ckeditor · Reinmar · Dec 8, 2016 · Dec 1, 2016 · Dec 1, 2016 · Dec 1, 2016
diff --git a/src/dom/getpositionedancestor.js b/src/dom/getpositionedancestor.js
@@ -0,0 +1,28 @@
+/**
+ * @license Copyright (c) 2003-2016, CKSource - Frederico Knabben. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+/* globals window */
+
+/**
+ * @module utils/dom/getpositionedancestor
+ */
+
+/**
+ * For a given element, returns the nearest ancestor element which CSS position is not "static".
+ *
+ * @param {HTMLElement} element Native DOM element to be checked.
+ * @returns {HTMLElement|null}
+ */
+export default function getPositionedAncestor( element ) {
+	while ( element && element.tagName.toLowerCase() != 'html' ) {
+		if ( window.getComputedStyle( element ).position != 'static' ) {
+			return element;
+		}
+
+		element = element.parentElement;
+	}
+
+	return null;
+}
diff --git a/src/dom/isrange.js b/src/dom/isrange.js
@@ -0,0 +1,18 @@
+/**
+ * @license Copyright (c) 2003-2016, CKSource - Frederico Knabben. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+/**
+ * @module utils/dom/isrange
+ */
+
+/**
+ * Checks if the object is a native DOM Range.
+ *
+ * @param {*} obj
+ * @returns {Boolean}
+ */
+export default function isRange( obj ) {
+	return Object.prototype.toString.apply( obj ) == '[object Range]';
+}
diff --git a/src/dom/position.js b/src/dom/position.js
@@ -0,0 +1,272 @@
+/**
+ * @license Copyright (c) 2003-2016, CKSource - Frederico Knabben. All rights reserved.
+ * For licensing, see LICENSE.md.
+ */
+
+/* globals window */
+
+/**
+ * @module utils/dom/position
+ */
+
+import Rect from './rect.js';
+import getPositionedAncestor from './getpositionedancestor.js';
+
+/**
+ * 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 } ) {
+	const positionedElementAncestor = getPositionedAncestor( element.parentElement );
+	const elementRect = new Rect( element );
+	const targetRect = new Rect( target );
+
+	let bestPosition;
+	let name;
+
+	// If there are no limits, just grab the very first position and be done with that drama.
+	if ( !limiter && !fitInViewport ) {
+		[ name, bestPosition ] = getPosition( positions[ 0 ], targetRect, elementRect );
+	} else {
+		const limiterRect = limiter && new Rect( limiter );
+		const viewportRect = fitInViewport && Rect.getViewportRect();
+
+		[ name, bestPosition ] =
+			getBestPosition( 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.
+			getPosition( positions[ 0 ], targetRect, elementRect );
+	}
+
+	let { left, top } = getAbsoluteRectCoordinates( bestPosition );
+
+	// (#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.
+	if ( positionedElementAncestor ) {
+		const ancestorPosition = getAbsoluteRectCoordinates( new Rect( positionedElementAncestor ) );
+
+		left -= ancestorPosition.left;
+		top -= ancestorPosition.top;
+	}
+
+	return { left, top, name };
+}
+
+// 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 getPosition( 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 {module:utils/dom/position~Options#positions} positions Functions returning
+// {@link module:utils/dom/position~Position} to be checked, in the order of preference.
+// @param {utils/dom/rect~Rect} targetRect A rect of the {@link module:utils/dom/position~Options#target}.
+// @param {utils/dom/rect~Rect} elementRect A rect of positioned {@link module:utils/dom/position~Options#element}.
+// @param {utils/dom/rect~Rect} limiterRect A rect of the {@link module:utils/dom/position~Options#limiter}.
+// @param {utils/dom/rect~Rect} viewportRect A rect of the viewport.
+// @returns {Array} An array containing the name of the position and it's rect.
+function getBestPosition( positions, targetRect, elementRect, limiterRect, viewportRect ) {
+	let maxLimiterIntersectArea = 0;
+	let maxViewportIntersectArea = 0;
+	let bestPositionRect;
+	let bestPositionName;
+
+	// This is when element is fully visible.
+	const elementRectArea = elementRect.getArea();
+
+	positions.some( position => {
+		const [ positionName, positionRect ] = getPosition( position, targetRect, elementRect );
+		let limiterIntersectArea;
+		let viewportIntersectArea;
+
+		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 = 0;
+				}
+			} else {
+				limiterIntersectArea = limiterRect.getIntersectionArea( positionRect );
+			}
+		}
+
+		if ( viewportRect ) {
+			viewportIntersectArea = viewportRect.getIntersectionArea( positionRect );
+		}
+
+		// The only criterion: intersection with the viewport.
+		if ( viewportRect && !limiterRect ) {
+			if ( viewportIntersectArea > maxViewportIntersectArea ) {
+				setBestPosition();
+			}
+		}
+		// The only criterion: intersection with the limiter.
+		else if ( !viewportRect && limiterRect ) {
+			if ( limiterIntersectArea > maxLimiterIntersectArea ) {
+				setBestPosition();
+			}
+		}
+		// Two criteria: intersection with the viewport and the limiter visible in the viewport.
+		else {
+			if ( viewportIntersectArea > maxViewportIntersectArea && limiterIntersectArea >= maxLimiterIntersectArea ) {
+				setBestPosition();
+			} else if ( viewportIntersectArea >= maxViewportIntersectArea && limiterIntersectArea > maxLimiterIntersectArea ) {
+				setBestPosition();
+			}
+		}
+
+		function setBestPosition() {
+			maxViewportIntersectArea = viewportIntersectArea;
+			maxLimiterIntersectArea = limiterIntersectArea;
+			bestPositionRect = positionRect;
+			bestPositionName = positionName;
+		}
+
+		// If a such position is found that element is fully container by the limiter then, obviously,
+		// there will be no better one, so finishing.
+		return limiterIntersectArea === elementRectArea;
+	} );
+
+	return bestPositionRect ? [ bestPositionName, bestPositionRect ] : null;
+}
+
+// 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 } ) {
+	return {
+		left: left + window.scrollX,
+		top: top + window.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} #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} #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.
+ */