From dc9694c42cde3d61d13370ce49a03404727f3bd4 Mon Sep 17 00:00:00 2001
From: iseulde <wp@iseulde.com>
Date: Tue, 26 Mar 2019 10:51:06 +0100
Subject: [PATCH] Merge isEdge logic

---
 packages/dom/src/dom.js | 115 ++++++++++++++--------------------------
 1 file changed, 40 insertions(+), 75 deletions(-)

diff --git a/packages/dom/src/dom.js b/packages/dom/src/dom.js
index fadf4d135b11d1..d0034205ba86a9 100644
--- a/packages/dom/src/dom.js
+++ b/packages/dom/src/dom.js
@@ -60,14 +60,17 @@ function isSelectionForward( selection ) {
 }
 
 /**
- * Check whether the selection is horizontally at the edge of the container.
+ * Check whether the selection is at the edge of the container. Checks for
+ * horizontal position by default. Set `isVertical` to true to check only
+ * vertically.
  *
- * @param {Element} container Focusable element.
- * @param {boolean} isReverse Set to true to check left, false for right.
+ * @param {Element} container  Focusable element.
+ * @param {boolean} isReverse  Set to true to check left, false to check right.
+ * @param {boolean} isVertical Set to true to check only vertical position.
  *
  * @return {boolean} True if at the horizontal edge, false if not.
  */
-export function isHorizontalEdge( container, isReverse ) {
+function isEdge( container, { isReverse, isVertical } ) {
 	if ( includes( [ 'INPUT', 'TEXTAREA' ], container.tagName ) ) {
 		if ( container.selectionStart !== container.selectionEnd ) {
 			return false;
@@ -86,36 +89,35 @@ export function isHorizontalEdge( container, isReverse ) {
 
 	const selection = window.getSelection();
 
-	// Only consider the selection at the edge if the direction is towards the
-	// edge.
-	if (
-		! selection.isCollapsed &&
-		isSelectionForward( selection ) === isReverse
-	) {
-		return false;
+	if ( ! selection.rangeCount ) {
+		return;
 	}
 
-	const range = selection.rangeCount ? selection.getRangeAt( 0 ) : null;
+	const rangeRect = getRectangleFromRange( selection.getRangeAt( 0 ) );
 
-	if ( ! range ) {
+	if ( ! rangeRect ) {
 		return false;
 	}
 
-	const rangeRect = getRectangleFromRange( range );
+	const computedStyle = window.getComputedStyle( container );
+	const lineHeight = parseInt( computedStyle.lineHeight, 10 );
 
-	if ( ! rangeRect ) {
+	// Only consider the multiline selection at the edge if the direction is
+	// towards the edge.
+	if (
+		! selection.isCollapsed &&
+		rangeRect.height > lineHeight &&
+		isSelectionForward( selection ) === isReverse
+	) {
 		return false;
 	}
 
-	const containerRect = container.getBoundingClientRect();
-
 	// Calculate a buffer that is half the line height. In some browsers, the
 	// selection rectangle may not fill the entire height of the line, so we add
-	// half the line height to the selection rectangle to ensure that it is well
+	// 3/4 the line height to the selection rectangle to ensure that it is well
 	// over its line boundary.
-	const { lineHeight } = window.getComputedStyle( container );
 	const buffer = 3 * parseInt( lineHeight, 10 ) / 4;
-
+	const containerRect = container.getBoundingClientRect();
 	const verticalEdge = isReverse ?
 		containerRect.top > rangeRect.top - buffer :
 		containerRect.bottom < rangeRect.bottom + buffer;
@@ -124,10 +126,12 @@ export function isHorizontalEdge( container, isReverse ) {
 		return false;
 	}
 
+	if ( isVertical ) {
+		return true;
+	}
+
 	const x = isReverse ? containerRect.left + 1 : containerRect.right - 1;
-	const y = isReverse ?
-		containerRect.top + buffer :
-		containerRect.bottom - buffer;
+	const y = isReverse ? containerRect.top + buffer : containerRect.bottom - buffer;
 	const testRange = hiddenCaretRangeFromPoint( document, x, y, container );
 
 	if ( ! testRange ) {
@@ -140,6 +144,18 @@ export function isHorizontalEdge( container, isReverse ) {
 	return Math.round( testRect[ side ] ) === Math.round( rangeRect[ side ] );
 }
 
+/**
+ * Check whether the selection is horizontally at the edge of the container.
+ *
+ * @param {Element} container Focusable element.
+ * @param {boolean} isReverse Set to true to check left, false for right.
+ *
+ * @return {boolean} True if at the horizontal edge, false if not.
+ */
+export function isHorizontalEdge( container, isReverse ) {
+	return isEdge( container, { isReverse } );
+}
+
 /**
  * Check whether the selection is vertically at the edge of the container.
  *
@@ -149,58 +165,7 @@ export function isHorizontalEdge( container, isReverse ) {
  * @return {boolean} True if at the edge, false if not.
  */
 export function isVerticalEdge( container, isReverse ) {
-	if ( includes( [ 'INPUT', 'TEXTAREA' ], container.tagName ) ) {
-		return isHorizontalEdge( container, isReverse );
-	}
-
-	if ( ! container.isContentEditable ) {
-		return true;
-	}
-
-	const selection = window.getSelection();
-	const range = selection.rangeCount ? selection.getRangeAt( 0 ) : null;
-
-	if ( ! range ) {
-		return false;
-	}
-
-	const rangeRect = getRectangleFromRange( range );
-
-	if ( ! rangeRect ) {
-		return false;
-	}
-
-	// Calculate a buffer that is half the line height. In some browsers, the
-	// selection rectangle may not fill the entire height of the line, so we add
-	// half the line height to the selection rectangle to ensure that it is well
-	// over its line boundary.
-	const computedStyle = window.getComputedStyle( container );
-	const lineHeight = parseInt( computedStyle.lineHeight, 10 );
-
-	// Only consider the multiline selection at the edge if the direction is
-	// towards the edge.
-	if (
-		! selection.isCollapsed &&
-		rangeRect.height > lineHeight &&
-		isSelectionForward( selection ) === isReverse
-	) {
-		return false;
-	}
-
-	const editableRect = container.getBoundingClientRect();
-	const buffer = lineHeight / 2;
-
-	// Too low.
-	if ( isReverse && rangeRect.top - buffer > editableRect.top ) {
-		return false;
-	}
-
-	// Too high.
-	if ( ! isReverse && rangeRect.bottom + buffer < editableRect.bottom ) {
-		return false;
-	}
-
-	return true;
+	return isEdge( container, { isReverse, isVertical: true } );
 }
 
 /**