From a53ec57b668cb1f6944a0f52f852ab8d4efbfda5 Mon Sep 17 00:00:00 2001
From: gwenn <gtreguier@gmail.com>
Date: Sun, 19 May 2019 10:17:11 +0200
Subject: [PATCH] Improve undo action

There is no need to temporarly remove the change listener.
Just use `try_borrow_mut`.
---
 src/lib.rs         |  3 ---
 src/line_buffer.rs | 26 ++++++++++++++++----------
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index f2dad47d04..5699d8f5b7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -515,7 +515,6 @@ fn readline_edit<H: Helper>(
                     kill_ring.kill(&text, Mode::Append)
                 }
             }
-            // TODO CTRL-_ // undo
             Cmd::AcceptLine => {
                 #[cfg(test)]
                 {
@@ -574,11 +573,9 @@ fn readline_edit<H: Helper>(
             }
             Cmd::Move(Movement::ViCharSearch(n, cs)) => s.edit_move_to(cs, n)?,
             Cmd::Undo(n) => {
-                s.line.remove_change_listener();
                 if s.changes.borrow_mut().undo(&mut s.line, n) {
                     s.refresh_line()?;
                 }
-                s.line.set_change_listener(s.changes.clone());
             }
             Cmd::Interrupt => {
                 return Err(error::ReadlineError::Interrupted);
diff --git a/src/line_buffer.rs b/src/line_buffer.rs
index a45dfffb39..5daeadf3d0 100644
--- a/src/line_buffer.rs
+++ b/src/line_buffer.rs
@@ -98,10 +98,6 @@ impl LineBuffer {
         self.cl = Some(dl);
     }
 
-    pub(crate) fn remove_change_listener(&mut self) {
-        self.cl = None;
-    }
-
     /// Extracts a string slice containing the entire buffer.
     pub fn as_str(&self) -> &str {
         &self.buf
@@ -201,7 +197,10 @@ impl LineBuffer {
         if n == 1 {
             self.buf.insert(self.pos, ch);
             for cl in &self.cl {
-                cl.borrow_mut().insert_char(self.pos, ch);
+                if let Ok(mut cl) = cl.try_borrow_mut() {
+                    cl.insert_char(self.pos, ch);
+                } // Ok: while undoing, cl is borrowed. And we want to ignore changes while
+                  // undoing.
             }
         } else {
             let text = iter::repeat(ch).take(n).collect::<String>();
@@ -644,8 +643,10 @@ impl LineBuffer {
     pub fn replace(&mut self, range: Range<usize>, text: &str) {
         let start = range.start;
         for cl in &self.cl {
-            cl.borrow_mut()
-                .replace(start, self.buf.index(range.clone()), text);
+            if let Ok(mut cl) = cl.try_borrow_mut() {
+                cl.replace(start, self.buf.index(range.clone()), text);
+            } // Ok: while undoing, cl is borrowed. And we want to ignore changes while
+              // undoing.
         }
         self.buf.drain(range);
         if start == self.buf.len() {
@@ -660,7 +661,10 @@ impl LineBuffer {
     /// Return `true` if the text has been inserted at the end of the line.
     pub fn insert_str(&mut self, idx: usize, s: &str) -> bool {
         for cl in &self.cl {
-            cl.borrow_mut().insert_str(idx, s);
+            if let Ok(mut cl) = cl.try_borrow_mut() {
+                cl.insert_str(idx, s);
+            } // Ok: while undoing, cl is borrowed. And we want to ignore changes while
+              // undoing.
         }
         if idx == self.buf.len() {
             self.buf.push_str(s);
@@ -685,8 +689,10 @@ impl LineBuffer {
             }
         }
         for cl in &self.cl {
-            cl.borrow_mut()
-                .delete(range.start, &self.buf[range.start..range.end], dir);
+            if let Ok(mut cl) = cl.try_borrow_mut() {
+                cl.delete(range.start, &self.buf[range.start..range.end], dir);
+            } // Ok: while undoing, cl is borrowed. And we want to ignore changes while
+              // undoing.
         }
         self.buf.drain(range)
     }