Function transitionBetween

src/animation/universalTransition.ts:209–511

(
    oldList: TransitionSeries[],
    newList: TransitionSeries[],
    api: ExtensionAPI
)

}

function transitionBetween(
    oldList: TransitionSeries[],
    newList: TransitionSeries[],
    api: ExtensionAPI
) {

    const oldDiffItems = flattenDataDiffItems(oldList);
    const newDiffItems = flattenDataDiffItems(newList);

    function updateMorphingPathProps(
        from: Path, to: Path,
        rawFrom: Path, rawTo: Path,
        animationCfg: ElementAnimateConfig
    ) {
        if (rawFrom || from) {
            to.animateFrom({
                style: (rawFrom && rawFrom !== from)
                    // dividingMethod like clone may override the style(opacity)
                    // So extend it to raw style.
                    ? extend(extend({}, rawFrom.style), from.style)
                    : from.style
            }, animationCfg);
        }
    }

    let hasMorphAnimation = false;

    /**
     * With groupId and childGroupId, we can build parent-child relationships between dataItems.
     * However, we should mind the parent-child "direction" between old and new options.
     *
     * For example, suppose we have two dataItems from two series.data:
     *
     * dataA: [                          dataB: [
     *   {                                 {
     *     value: 5,                         value: 3,
     *     groupId: 'creatures',             groupId: 'animals',
     *     childGroupId: 'animals'           childGroupId: 'dogs'
     *   },                                },
     *   ...                               ...
     * ]                                 ]
     *
     * where dataA is belong to optionA and dataB is belong to optionB.
     *
     * When we `setOption(optionB)` from optionA, we choose childGroupId of dataItemA and groupId of
     * dataItemB as keys so the two keys are matched (both are 'animals'), then universalTransition
     * will work. This derection is "parent -> child".
     *
     * If we `setOption(optionA)` from optionB, we also choose groupId of dataItemB and childGroupId
     * of dataItemA as keys and universalTransition will work. This derection is "child -> parent".
     *
     * If there is no childGroupId specified, which means no multiLevelDrillDown/Up is needed and no
     * parent-child relationship exists. This direction is "none".
     *
     * So we need to know whether to use groupId or childGroupId as the key when we call the keyGetter
     * functions. Thus, we need to decide the direction first.
     *
     * The rule is: