From f0190320333c8a8f5f5520833d754ada1ce0f529 Mon Sep 17 00:00:00 2001
From: rustbasic <127506429+rustbasic@users.noreply.github.com>
Date: Tue, 12 Mar 2024 19:21:33 +0900
Subject: [PATCH] TextEdit: fix crash when hitting SHIFT + TAB around non-ASCII
 text (#3984)

* Closes #3846
* Closes #3878

Dear emilk.

Leaving aside other function,
I think this is all you need to fix to patch the panic that occurs when
Shift + TAB.

Thank you, emilk.
---
 crates/egui/src/widgets/text_edit/text_buffer.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crates/egui/src/widgets/text_edit/text_buffer.rs b/crates/egui/src/widgets/text_edit/text_buffer.rs
index f28878a1..e70ce695 100644
--- a/crates/egui/src/widgets/text_edit/text_buffer.rs
+++ b/crates/egui/src/widgets/text_edit/text_buffer.rs
@@ -89,10 +89,12 @@ pub trait TextBuffer {
     fn decrease_indentation(&mut self, ccursor: &mut CCursor) {
         let line_start = find_line_start(self.as_str(), *ccursor);
 
-        let remove_len = if self.as_str()[line_start.index..].starts_with('\t') {
+        let remove_len = if self.as_str().chars().nth(line_start.index) == Some('\t') {
             Some(1)
-        } else if self.as_str()[line_start.index..]
+        } else if self
+            .as_str()
             .chars()
+            .skip(line_start.index)
             .take(TAB_SIZE)
             .all(|c| c == ' ')
         {