overscroll/es/actions.js

scroll

export default (function (scope) {
  var target = scope.target,
      win = scope.win,
      overscroll = scope.overscroll,
      isPageScroll = scope.isPageScroll,
      resetState = scope.resetState,
      getScroll = scope.getScroll,
      getFromRange = scope.getFromRange,
      getScrollSize = scope.getScrollSize,
      getClientSize = scope.getClientSize;


  function setScroll() {
    var scrollLeft = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : overscroll.scrollLeft;
    var scrollTop = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : overscroll.scrollTop;

    // 取出滚动区域大小和可视范围计算滚动位置
    var scrollTopRange = overscroll.scrollTopRange,
        scrollLeftRange = overscroll.scrollLeftRange;

    var newScrollTop = scrollTopRange(scrollTop);
    var newScrollLeft = scrollLeftRange(scrollLeft);

    // 重置dom状态
    resetState(newScrollTop, newScrollLeft);

    // 缓存滚动条位置
    overscroll.scrollLeft = newScrollLeft;
    overscroll.scrollTop = newScrollTop;
    if (isPageScroll) {
      win.scrollTo(overscroll.scrollLeft, overscroll.scrollTop);
    } else {
      target.scrollTop = overscroll.scrollTop;
      target.scrollLeft = overscroll.scrollLeft;
    }
  }

  function resetCache() {
    var _getScroll = getScroll(),
        top = _getScroll.top,
        left = _getScroll.left;

    var _getScrollSize = getScrollSize(),
        scrollWidth = _getScrollSize.width,
        scrollHeight = _getScrollSize.height;

    var _getClientSize = getClientSize(),
        clientWidth = _getClientSize.width,
        clientHeight = _getClientSize.height;

    overscroll.scrollTop = top;
    overscroll.scrollLeft = left;
    overscroll.scrollWidth = scrollWidth;
    overscroll.scrollHeight = scrollHeight;
    overscroll.clientWidth = clientWidth;
    overscroll.clientHeight = clientHeight;
    overscroll.scrollTopRange = getFromRange(0, scrollHeight - clientHeight);
    overscroll.scrollLeftRange = getFromRange(0, scrollWidth - clientWidth);
  }

  return {
    setScroll: setScroll, resetCache: resetCache
  };
});