Platform

Floating UI works on any platform that can run JavaScript, as long as it has adequate measurement APIs for elements. Possible platforms other than the DOM include React Native, Canvas/WebGL, etc.

The library works largely with a Rect:

interface Rect {
  width: number;
  height: number;
  x: number;
  y: number;
}

This data can come from anywhere, and the library will perform the right computations. x and y represent the coordinates of the element relative to another one.

import {computePosition} from '@floating-ui/core';
 
computePosition(referenceElement, floatingElement, {
  platform: {
    // ...
  },
});

Methods

A platform is a plain object consisting of 3 required and 6 optional methods. These methods allow the platform to interface with Floating UI's logic.

Each of these methods can be either async or sync. This enables support of platforms whose measurement APIs are async, like React Native.

Required methods

getElementRects

Takes in the elements and the positioning strategy and returns the element Rect objects.

function getElementRects({reference, floating, strategy}) {
  return {
    reference: {width: 0, height: 0, x: 0, y: 0},
    floating: {width: 0, height: 0, x: 0, y: 0},
  };
}

reference

The x and y values of a reference Rect should be its coordinates relative to the floating element's offsetParent element if required rather than the viewport.

floating

Both x and y are not relevant initially, so you can set these both of these to 0.

getDimensions

Returns the dimensions of an element.

function getDimensions(element) {
  return {width: 0, height: 0};
}

getClippingRect

Returns the Rect (relative to the viewport) whose outside bounds will clip the given element. For instance, the viewport itself.

function getClippingRect({element, boundary, rootBoundary}) {
  return {
    width: 0,
    height: 0,
    x: 0,
    y: 0,
  };
}

Optional methods

Depending on the platform you're working with, these may or may not be necessary.

convertOffsetParentRelativeRectToViewportRelativeRect

This function will take a Rect that is relative to a given offsetParent element and convert its x and y values such that it is instead relative to the viewport.

function convertOffsetParentRelativeRectToViewportRelativeRect({
  rect,
  offsetParent,
  strategy,
}) {
  return rect;
}

getOffsetParent

Returns the offsetParent of a given element. The following four properties are what is accessed on an offsetParent.

function getOffsetParent(element) {
  return {
    clientWidth: 0,
    clientHeight: 0,
    clientLeft: 0,
    clientTop: 0,
  };
}

getDocumentElement

Returns the document element.

function getDocumentElement(element) {
  return {};
}

getClientRects

Returns an array of ClientRects.

function getClientRects(element) {
  return [];
}

isElement

Determines if the current value is an element.

function isElement(value) {
  return true;
}

isRTL

Determines if an element is in RTL layout.

function isRTL(element) {
  return false;
}

Usage

All these methods are passed to platform:

import {computePosition} from '@floating-ui/core';
 
computePosition(referenceEl, floatingEl, {
  platform: {
    // Required
    getElementRects,
    getDimensions,
    getClippingRect,
 
    // Optional
    convertOffsetParentRelativeRectToViewportRelativeRect,
    getOffsetParent,
    getDocumentElement,
    getClientRects,
    isElement,
    isRTL,
  },
});