Function position

src/js/constraint.js:299–466

({ top, left, targetAttachment })

export default {
  position({ top, left, targetAttachment }) {
    if (!this.options.constraints) {
      return true;
    }

    let { height, width } = this.cache('element-bounds', () => {
      return getBounds(this.bodyElement, this.element);
    });

    if (width === 0 && height === 0 && !isUndefined(this.lastSize)) {
      // Handle the item getting hidden as a result of our positioning without glitching
      // the classes in and out
      ({ width, height } = this.lastSize);
    }

    const targetSize = this.cache('target-bounds', () => {
      return this.getTargetBounds();
    });

    const { height: targetHeight, width: targetWidth } = targetSize;
    const { classes, classPrefix } = this.options;

    const allClasses = _getAllClasses(classes, classPrefix, this.options.constraints);
    const addClasses = [];

    const tAttachment = extend({}, targetAttachment);
    const eAttachment = extend({}, this.attachment);

    this.options.constraints.forEach((constraint) => {
      let { to, attachment, pin } = constraint;

      if (isUndefined(attachment)) {
        attachment = '';
      }

      let changeAttachX, changeAttachY;
      if (attachment.indexOf(' ') >= 0) {
        [changeAttachY, changeAttachX] = attachment.split(' ');
      } else {
        changeAttachX = changeAttachY = attachment;
      }

      const bounds = getBoundingRect(this.bodyElement, this, to);

      if (changeAttachY === 'target' || changeAttachY === 'both') {
        if (top < bounds[1] && tAttachment.top === 'top') {
          top += targetHeight;
          tAttachment.top = 'bottom';
        }

        if (top + height > bounds[3] && tAttachment.top === 'bottom') {
          top -= targetHeight;
          tAttachment.top = 'top';
        }
      }

      if (changeAttachY === 'together') {
        top = _flipYTogether(tAttachment, eAttachment, bounds, height, targetHeight, top);