docs: function () {
              var prev, page,
                  state = this.state,
                  pages = state.pages;
  
              prev = util.bisectRight(pages, state.scrollLeft, 'x0') - 1;
              page = util.bisectRight(pages, state.scrollLeft + pages[prev].width / 2, 'x0') - 1;
              return 1 + page;
          }