code: function ViewStackLayout(context, options) {
          var set = {
              size: context.size,
              translate: [0, 0, 0]
          };
          this._size[0] = context.size[0];
          this._size[1] = context.size[1];
          var views = context.get('views');
          var transferables = context.get('transferables');
          var visibleCount = 0;
          for (var i = 0; i < views.length; i++) {
              var item = this._viewStack[i];
              switch (item.state) {
                  case ItemState.HIDDEN:
                      context.set(views[i], {
                          size: context.size,
                          translate: [context.size[0] * 2, context.size[1] * 2, 0]
                      });
                      break;
  
                  case ItemState.HIDE:
                  case ItemState.HIDING:
                  case ItemState.VISIBLE:
                  case ItemState.SHOW:
                  case ItemState.SHOWING:
                      if (visibleCount < 2) {
                          visibleCount++;
  
                          // Layout view
                          var view = views[i];
                          context.set(view, set);
  
                          // Layout any transferables
                          for (var j = 0; j < transferables.length; j++) {
                              for (var k = 0; k < item.transferables.length; k++) {
                                  if (transferables[j].renderNode === item.transferables[k].renderNode) {
                                      context.set(transferables[j], {
                                          translate: [0, 0, set.translate[2]],
                                          size: [context.size[0], context.size[1]]
                                      });
                                  }
                              }
                          }
  
                          // Increase z-index for next view
                          set.translate[2] += options.zIndexOffset;
                      }
                      break;
              }
          }
      }
docs: Stacks the renderables on top of each other
  with a z-translation of this.options.zIndexOffset.