@deboxsoft/react-native-elements/src/tooltip/getTooltipCoordinate.js

React Native Elements & UI Toolkit

const getArea = (a, b) => a * b;

const getPointDistance = (a, b) =>
  Math.sqrt(Math.pow(a[0] - b[0], 2) + Math.pow(a[1] - b[1], 2));

/*
type Coord = {
  x: number,
  y: number,
};

  ~Tooltip coordinate system:~
  The tooltip coordinates are based on the element which it is wrapping.
  We take the x and y coordinates of the element and find the best position
  to place the tooltip. To find the best position we look for the side with the
  most space. In order to find the side with the most space we divide the the 
  surroundings in four quadrants and check for the one with biggest area.
  Once we know the quandrant with the biggest area it place the tooltip in that
  direction.

  To find the areas we first get 5 coordinate points. The center and the other 4 extreme points
  which together make a perfect cross shape.

  Once we know the coordincates we can get the length of the vertices which form each quadrant.
  Since they are squares we only need two.
*/

const getTooltipCoordinate = (
  x,
  y,
  width,
  height,
  ScreenWidth,
  ScreenHeight,
  tooltipWidth,
  tooltipHeight,
  withPointer,
) => {
  // The following are point coordinates: [x, y]
  const center = [x + width / 2, y + height / 2];
  const pOne = [center[0], 0];
  const pTwo = [ScreenWidth, center[1]];
  const pThree = [center[0], ScreenHeight];
  const pFour = [0, center[1]];

  // vertices
  const vOne = getPointDistance(center, pOne);
  const vTwo = getPointDistance(center, pTwo);
  const vThree = getPointDistance(center, pThree);
  const vFour = getPointDistance(center, pFour);

  // Quadrant areas.
  // type Areas = {
  //   area: number,
  //   id: number,
  // };

  const areas = [
    getArea(vOne, vFour),
    getArea(vOne, vTwo),
    getArea(vTwo, vThree),
    getArea(vThree, vFour),
  ].map((each, index) => ({ area: each, id: index }));

  const sortedArea = areas.sort((a, b) => b.area - a.area);

  // deslocated points
  const dX = 0.001;
  const dY = height / 2;

  // Deslocate the coordinates in the direction of the quadrant.
  const directionCorrection = [[-1, -1], [1, -1], [1, 1], [-1, 1]];
  const deslocateReferencePoint = [
    [-tooltipWidth, -tooltipHeight],
    [0, -tooltipHeight],
    [0, 0],
    [-tooltipWidth, 0],
  ];

  // current quadrant index
  const qIndex = sortedArea[0].id;

  const getWithPointerOffsetY = () =>
    withPointer ? 10 * directionCorrection[qIndex][1] : 0;
  const getWithPointerOffsetX = () =>
    withPointer ? center[0] - 18 * directionCorrection[qIndex][0] : center[0];

  const newX =
    getWithPointerOffsetX() +
    (dX * directionCorrection[qIndex][0] + deslocateReferencePoint[qIndex][0]);

  return {
    x: constraintX(newX, qIndex, center[0], ScreenWidth, tooltipWidth),
    y:
      center[1] +
      (dY * directionCorrection[qIndex][1] +
        deslocateReferencePoint[qIndex][1]) +
      getWithPointerOffsetY(),
  };
};

const constraintX = (
  newX,
  qIndex,
  x,
  ScreenWidth,
  tooltipWidth,
) => {
  switch (qIndex) {
    // 0 and 3 are the left side quadrants.
    case 0:
    case 3: {
      const maxWidth = newX > ScreenWidth ? ScreenWidth - 10 : newX;
      return newX < 1 ? 10 : maxWidth;
    }
    // 1 and 2 are the right side quadrants
    case 1:
    case 2: {
      const leftOverSpace = ScreenWidth - newX;
      return leftOverSpace >= tooltipWidth
        ? newX
        : newX - (tooltipWidth - leftOverSpace + 10);
    }
    default: {
      return 0;
    }
  }
};

export default getTooltipCoordinate;