From 27ed93970fab1f0fd0c01cef5b1cb2c0a361aab2 Mon Sep 17 00:00:00 2001
From: singerdmx <singerdmx@gmail.com>
Date: Tue, 29 Dec 2020 15:06:37 -0800
Subject: [PATCH] Fix Undo throw Offset cannot be negative

---
 lib/widgets/controller.dart | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/widgets/controller.dart b/lib/widgets/controller.dart
index 83a27bbc..4bfc5a4f 100644
--- a/lib/widgets/controller.dart
+++ b/lib/widgets/controller.dart
@@ -44,13 +44,23 @@ class QuillController extends ChangeNotifier {
 
   void undo() {
     if (document.undo()) {
-      notifyListeners();
+      if (this.selection.extentOffset >= document.length) {
+        updateSelection(TextSelection.collapsed(offset: document.length),
+            ChangeSource.LOCAL);
+      } else {
+        notifyListeners();
+      }
     }
   }
 
   void redo() {
     if (document.redo()) {
-      notifyListeners();
+      if (this.selection.extentOffset >= document.length) {
+        updateSelection(TextSelection.collapsed(offset: document.length),
+            ChangeSource.LOCAL);
+      } else {
+        notifyListeners();
+      }
     }
   }