteGroup, [notes], 'Redo delete'
    );
}

All notes are deleted, and 2 methods are registered with the undo manager:

1. The undo function (undo of delete will be create)
2. The redo function (after undo/create will be delete again)

Both functions are straightforward:

_deleteGroup:function(notes) {
    // removes each note from the model
    // thereby removing them from the canvas
    // ...
}

_createGroup:function(notes) {
    // add each note to the model
    // thereby adding them to the canvas
    // ...
}

As you can see, the data object (array of notes) is passed around for creation and deleting. You can do the same for manipulating singular objects.