_touchstartFromDom = function(e) {
        var game = enchant.Game.instance;
        var group;
        for (var i = canvasGroupInstances.length - 1; i >= 0; i--) {
            group = canvasGroupInstances[i];
            if (group.scene !== game.currentScene) {
                continue;
            }
            var sp = group._touchstartPropagation(e);
            if (sp) {
                touchingEntity = sp;
                touchingGroup = group;
                return;
            }
        }
    }
scaling of group in the direction of y axis
@see enchant.CanvasGroup.originX
@see enchant.CanvasGroup.originY
@type {Number}