echarts sliderMove 源码

echarts sliderMove 代码

文件路径：/src/component/helper/sliderMove.ts

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/

/**
 * 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 delta Move length.
 * @param handleEnds handleEnds[0] can be bigger then handleEnds[1].
 *              handleEnds will be modified in this method.
 * @param extent handleEnds is restricted by extent.
 *              extent[0] should less or equals than extent[1].
 * @param handleIndex Can be 'all', means that both move the two handleEnds.
 * @param 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 maxSpan The range of dataZoom can not be larger than that.
 * @return The input handleEnds.
 */
export default function sliderMove(
    delta: number,
    handleEnds: number[],
    extent: number[],
    handleIndex: 'all' | 0 | 1,
    minSpan?: number,
    maxSpan?: number
): number[] {

    delta = delta || 0;

    const 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') {
        let handleSpan = Math.abs(handleEnds[1] - handleEnds[0]);
        handleSpan = restrict(handleSpan, [0, extentSpan]);
        minSpan = maxSpan = restrict(handleSpan, [minSpan, maxSpan]);
        handleIndex = 0;
    }

    handleEnds[0] = restrict(handleEnds[0], extent);
    handleEnds[1] = restrict(handleEnds[1], extent);

    const originalDistSign = getSpanSign(handleEnds, handleIndex);

    handleEnds[handleIndex] += delta;

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

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

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

    return handleEnds;
}

function getSpanSign(handleEnds: number[], handleIndex: 0 | 1) {
    const 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: number, extend: number[]) {
    return Math.min(
        extend[1] != null ? extend[1] : Infinity,
        Math.max(extend[0] != null ? extend[0] : -Infinity, value)
    );
}

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