Optionally use native 'beforeinput' events instead of React's synthetic event

src/component/base/DraftEditor.react.js

@@ -42,6 +42,7 @@ const editOnSelect = require('editOnSelect');
 const getScrollPosition = require('getScrollPosition');
 const invariant = require('invariant');
 const nullthrows = require('nullthrows');
+const areLevel2InputEventsSupported = require('areLevel2InputEventsSupported');
 
 const isIE = UserAgent.isBrowser('IE');
 
@@ -96,6 +97,7 @@ class DraftEditor extends React.Component {
   _renderNativeContent: boolean;
   _updatedNativeInsertionBlock: boolean;
   _latestCommittedEditorState: EditorState;
+  _useNativeBeforeInput: boolean;
 
   /**
    * Define proxies that can route events to the current handler.
@@ -136,6 +138,8 @@ class DraftEditor extends React.Component {
   constructor(props: DraftEditorProps) {
     super(props);
 
+    this._useNativeBeforeInput = props.useNativeBeforeInputIfAble && areLevel2InputEventsSupported();
+
     this._blockSelectEvents = false;
     this._clipboard = null;
     this._handler = null;
@@ -235,15 +239,28 @@ class DraftEditor extends React.Component {
     // it is not possible to set up an onPaste handler through react.
     // Manually use addEventListener and removeEventListener below.
     // See the comments in editOnPaste for why this is needed.
+    //
+    // We also provide an option to manually manage our own onBeforeInput handler
+    // without going through React. React polyfills this event using `textInput`/`keypress`,
+    // but doesn't use the natively-available event when it can (see https://github.com/facebook/react/issues/11211)
+    // In rare circumstances, we want to provide the option to force the use of the native
+    // `beforeinput`, event. Slate does something similar https://github.com/ianstormtaylor/slate/commit/f812816b7dcb2d4b2efa0d4ba12d4feac31850c9
     if (this._editor) {
       const editorNode = ReactDOM.findDOMNode(this._editor);
       editorNode.removeEventListener('paste', this._onPaste);
+      if (this._useNativeBeforeInput) {
+        editorNode.removeEventListener('beforeinput', this._onBeforeInput);
+      }
     }
 
     this._editor = ref;
     if (this._editor) {
       const editorNode = ReactDOM.findDOMNode(this._editor);
+
       editorNode.addEventListener('paste', this._onPaste);
+      if (this._useNativeBeforeInput) {
+        editorNode.addEventListener('beforeinput', this._onBeforeInput);
+      }
 
       // Add ignore attribute for an IESpell, an obscure plugin that doesn't respect spellcheck="false" on a
       // contenteditable div
@@ -307,7 +324,7 @@ class DraftEditor extends React.Component {
             })}
             contentEditable={!readOnly}
             data-testid={this.props.webDriverTestID}
-            onBeforeInput={this._onBeforeInput}
+            onBeforeInput={this._useNativeBeforeInput ? undefined : this._onBeforeInput}
             onBlur={this._onBlur}
             onCompositionEnd={this._onCompositionEnd}
             onCompositionStart={this._onCompositionStart}

src/component/base/DraftEditorProps.js

@@ -175,6 +175,8 @@ export type DraftEditorProps = {
   // an element tag and an optional react element wrapper. This configuration
   // is used for both rendering and paste processing.
   blockRenderMap: DraftBlockRenderMap,
+
+  useNativeBeforeInputIfAble?: boolean,
 };
 
 export type DraftEditorDefaultProps = {
@@ -185,4 +187,5 @@ export type DraftEditorDefaultProps = {
   readOnly: boolean,
   spellCheck: boolean,
   stripPastedStyles: boolean,
+  useNativeBeforeInputIfAble: false,
 };

src/component/handlers/edit/editOnBeforeInput.js

@@ -78,7 +78,7 @@ function replaceText(
  * preserve spellcheck highlighting, which disappears or flashes if re-render
  * occurs on the relevant text nodes.
  */
-function editOnBeforeInput(editor: DraftEditor, e: SyntheticInputEvent): void {
+function editOnBeforeInput(editor: DraftEditor, e: InputEvent | SyntheticInputEvent): void {
 
   // React doesn't fire a selection event until mouseUp, so it's possible to
   // click to change selection, hold the mouse down, and type a character

src/component/utils/areLevel2InputEventsSupported.js

@@ -0,0 +1,21 @@
+/**
+ * @providesModule areLevel2InputEventsSupported
+ * @typechecks
+ * @flow
+ * 
+ * This method determines if we're in a browser which fires native 'beforeinput'
+ * events (Level 1 support) and allows that event to be cancellable (Level 2 support)
+ * 
+ * It's borrowed from Slate https://github.com/ianstormtaylor/slate/blob/9694b228464d8b4d874074496a4c0a50f6ec4614/packages/slate-dev-environment/src/index.js#L74-L79
+ */
+
+'use strict';
+
+function areLevel2InputEventsSupported(): boolean {
+  const element = window.document.createElement('div');
+  element.contentEditable = true;
+  const support = 'onbeforeinput' in element;
+  return support;
+}
+
+module.exports = areLevel2InputEventsSupported;