ant-design/components/popover/placements.tsx

const autoAdjustOverflow = {
  adjustX: 1,
  adjustY: 1,
};

const targetOffset = [0, 0];

export default function getPlacements(config = {}) {
  const { arrowWidth = 5, horizontalArrowShift = 16, verticalArrowShift = 12 } = config;
  return {
    left: {
      points: ['cr', 'cl'],
      overflow: autoAdjustOverflow,
      offset: [-4, 0],
      targetOffset,
    },
    right: {
      points: ['cl', 'cr'],
      overflow: autoAdjustOverflow,
      offset: [4, 0],
      targetOffset,
    },
    top: {
      points: ['bc', 'tc'],
      overflow: autoAdjustOverflow,
      offset: [0, -4],
      targetOffset,
    },
    bottom: {
      points: ['tc', 'bc'],
      overflow: autoAdjustOverflow,
      offset: [0, 4],
      targetOffset,
    },
    topLeft: {
      points: ['bl', 'tc'],
      overflow: autoAdjustOverflow,
      offset: [-(horizontalArrowShift + arrowWidth), -4],
      targetOffset,
    },
    leftTop: {
      points: ['tr', 'cl'],
      overflow: autoAdjustOverflow,
      offset: [-4, -(verticalArrowShift + arrowWidth)],
      targetOffset,
    },
    topRight: {
      points: ['br', 'tc'],
      overflow: autoAdjustOverflow,
      offset: [horizontalArrowShift + arrowWidth, -4],
      targetOffset,
    },
    rightTop: {
      points: ['tl', 'cr'],
      overflow: autoAdjustOverflow,
      offset: [4, -(verticalArrowShift + arrowWidth)],
      targetOffset,
    },
    bottomRight: {
      points: ['tr', 'bc'],
      overflow: autoAdjustOverflow,
      offset: [horizontalArrowShift + arrowWidth, 4],
      targetOffset,
    },
    rightBottom: {
      points: ['bl', 'cr'],
      overflow: autoAdjustOverflow,
      offset: [4, verticalArrowShift + arrowWidth],
      targetOffset,
    },
    bottomLeft: {
      points: ['tl', 'bc'],
      overflow: autoAdjustOverflow,
      offset: [-(horizontalArrowShift + arrowWidth), 4],
      targetOffset,
    },
    leftBottom: {
      points: ['br', 'cl'],
      overflow: autoAdjustOverflow,
      offset: [-4, verticalArrowShift + arrowWidth],
      targetOffset,
    },
  };
}