en/builder/src/echarts3/component/helper/sliderMove.js

/**
 * Calculate slider move result.
 * Usage:
 * (1) If both handle0 and handle1 are needed to be moved, set minSpan the same as
 * maxSpan and the same as `Math.abs(handleEnd[1] - handleEnds[0])`.
 * (2) If handle0 is forbidden to cross handle1, set minSpan as `0`.
 *
 * @param {number} delta Move length.
 * @param {Array.<number>} handleEnds handleEnds[0] can be bigger then handleEnds[1].
 *              handleEnds will be modified in this method.
 * @param {Array.<number>} extent handleEnds is restricted by extent.
 *              extent[0] should less or equals than extent[1].
 * @param {number|string} handleIndex Can be 'all', means that both move the two handleEnds,
 *              where the input minSpan and maxSpan will not work.
 * @param {number} [minSpan] The range of dataZoom can not be smaller than that.
 *              If not set, handle0 and cross handle1. If set as a non-negative
 *              number (including `0`), handles will push each other when reaching
 *              the minSpan.
 * @param {number} [maxSpan] The range of dataZoom can not be larger than that.
 * @return {Array.<number>} The input handleEnds.
 */
export default function (delta, handleEnds, extent, handleIndex, minSpan, maxSpan) {
  // Normalize firstly.
  handleEnds[0] = restrict(handleEnds[0], extent);
  handleEnds[1] = restrict(handleEnds[1], extent);
  delta = delta || 0;
  var extentSpan = extent[1] - extent[0]; // Notice maxSpan and minSpan can be null/undefined.

  if (minSpan != null) {
    minSpan = restrict(minSpan, [0, extentSpan]);
  }

  if (maxSpan != null) {
    maxSpan = Math.max(maxSpan, minSpan != null ? minSpan : 0);
  }

  if (handleIndex === 'all') {
    minSpan = maxSpan = Math.abs(handleEnds[1] - handleEnds[0]);
    handleIndex = 0;
  }

  var originalDistSign = getSpanSign(handleEnds, handleIndex);
  handleEnds[handleIndex] += delta; // Restrict in extent.

  var extentMinSpan = minSpan || 0;
  var realExtent = extent.slice();
  originalDistSign.sign < 0 ? realExtent[0] += extentMinSpan : realExtent[1] -= extentMinSpan;
  handleEnds[handleIndex] = restrict(handleEnds[handleIndex], realExtent); // Expand span.

  var currDistSign = getSpanSign(handleEnds, handleIndex);

  if (minSpan != null && (currDistSign.sign !== originalDistSign.sign || currDistSign.span < minSpan)) {
    // If minSpan exists, 'cross' is forbinden.
    handleEnds[1 - handleIndex] = handleEnds[handleIndex] + originalDistSign.sign * minSpan;
  } // Shrink span.


  var currDistSign = getSpanSign(handleEnds, handleIndex);

  if (maxSpan != null && currDistSign.span > maxSpan) {
    handleEnds[1 - handleIndex] = handleEnds[handleIndex] + currDistSign.sign * maxSpan;
  }

  return handleEnds;
}

function getSpanSign(handleEnds, handleIndex) {
  var dist = handleEnds[handleIndex] - handleEnds[1 - handleIndex]; // If `handleEnds[0] === handleEnds[1]`, always believe that handleEnd[0]
  // is at left of handleEnds[1] for non-cross case.

  return {
    span: Math.abs(dist),
    sign: dist > 0 ? -1 : dist < 0 ? 1 : handleIndex ? -1 : 1
  };
}

function restrict(value, extend) {
  return Math.min(extend[1], Math.max(extend[0], value));
}