fix: preserve alt backspace in panes (#165)

refs #155

Co-authored-by: kangal-bot <kangal-bot@users.noreply.github.com>

src/app/input/terminal.rs

@@ -486,6 +486,33 @@ mod tests {
         assert_eq!(app.state.mode, Mode::Terminal);
     }
 
+    #[tokio::test]
+    async fn alt_backspace_is_forwarded_to_focused_pane() {
+        let mut app = app_for_mouse_test();
+        let mut ws = Workspace::test_new("test");
+        let pane_id = ws.tabs[0].root_pane;
+        let pane_infos = ws.tabs[0].layout.panes(Rect::new(0, 0, 80, 24));
+        let info = pane_infos[0].clone();
+        let (runtime, mut rx) = crate::pane::PaneRuntime::test_with_channel(
+            info.inner_rect.width,
+            info.inner_rect.height,
+        );
+        ws.tabs[0].runtimes.insert(pane_id, runtime);
+
+        app.state.workspaces = vec![ws];
+        app.state.active = Some(0);
+        app.state.selected = 0;
+        app.state.mode = Mode::Terminal;
+        app.state.view.pane_infos = pane_infos;
+
+        let key = crate::input::parse_terminal_key_sequence("\x1b\x7f").unwrap();
+        app.handle_terminal_key_headless(key);
+
+        let bytes = rx.try_recv().unwrap();
+        assert_eq!(bytes.as_ref(), b"\x1b\x7f");
+        assert!(rx.try_recv().is_err());
+    }
+
     #[tokio::test]
     async fn page_up_scrolls_plain_shell_pane() {
         let mut app = app_for_mouse_test();

src/input/encode.rs

@@ -523,6 +523,12 @@ mod tests {
         assert_eq!(encode_key(key, KeyboardProtocol::Legacy), b"\x1ba");
     }
 
+    #[test]
+    fn legacy_alt_backspace_sends_escape_delete() {
+        let key = KeyEvent::new(KeyCode::Backspace, KeyModifiers::ALT);
+        assert_eq!(encode_key(key, KeyboardProtocol::Legacy), b"\x1b\x7f");
+    }
+
     #[test]
     fn application_cursor_keys_use_ss3_sequences() {
         assert_eq!(encode_cursor_key(KeyCode::Up, true), b"\x1bOA");
@@ -638,6 +644,15 @@ mod tests {
         );
     }
 
+    #[test]
+    fn kitty_alt_backspace_uses_csi_u() {
+        let key = KeyEvent::new(KeyCode::Backspace, KeyModifiers::ALT);
+        assert_eq!(
+            encode_key(key, KeyboardProtocol::Kitty { flags: 1 }),
+            b"\x1b[127;3u"
+        );
+    }
+
     #[test]
     fn kitty_plain_ctrl_c_uses_csi_u() {
         let key = KeyEvent::new(KeyCode::Char('c'), KeyModifiers::CONTROL);

src/input/parse.rs

@@ -67,6 +67,7 @@ fn parse_legacy_key_sequence(data: &str) -> Option<TerminalKey> {
         "\r" => Some(TerminalKey::new(KeyCode::Enter, KeyModifiers::empty())),
         "\t" => Some(TerminalKey::new(KeyCode::Tab, KeyModifiers::empty())),
         "\x1b" => Some(TerminalKey::new(KeyCode::Esc, KeyModifiers::empty())),
+        "\x1b\x7f" => Some(TerminalKey::new(KeyCode::Backspace, KeyModifiers::ALT)),
         "\x7f" => Some(TerminalKey::new(KeyCode::Backspace, KeyModifiers::empty())),
         _ if data.starts_with('\x1b') => {
             let rest = data.strip_prefix('\x1b')?;
@@ -441,6 +442,15 @@ mod tests {
         assert_eq!(key.shifted_codepoint, Some('L' as u32));
     }
 
+    #[test]
+    fn parse_kitty_alt_backspace_sequence() {
+        let key = parse_terminal_key_sequence("\x1b[127;3u").unwrap();
+        assert_eq!(key.code, KeyCode::Backspace);
+        assert_eq!(key.modifiers, KeyModifiers::ALT);
+        assert_eq!(key.kind, crossterm::event::KeyEventKind::Press);
+        assert_eq!(key.shifted_codepoint, None);
+    }
+
     #[test]
     fn parse_modify_other_keys_sequence() {
         let key = parse_terminal_key_sequence("\x1b[27;6;108~").unwrap();
@@ -464,6 +474,13 @@ mod tests {
         assert_eq!(key.modifiers, KeyModifiers::empty());
     }
 
+    #[test]
+    fn parse_legacy_alt_backspace_sequence() {
+        let key = parse_terminal_key_sequence("\x1b\x7f").unwrap();
+        assert_eq!(key.code, KeyCode::Backspace);
+        assert_eq!(key.modifiers, KeyModifiers::ALT);
+    }
+
     #[test]
     fn parse_kitty_modifier_sequence() {
         let key = parse_terminal_key_sequence("\x1b[57441;2:1u").unwrap();

src/pane/terminal.rs

@@ -1502,6 +1502,20 @@ mod tests {
         assert_eq!(after, b"\x1b[13;6u");
     }
 
+    #[test]
+    fn ghostty_kitty_pane_encodes_parsed_legacy_alt_backspace_as_csi_u() {
+        let (tx, _rx) = mpsc::channel(4);
+        let terminal = crate::ghostty::Terminal::new(80, 24, 0).unwrap();
+        let pane = GhosttyPaneTerminal::new(terminal, tx.clone()).unwrap();
+        let pane_id = PaneId::from_raw(1);
+        pane.process_pty_bytes(pane_id, 0, b"\x1b[>1u", &tx);
+
+        let key = crate::input::parse_terminal_key_sequence("\x1b\x7f").unwrap();
+        let encoded = pane.encode_terminal_key(key, crate::input::KeyboardProtocol::Legacy);
+
+        assert_eq!(encoded, b"\x1b[127;3u");
+    }
+
     #[test]
     fn ghostty_key_encoders_are_isolated_per_pane() {
         let (tx, _rx) = mpsc::channel(4);

src/raw_input.rs

@@ -673,6 +673,26 @@ mod tests {
         assert_eq!(key.modifiers, KeyModifiers::ALT);
     }
 
+    #[test]
+    fn parses_legacy_alt_backspace() {
+        let (RawInputEvent::Key(key), consumed) = extract_one_event(b"\x1b\x7f").unwrap() else {
+            panic!("expected key");
+        };
+        assert_eq!(consumed, 2);
+        assert_eq!(key.code, KeyCode::Backspace);
+        assert_eq!(key.modifiers, KeyModifiers::ALT);
+    }
+
+    #[test]
+    fn parses_kitty_alt_backspace() {
+        let (RawInputEvent::Key(key), consumed) = extract_one_event(b"\x1b[127;3u").unwrap() else {
+            panic!("expected key");
+        };
+        assert_eq!(consumed, 8);
+        assert_eq!(key.code, KeyCode::Backspace);
+        assert_eq!(key.modifiers, KeyModifiers::ALT);
+    }
+
     #[test]
     fn parses_enhanced_pageup_press() {
         let (RawInputEvent::Key(key), consumed) = extract_one_event(b"\x1b[5;1:1~").unwrap() else {
@@ -704,6 +724,8 @@ mod tests {
             (b"\x7f", KeyCode::Backspace, KeyModifiers::empty()),
             (b"\x1b[A", KeyCode::Up, KeyModifiers::empty()),
             (b"\x1b[1;3A", KeyCode::Up, KeyModifiers::ALT),
+            (b"\x1b\x7f", KeyCode::Backspace, KeyModifiers::ALT),
+            (b"\x1b[127;3u", KeyCode::Backspace, KeyModifiers::ALT),
             (b"\x1b[57420;1u", KeyCode::Down, KeyModifiers::empty()),
             (b"\x1b[57423;1u", KeyCode::Home, KeyModifiers::empty()),
             (b"\x1b[49:33;2:1u", KeyCode::Char('1'), KeyModifiers::SHIFT),

tests/fixtures/keyboard_protocol_corpus.tsv

@@ -4,6 +4,7 @@ legacy_ctrl_z	1a	char:z	control	press
 legacy_enter	0d	enter	-	press	
 legacy_tab	09	tab	-	press	
 legacy_backspace	7f	backspace	-	press	
+legacy_alt_backspace	1b7f	backspace	alt	press
 legacy_up	1b5b41	up	-	press	
 legacy_home	1b5b48	home	-	press	
 xterm_alt_up	1b5b313b3341	up	alt	press	
@@ -12,6 +13,7 @@ xterm_shift_pageup	1b5b353b327e	pageup	shift	press
 ghostty_enhanced_up_press	1b5b313b313a3141	up	-	press	
 ghostty_enhanced_up_release	1b5b313b313a3341	up	-	release	
 modify_other_keys_ctrl_shift_l	1b5b32373b363b3130387e	char:l	control+shift	press	
+kitty_alt_backspace	1b5b3132373b3375	backspace	alt	press
 kitty_shift_letter	1b5b3130383a37363b323a3175	char:l	shift	press	76
 kitty_shift_symbol	1b5b34393a33333b323a3175	char:1	shift	press	33
 kitty_release_letter	1b5b3130383a37363b323a3375	char:l	shift	release	76

tests/fixtures/macos_terminal_variants.tsv

@@ -1,13 +1,16 @@
 # source	key	bytes_hex	code	modifiers	kind	shifted_codepoint
+ghostty-macos	alt+backspace	1b7f	backspace	alt	press
 iterm2-macos	alt+up	1b5b313b3341	up	alt	press	
 iterm2-macos	alt+down	1b5b313b3342	down	alt	press	
 iterm2-macos	alt+left	1b62	char:b	alt	press	
 iterm2-macos	alt+right	1b66	char:f	alt	press	
+iterm2-macos	alt+backspace	1b7f	backspace	alt	press
 iterm2-macos	shift+enter	0d	enter	-	press	
 terminal-app-macos	alt+up	1b1b5b41	up	alt	press	
 terminal-app-macos	alt+down	1b1b5b42	down	alt	press	
 terminal-app-macos	alt+left	1b62	char:b	alt	press	
 terminal-app-macos	alt+right	1b66	char:f	alt	press	
+terminal-app-macos	alt+backspace	1b7f	backspace	alt	press
 terminal-app-macos	shift+enter	0d	enter	-	press	
 terminal-app-tmux	alt+up	1b1b5b41	up	alt	press	
 terminal-app-tmux	alt+down	1b1b5b42	down	alt	press