RichText: ignore selection changes during composition (#16960)

packages/rich-text/src/component/index.js

@@ -391,9 +391,11 @@ class RichText extends Component {
 	}
 
 	/**
-	 * Handles the `selectionchange` event: sync the selection to local state.
+	 * Syncs the selection to local state. A callback for the `selectionchange`
+	 * native events, `keyup`, `mouseup` and `touchend` synthetic events, and
+	 * animation frames after the `focus` event.
 	 *
-	 * @param {Event} event `selectionchange` event.
+	 * @param {Event|SyntheticEvent|DOMHighResTimeStamp} event
 	 */
 	onSelectionChange( event ) {
 		if (
@@ -403,6 +405,15 @@ class RichText extends Component {
 			return;
 		}
 
+		// In case of a keyboard event, ignore selection changes during
+		// composition.
+		if (
+			event.nativeEvent &&
+			event.nativeEvent.isComposing
+		) {
+			return;
+		}
+
 		const { start, end } = this.createRecord();
 		const value = this.getRecord();