fix(textarea): clamp undo/redo cursor after oversized delete_str (#9)

CHANGELOG.md

@@ -1,3 +1,13 @@
+<a id="v0.9.1"></a>
+# [v0.9.1](https://github.com/srothgan/tui-textarea/releases/tag/v0.9.1) - 2026-02-18
+
+- Fix panic on `Ctrl+U`/`undo()` after oversized `delete_str()` (including `select_all() + delete_str(usize::MAX)` on empty buffers).
+- Fix root cause by clamping exhausted `delete_str()` ranges to EOF so history never stores out-of-bounds rows.
+- Add defensive cursor clamping in `undo()`/`redo()` when restoring from history.
+- Add regression tests for the reported panic paths and invalid-history cursor restore edge cases.
+
+[Changes][v0.9.1]
+
 <a id="v0.9.0"></a>
 # [v0.9.0](https://github.com/srothgan/tui-textarea/releases/tag/v0.9.0) - 2026-02-18
 
@@ -474,6 +484,7 @@ First release :tada:
 
 [Changes][v0.1.0]
 
+[v0.9.1]: https://github.com/srothgan/tui-textarea/compare/v0.9.0...v0.9.1
 [v0.9.0]: https://github.com/srothgan/tui-textarea/compare/v0.8.0...v0.9.0
 [v0.8.0]: https://github.com/srothgan/tui-textarea/compare/v0.7.1...v0.8.0
 [v0.7.1]: https://github.com/srothgan/tui-textarea/compare/v0.7.0...v0.7.1

Cargo.toml

@@ -3,7 +3,7 @@ name = "tui-textarea-2"
 homepage = "https://github.com/srothgan/tui-textarea#readme"
 repository = "https://github.com/srothgan/tui-textarea"
 documentation = "https://docs.rs/tui-textarea-2/latest/tui_textarea/"
-version = "0.9.0"
+version = "0.9.1"
 edition = "2021"
 rust-version = "1.56.1" # for `tui` crate support
 authors = ["Simon Peter Rothgang <simonrothgang@icloud.com>", "rhysd <lin90162@yahoo.co.jp>"]

src/textarea.rs

@@ -998,6 +998,14 @@ impl<'a> TextArea<'a> {
             r += 1;
         }
 
+        if r == self.lines.len() {
+            // Clamp exhausted deletions to EOF on the last line so history keeps a valid cursor.
+            r = self.lines.len() - 1;
+            let line = &self.lines[r];
+            offset = line.len();
+            col = line.chars().count();
+        }
+
         let start = Pos::new(start_row, start_col, start_offset);
         let end = Pos::new(r, col, offset);
         self.delete_range(start, end, true);
@@ -1465,6 +1473,18 @@ impl<'a> TextArea<'a> {
             .unwrap_or(line.len())
     }
 
+    fn clamp_cursor_to_buffer(&mut self, cursor: (usize, usize)) -> (usize, usize) {
+        if self.lines.is_empty() {
+            self.lines.push(String::new());
+            return (0, 0);
+        }
+
+        let (row, col) = cursor;
+        let row = row.min(self.lines.len() - 1);
+        let col = col.min(self.lines[row].chars().count());
+        (row, col)
+    }
+
     /// Set the style used for text selection. The default style is light blue.
     /// ```
     /// use tui_textarea::TextArea;
@@ -1651,7 +1671,7 @@ impl<'a> TextArea<'a> {
     pub fn undo(&mut self) -> bool {
         if let Some(cursor) = self.history.undo(&mut self.lines) {
             self.cancel_selection();
-            self.cursor = cursor;
+            self.cursor = self.clamp_cursor_to_buffer(cursor);
             true
         } else {
             false
@@ -1674,7 +1694,7 @@ impl<'a> TextArea<'a> {
     pub fn redo(&mut self) -> bool {
         if let Some(cursor) = self.history.redo(&mut self.lines) {
             self.cancel_selection();
-            self.cursor = cursor;
+            self.cursor = self.clamp_cursor_to_buffer(cursor);
             true
         } else {
             false
@@ -2639,4 +2659,33 @@ mod tests {
         textarea.scroll((-5, 0));
         assert_eq!(textarea.cursor(), (12, 0));
     }
+
+    #[test]
+    fn undo_clamps_invalid_cursor_from_history() {
+        let mut textarea = TextArea::default();
+        textarea.history.push(Edit::new(
+            EditKind::DeleteStr(String::new()),
+            Pos::new(1, 10, 0),
+            Pos::new(0, 0, 0),
+        ));
+
+        assert!(textarea.undo());
+        assert_eq!(textarea.lines(), [""]);
+        assert_eq!(textarea.cursor(), (0, 0));
+    }
+
+    #[test]
+    fn redo_clamps_invalid_cursor_from_history() {
+        let mut textarea = TextArea::default();
+        textarea.history.push(Edit::new(
+            EditKind::InsertStr(String::new()),
+            Pos::new(0, 0, 0),
+            Pos::new(1, 10, 0),
+        ));
+
+        assert!(textarea.undo());
+        assert!(textarea.redo());
+        assert_eq!(textarea.lines(), [""]);
+        assert_eq!(textarea.cursor(), (0, 0));
+    }
 }

tests/input.rs

@@ -80,3 +80,38 @@ fn test_insert_multi_code_unit_emoji() {
     }
     assert_eq!(t.lines(), ["👨‍👩‍👧‍👦"]);
 }
+
+#[test]
+fn test_ctrl_u_after_delete_str_max_on_empty_buffer() {
+    let mut t = TextArea::default();
+    assert!(t.delete_str(usize::MAX));
+    assert_eq!(t.lines(), [""]);
+    assert_eq!(t.cursor(), (0, 0));
+
+    assert!(t.input(Input {
+        key: Key::Char('u'),
+        ctrl: true,
+        alt: false,
+        shift: false,
+    }));
+    assert_eq!(t.lines(), [""]);
+    assert_eq!(t.cursor(), (0, 0));
+}
+
+#[test]
+fn test_ctrl_u_after_select_all_then_delete_str_max_on_empty_buffer() {
+    let mut t = TextArea::default();
+    t.select_all();
+    assert!(t.delete_str(usize::MAX));
+    assert_eq!(t.lines(), [""]);
+    assert_eq!(t.cursor(), (0, 0));
+
+    assert!(t.input(Input {
+        key: Key::Char('u'),
+        ctrl: true,
+        alt: false,
+        shift: false,
+    }));
+    assert_eq!(t.lines(), [""]);
+    assert_eq!(t.cursor(), (0, 0));
+}