+ ifChanged: function(context, action, documentChangedHandler, documentUnchangedHandler) {
+ var hasChanged = false,
+ changeMonitor = function() {
+ hasChanged = true;
+ };
+
+ this.on('change', changeMonitor);
+ action.call(context);
+ this.off('change', changeMonitor);
+
+ if(hasChanged) {
+ if(documentChangedHandler) {
+ documentChangedHandler.call(context);
+ }
+ } else {
+ if(documentUnchangedHandler) {
+ documentUnchangedHandler.call(context);
+ }
+ }
+ },
+
+ transform: function(Transformation, args) {
+ var toret, transformation;
+
+ if(!this._currentTransaction) {
+ return this.transaction(function() {
+ return this.transform(Transformation, args);
+ }, {context: this});
+ }
+
+ if(typeof Transformation === 'function') {
+ transformation = new Transformation(this, this, args);
+ } else {
+ transformation = Transformation;
+ }
+ if(transformation) {
+ this._transformationLevel++;
+
+ this.ifChanged(
+ this,
+ function() {
+ toret = transformation.run({beUndoable:this._transformationLevel === 1});
+ },
+ function() {
+ if(this._transformationLevel === 1 && !this._undoInProgress) {
+ this._currentTransaction.pushTransformation(transformation);
+ this.redoStack = [];
+ }
+ }
+ );
+
+ this._transformationLevel--;
+ return toret;
+ } else {
+ throw new Error('Transformation ' + transformation + ' doesn\'t exist!');
+ }
+ },
+ undo: function() {
+ var transaction = this.undoStack.pop(),
+ doc = this,
+ transformations, stopAt;
+
+ if(transaction) {
+ this._undoInProgress = true;
+
+ // We will modify this array in a minute so make sure we work on a copy.
+ transformations = transaction.transformations.slice(0);
+
+ if(transformations.length > 1) {
+ // In case of real transactions we don't want to run undo on all of transformations if we don't have to.
+ transformations.some(function(t, idx) {
+ if(!t.undo && t.getChangeRoot().sameNode(doc.root)) {
+ stopAt = idx;
+ return true; //break
+ }
+ });
+ if(stopAt !== undefined) {
+ // We will get away with undoing only this transformations as the one at stopAt reverses the whole document.
+ transformations = transformations.slice(0, stopAt+1);
+ }
+ }