src/dom/position.js
/**
* @license Copyright (c) 2003-2020, CKSource - Frederico Knabben. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
*/
/**
* @module utils/dom/position
*/
import global from './global';
import Rect from './rect';
import getPositionedAncestor from './getpositionedancestor';
import getBorderWidths from './getborderwidths';
import { isFunction } from 'lodash-es';
/**
* Calculates the `position: absolute` coordinates of a given element so it can be positioned with respect to the
* target in the visually most efficient way, taking various restrictions like viewport or limiter geometry
* into consideration.
*
* // The element which is to be positioned.
* const element = document.body.querySelector( '#toolbar' );
*
* // A target to which the element is positioned relatively.
* const target = document.body.querySelector( '#container' );
*
* // Finding the optimal coordinates for the positioning.
* const { left, top, name } = getOptimalPosition( {
* element: element,
* target: target,
*
* // The algorithm will chose among these positions to meet the requirements such
* // as "limiter" element or "fitInViewport", set below. The positions are considered
* // in the order of the array.
* positions: [
* //
* // [ Target ]
* // +-----------------+
* // | Element |
* // +-----------------+
* //
* targetRect => ( {
* top: targetRect.bottom,
* left: targetRect.left,
* name: 'mySouthEastPosition'
* } ),
*
* //
* // +-----------------+
* // | Element |
* // +-----------------+
* // [ Target ]
* //
* ( targetRect, elementRect ) => ( {
* top: targetRect.top - elementRect.height,
* left: targetRect.left,
* name: 'myNorthEastPosition'
* } )
* ],
*
* // Find a position such guarantees the element remains within visible boundaries of <body>.
* limiter: document.body,
*
* // Find a position such guarantees the element remains within visible boundaries of the browser viewport.
* fitInViewport: true
* } );
*
* // The best position which fits into document.body and the viewport. May be useful
* // to set proper class on the `element`.
* console.log( name ); // -> "myNorthEastPosition"
*
* // Using the absolute coordinates which has been found to position the element
* // as in the diagram depicting the "myNorthEastPosition" position.
* element.style.top = top;
* element.style.left = left;
*
* @param {module:utils/dom/position~Options} options Positioning options object.
* @returns {module:utils/dom/position~Position}
*/
export function getOptimalPosition( { element, target, positions, limiter, fitInViewport } ) {
// If the {@link module:utils/dom/position~Options#target} is a function, use what it returns.
// https://github.com/ckeditor/ckeditor5-utils/issues/157
if ( isFunction( target ) ) {
target = target();
}
// If the {@link module:utils/dom/position~Options#limiter} is a function, use what it returns.
// https://github.com/ckeditor/ckeditor5-ui/issues/260
if ( isFunction( limiter ) ) {
limiter = limiter();
}
const positionedElementAncestor = getPositionedAncestor( element );
const elementRect = new Rect( element );
const targetRect = new Rect( target );
let bestPositionRect;
let bestPositionName;
// If there are no limits, just grab the very first position and be done with that drama.
if ( !limiter && !fitInViewport ) {
[ bestPositionName, bestPositionRect ] = getPositionNameAndRect( positions[ 0 ], targetRect, elementRect );
} else {
const limiterRect = limiter && new Rect( limiter ).getVisible();
const viewportRect = fitInViewport && new Rect( global.window );
const bestPosition = getBestPositionNameAndRect( positions, { targetRect, elementRect, limiterRect, viewportRect } );
// If there's no best position found, i.e. when all intersections have no area because
// rects have no width or height, then just use the first available position.
[ bestPositionName, bestPositionRect ] = bestPosition || getPositionNameAndRect( positions[ 0 ], targetRect, elementRect );
}
let absoluteRectCoordinates = getAbsoluteRectCoordinates( bestPositionRect );
if ( positionedElementAncestor ) {
absoluteRectCoordinates = shiftRectCoordinatesDueToPositionedAncestor( absoluteRectCoordinates, positionedElementAncestor );
}
return {
left: absoluteRectCoordinates.left,
top: absoluteRectCoordinates.top,
name: bestPositionName
};
}
// For given position function, returns a corresponding `Rect` instance.
//
// @private
// @param {Function} position A function returning {@link module:utils/dom/position~Position}.
// @param {utils/dom/rect~Rect} targetRect A rect of the target.
// @param {utils/dom/rect~Rect} elementRect A rect of positioned element.
// @returns {Array} An array containing position name and its Rect.
function getPositionNameAndRect( position, targetRect, elementRect ) {
const { left, top, name } = position( targetRect, elementRect );
return [ name, elementRect.clone().moveTo( left, top ) ];
}
// For a given array of positioning functions, returns such that provides the best
// fit of the `elementRect` into the `limiterRect` and `viewportRect`.
//
// @private
//
// @param {Object} options
// @param {module:utils/dom/position~Options#positions} positions Functions returning {@link module:utils/dom/position~Position}
// to be checked, in the order of preference.
// @param {Object} options
// @param {utils/dom/rect~Rect} options.targetRect A rect of the {@link module:utils/dom/position~Options#target}.
// @param {utils/dom/rect~Rect} options.elementRect A rect of positioned {@link module:utils/dom/position~Options#element}.
// @param {utils/dom/rect~Rect} options.limiterRect A rect of the {@link module:utils/dom/position~Options#limiter}.
// @param {utils/dom/rect~Rect} options.viewportRect A rect of the viewport.
//
// @returns {Array} An array containing the name of the position and it's rect.
function getBestPositionNameAndRect( positions, options ) {
const { elementRect, viewportRect } = options;
// This is when element is fully visible.
const elementRectArea = elementRect.getArea();
// Let's calculate intersection areas for positions. It will end early if best match is found.
const processedPositions = processPositionsToAreas( positions, options );
// First let's check all positions that fully fit in the viewport.
if ( viewportRect ) {
const processedPositionsInViewport = processedPositions.filter( ( { viewportIntersectArea } ) => {
return viewportIntersectArea === elementRectArea;
} );
// Try to find best position from those which fit completely in viewport.
const bestPositionData = getBestOfProcessedPositions( processedPositionsInViewport, elementRectArea );
if ( bestPositionData ) {
return bestPositionData;
}
}
// Either there is no viewportRect or there is no position that fits completely in the viewport.
return getBestOfProcessedPositions( processedPositions, elementRectArea );
}
// For a given array of positioning functions, calculates intersection areas for them.
//
// Note: If some position fully fits into the `limiterRect`, it will be returned early, without further consideration
// of other positions.
//
// @private
//
// @param {module:utils/dom/position~Options#positions} positions Functions returning {@link module:utils/dom/position~Position}
// to be checked, in the order of preference.
// @param {Object} options
// @param {utils/dom/rect~Rect} options.targetRect A rect of the {@link module:utils/dom/position~Options#target}.
// @param {utils/dom/rect~Rect} options.elementRect A rect of positioned {@link module:utils/dom/position~Options#element}.
// @param {utils/dom/rect~Rect} options.limiterRect A rect of the {@link module:utils/dom/position~Options#limiter}.
// @param {utils/dom/rect~Rect} options.viewportRect A rect of the viewport.
//
// @returns {Array.<Object>} Array of positions with calculated intersection areas. Each item is an object containing:
// * {String} positionName Name of position.
// * {utils/dom/rect~Rect} positionRect Rect of position.
// * {Number} limiterIntersectArea Area of intersection of the position with limiter part that is in the viewport.
// * {Number} viewportIntersectArea Area of intersection of the position with viewport.
function processPositionsToAreas( positions, { targetRect, elementRect, limiterRect, viewportRect } ) {
const processedPositions = [];
// This is when element is fully visible.
const elementRectArea = elementRect.getArea();
for ( const position of positions ) {
const [ positionName, positionRect ] = getPositionNameAndRect( position, targetRect, elementRect );
let limiterIntersectArea = 0;
let viewportIntersectArea = 0;
if ( limiterRect ) {
if ( viewportRect ) {
// Consider only the part of the limiter which is visible in the viewport. So the limiter is getting limited.
const limiterViewportIntersectRect = limiterRect.getIntersection( viewportRect );
if ( limiterViewportIntersectRect ) {
// If the limiter is within the viewport, then check the intersection between that part of the
// limiter and actual position.
limiterIntersectArea = limiterViewportIntersectRect.getIntersectionArea( positionRect );
}
} else {
limiterIntersectArea = limiterRect.getIntersectionArea( positionRect );
}
}
if ( viewportRect ) {
viewportIntersectArea = viewportRect.getIntersectionArea( positionRect );
}
const processedPosition = {
positionName,
positionRect,
limiterIntersectArea,
viewportIntersectArea
};
// If a such position is found that element is fully contained by the limiter then, obviously,
// there will be no better one, so finishing.
if ( limiterIntersectArea === elementRectArea ) {
return [ processedPosition ];
}
processedPositions.push( processedPosition );
}
return processedPositions;
}
// For a given array of processed position data (with calculated Rects for positions and intersection areas)
// returns such that provides the best fit of the `elementRect` into the `limiterRect` and `viewportRect` at the same time.
//
// **Note**: It will return early if some position fully fits into the `limiterRect`.
//
// @private
// @param {Array.<Object>} Array of positions with calculated intersection areas (in order of preference).
// Each item is an object containing:
//
// * {String} positionName Name of position.
// * {utils/dom/rect~Rect} positionRect Rect of position.
// * {Number} limiterIntersectArea Area of intersection of the position with limiter part that is in the viewport.
// * {Number} viewportIntersectArea Area of intersection of the position with viewport.
//
// @param {Number} elementRectArea Area of positioned {@link module:utils/dom/position~Options#element}.
// @returns {Array|null} An array containing the name of the position and it's rect, or null if not found.
function getBestOfProcessedPositions( processedPositions, elementRectArea ) {
let maxFitFactor = 0;
let bestPositionRect;
let bestPositionName;
for ( const { positionName, positionRect, limiterIntersectArea, viewportIntersectArea } of processedPositions ) {
// If a such position is found that element is fully container by the limiter then, obviously,
// there will be no better one, so finishing.
if ( limiterIntersectArea === elementRectArea ) {
return [ positionName, positionRect ];
}
// To maximize both viewport and limiter intersection areas we use distance on viewportIntersectArea
// and limiterIntersectArea plane (without sqrt because we are looking for max value).
const fitFactor = viewportIntersectArea ** 2 + limiterIntersectArea ** 2;
if ( fitFactor > maxFitFactor ) {
maxFitFactor = fitFactor;
bestPositionRect = positionRect;
bestPositionName = positionName;
}
}
return bestPositionRect ? [ bestPositionName, bestPositionRect ] : null;
}
// For a given absolute Rect coordinates object and a positioned element ancestor, it returns an object with
// new Rect coordinates that make up for the position and the scroll of the ancestor.
//
// This is necessary because while Rects (and DOMRects) are relative to the browser's viewport, their coordinates
// are used in real–life to position elements with `position: absolute`, which are scoped by any positioned
// (and scrollable) ancestors.
//
// @private
//
// @param {Object} absoluteRectCoordinates An object with absolute rect coordinates.
// @param {Object} absoluteRectCoordinates.top
// @param {Object} absoluteRectCoordinates.left
// @param {HTMLElement} positionedElementAncestor An ancestor element that should be considered.
//
// @returns {Object} An object corresponding to `absoluteRectCoordinates` input but with values shifted
// to make up for the positioned element ancestor.
function shiftRectCoordinatesDueToPositionedAncestor( { left, top }, positionedElementAncestor ) {
const ancestorPosition = getAbsoluteRectCoordinates( new Rect( positionedElementAncestor ) );
const ancestorBorderWidths = getBorderWidths( positionedElementAncestor );
// (https://github.com/ckeditor/ckeditor5-ui-default/issues/126)
// If there's some positioned ancestor of the panel, then its `Rect` must be taken into
// consideration. `Rect` is always relative to the viewport while `position: absolute` works
// with respect to that positioned ancestor.
left -= ancestorPosition.left;
top -= ancestorPosition.top;
// (https://github.com/ckeditor/ckeditor5-utils/issues/139)
// If there's some positioned ancestor of the panel, not only its position must be taken into
// consideration (see above) but also its internal scrolls. Scroll have an impact here because `Rect`
// is relative to the viewport (it doesn't care about scrolling), while `position: absolute`
// must compensate that scrolling.
left += positionedElementAncestor.scrollLeft;
top += positionedElementAncestor.scrollTop;
// (https://github.com/ckeditor/ckeditor5-utils/issues/139)
// If there's some positioned ancestor of the panel, then its `Rect` includes its CSS `borderWidth`
// while `position: absolute` positioning does not consider it.
// E.g. `{ position: absolute, top: 0, left: 0 }` means upper left corner of the element,
// not upper-left corner of its border.
left -= ancestorBorderWidths.left;
top -= ancestorBorderWidths.top;
return { left, top };
}
// DOMRect (also Rect) works in a scroll–independent geometry but `position: absolute` doesn't.
// This function converts Rect to `position: absolute` coordinates.
//
// @private
// @param {utils/dom/rect~Rect} rect A rect to be converted.
// @returns {Object} Object containing `left` and `top` properties, in absolute coordinates.
function getAbsoluteRectCoordinates( { left, top } ) {
const { scrollX, scrollY } = global.window;
return {
left: left + scrollX,
top: top + scrollY
};
}
/**
* The `getOptimalPosition` helper options.
*
* @interface module:utils/dom/position~Options
*/
/**
* Element that is to be positioned.
*
* @member {HTMLElement} #element
*/
/**
* Target with respect to which the `element` is to be positioned.
*
* @member {HTMLElement|Range|ClientRect|Rect|Function} #target
*/
/**
* An array of functions which return {@link module:utils/dom/position~Position} relative
* to the `target`, in the order of preference.
*
* @member {Array.<Function>} #positions
*/
/**
* When set, the algorithm will chose position which fits the most in the
* limiter's bounding rect.
*
* @member {HTMLElement|Range|ClientRect|Rect|Function} #limiter
*/
/**
* When set, the algorithm will chose such a position which fits `element`
* the most inside visible viewport.
*
* @member {Boolean} #fitInViewport
*/
/**
* An object describing a position in `position: absolute` coordinate
* system, along with position name.
*
* @typedef {Object} module:utils/dom/position~Position
*
* @property {Number} top Top position offset.
* @property {Number} left Left position offset.
* @property {String} name Name of the position.
*/