From 2512df98712ca954f44d8913e5145dff1751e120 Mon Sep 17 00:00:00 2001
From: Andrew Duthie <andrew@andrewduthie.com>
Date: Fri, 11 May 2018 11:22:52 -0400
Subject: [PATCH] Writing Flow: Consider horizontal handled by stopPropagation
 in RichText

---
 editor/components/rich-text/index.js | 77 +++++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 7 deletions(-)

diff --git a/editor/components/rich-text/index.js b/editor/components/rich-text/index.js
index cd2488cd919f47..634d187353b82a 100644
--- a/editor/components/rich-text/index.js
+++ b/editor/components/rich-text/index.js
@@ -45,7 +45,27 @@ import { EVENTS } from './constants';
 import { withBlockEditContext } from '../block-edit/context';
 import { domToFormat, valueToString } from './format';
 
-const { BACKSPACE, DELETE, ENTER, rawShortcut } = keycodes;
+/**
+ * Browser dependencies
+ */
+
+const { Node } = window;
+
+/**
+ * Module constants
+ */
+
+const { LEFT, RIGHT, BACKSPACE, DELETE, ENTER, rawShortcut } = keycodes;
+
+/**
+ * Zero-width space character used by TinyMCE as a caret landing point for
+ * inline boundary nodes.
+ *
+ * @see tinymce/src/core/main/ts/text/Zwsp.ts
+ *
+ * @type {string}
+ */
+const TINYMCE_ZWSP = '\uFEFF';
 
 /**
  * Returns true if the node is the inline node boundary. This is used in node
@@ -61,7 +81,7 @@ const { BACKSPACE, DELETE, ENTER, rawShortcut } = keycodes;
  */
 export function isEmptyInlineBoundary( node ) {
 	const text = node.nodeName === 'A' ? node.innerText : node.textContent;
-	return text === '\uFEFF';
+	return text === TINYMCE_ZWSP;
 }
 
 /**
@@ -114,6 +134,7 @@ export class RichText extends Component {
 		this.onChange = this.onChange.bind( this );
 		this.onNewBlock = this.onNewBlock.bind( this );
 		this.onNodeChange = this.onNodeChange.bind( this );
+		this.onHorizontalNavigationKeyDown = this.onHorizontalNavigationKeyDown.bind( this );
 		this.onKeyDown = this.onKeyDown.bind( this );
 		this.onKeyUp = this.onKeyUp.bind( this );
 		this.changeFormats = this.changeFormats.bind( this );
@@ -438,19 +459,56 @@ export class RichText extends Component {
 			left: position.left - containerPosition.left + ( position.width / 2 ) + toolbarOffset.left,
 		};
 	}
+	/**
+	 * Handles a horizontal navigation key down event to stop propagation if it
+	 * can be inferred that it will be handled by TinyMCE (notably transitions
+	 * out of an inline boundary node).
+	 *
+	 * @param {KeyboardEvent} event Keydown event.
+	 */
+	onHorizontalNavigationKeyDown( event ) {
+		const { focusNode, focusOffset } = window.getSelection();
+		const { nodeType, nodeValue } = focusNode;
+
+		if ( nodeType !== Node.TEXT_NODE ) {
+			return;
+		}
+
+		const isReverse = event.keyCode === LEFT;
+
+		let offset = focusOffset;
+		if ( isReverse ) {
+			offset--;
+		}
+
+		// [WORKAROUND]: When in a new paragraph in a new inline boundary node,
+		// while typing the zero-width space occurs as the first child instead
+		// of at the end of the inline boundary where the caret is. This should
+		// only be exempt when focusNode is not _only_ the ZWSP, which occurs
+		// when caret is placed on the right outside edge of inline boundary.
+		if ( ! isReverse && focusOffset === nodeValue.length &&
+				nodeValue.length > 1 && nodeValue[ 0 ] === TINYMCE_ZWSP ) {
+			offset = 0;
+		}
+
+		if ( nodeValue[ offset ] === TINYMCE_ZWSP ) {
+			event.stopPropagation();
+		}
+	}
 
 	/**
 	 * Handles a keydown event from tinyMCE.
 	 *
-	 * @param {KeydownEvent} event The keydow event as triggered by tinyMCE.
+	 * @param {KeyboardEvent} event Keydown event.
 	 */
 	onKeyDown( event ) {
 		const dom = this.editor.dom;
 		const rootNode = this.editor.getBody();
+		const { keyCode } = event;
 
 		if (
-			( event.keyCode === BACKSPACE && isHorizontalEdge( rootNode, true ) ) ||
-			( event.keyCode === DELETE && isHorizontalEdge( rootNode, false ) )
+			( keyCode === BACKSPACE && isHorizontalEdge( rootNode, true ) ) ||
+			( keyCode === DELETE && isHorizontalEdge( rootNode, false ) )
 		) {
 			if ( ! this.props.onMerge && ! this.props.onRemove ) {
 				return;
@@ -458,7 +516,7 @@ export class RichText extends Component {
 
 			this.onCreateUndoLevel();
 
-			const forward = event.keyCode === DELETE;
+			const forward = keyCode === DELETE;
 
 			if ( this.props.onMerge ) {
 				this.props.onMerge( forward );
@@ -476,9 +534,14 @@ export class RichText extends Component {
 			event.stopImmediatePropagation();
 		}
 
+		const isHorizontalNavigation = keyCode === LEFT || keyCode === RIGHT;
+		if ( isHorizontalNavigation ) {
+			this.onHorizontalNavigationKeyDown( event );
+		}
+
 		// If we click shift+Enter on inline RichTexts, we avoid creating two contenteditables
 		// We also split the content and call the onSplit prop if provided.
-		if ( event.keyCode === ENTER ) {
+		if ( keyCode === ENTER ) {
 			if ( this.props.multiline ) {
 				if ( ! this.props.onSplit ) {
 					return;