function createPageButton(name, iconIdx) {
            var pageDataIndexName = name + 'DataIndex';
            var icon = createIcon(
                legendModel.get('pageIcons', true)[legendModel.getOrient().name][iconIdx],
                {
                    // Buttons will be created in each render, so we do not need
                    // to worry about avoiding using legendModel kept in scope.
                    onclick: bind(
                        me._pageGo, me, pageDataIndexName, legendModel, api
                    )
                },
                {
                    x: -pageIconSize[0] / 2,
                    y: -pageIconSize[1] / 2,
                    width: pageIconSize[0],
                    height: pageIconSize[1]
                }
            );
            icon.name = name;
            controllerGroup.add(icon);
        }
@param {module:echarts/model/Model} legendModel
@return {Object} {
 contentPosition: Array.<number>, null when data item not found.
 pageIndex: number, null when data item not found.
 pageCount: number, always be a number, can be 0.
 pagePrevDataIndex: number, null when no previous page.
 pageNextDataIndex: number, null when no next page.
}