Method undo

docs/app/js/sanddance-app.js:14244–14252

()

            });
        }
        undo() {
            const historyIndex = this.state.historyIndex - 1;
            if (historyIndex < 0) return;
            const newState = this.replay(historyIndex);
            this.rebaseFilter = true;
            this.setState(Object.assign(Object.assign({}, newState), {
                historyIndex
            }));
        }
        redo(historyIndex = this.state.historyIndex + 1) {
            if (historyIndex >= this.state.historyItems.length) return;
            const newState = this.replay(historyIndex);