Add support for in-band window resize notifications

Fixes #7642

docs/changelog.rst

@@ -92,6 +92,8 @@ Detailed list of changes
 
 - Splits layout: Fix the ``move_to_screen_edge`` action breaking when only a single window is present (:iss:`7621`)
 
+- Add support for in-band window resize notifications (:iss:`7642`)
+
 0.35.2 [2024-06-22]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

kitty/fast_data_types.pyi

@@ -1131,6 +1131,7 @@ class Screen:
     historybuf: HistoryBuf
     linebuf: LineBuf
     in_bracketed_paste_mode: bool
+    in_band_resize_notification: bool
     cursor_visible: bool
     scrolled_by: int
     cursor: Cursor

kitty/modes.h

@@ -85,5 +85,8 @@
 // Pending updates mode
 #define PENDING_UPDATE (2026 << 5)
 
+// In-band resize notification mode
+#define INBAND_RESIZE_NOTIFICATION (2048 << 5)
+
 // Handle Ctrl-C/Ctrl-Z mode
 #define HANDLE_TERMIOS_SIGNALS (19997 << 5)

kitty/screen.c

@@ -1153,6 +1153,12 @@ set_mode_from_const(Screen *self, unsigned int mode, bool val) {
                 log_error("Pending mode change to already current mode (%d) requested. Either pending mode expired or there is an application bug.", val);
             }
             break;
+        case INBAND_RESIZE_NOTIFICATION:
+            if (val != self->modes.mINBAND_RESIZE_NOTIFICATION) {
+                self->modes.mINBAND_RESIZE_NOTIFICATION = val;
+                if (val) CALLBACK("notify_child_of_resize", NULL);
+            }
+            break;
         default:
             private = mode >= 1 << 5;
             if (private) mode >>= 5;
@@ -1662,6 +1668,7 @@ copy_specific_mode(Screen *self, unsigned int mode, const ScreenModes *src, Scre
         SIMPLE_MODE(DECARM)
         SIMPLE_MODE(BRACKETED_PASTE)
         SIMPLE_MODE(FOCUS_TRACKING)
+        SIMPLE_MODE(INBAND_RESIZE_NOTIFICATION)
         SIMPLE_MODE(DECCKM)
         SIMPLE_MODE(DECTCEM)
         SIMPLE_MODE(DECAWM)
@@ -1702,6 +1709,7 @@ copy_specific_modes(Screen *self, const ScreenModes *src, ScreenModes *dest) {
     copy_specific_mode(self, DECARM, src, dest);
     copy_specific_mode(self, BRACKETED_PASTE, src, dest);
     copy_specific_mode(self, FOCUS_TRACKING, src, dest);
+    copy_specific_mode(self, INBAND_RESIZE_NOTIFICATION, src, dest);
     copy_specific_mode(self, DECCKM, src, dest);
     copy_specific_mode(self, DECTCEM, src, dest);
     copy_specific_mode(self, DECAWM, src, dest);
@@ -2196,6 +2204,7 @@ report_mode_status(Screen *self, unsigned int which, bool private) {
         KNOWN_MODE(DECCKM);
         KNOWN_MODE(BRACKETED_PASTE);
         KNOWN_MODE(FOCUS_TRACKING);
+        KNOWN_MODE(INBAND_RESIZE_NOTIFICATION);
 #undef KNOWN_MODE
         case ALTERNATE_SCREEN:
             ans = self->linebuf == self->alt_linebuf ? 1 : 2; break;
@@ -3830,6 +3839,7 @@ WRAP0(clear_scrollback)
 
 MODE_GETSET(in_bracketed_paste_mode, BRACKETED_PASTE)
 MODE_GETSET(focus_tracking_enabled, FOCUS_TRACKING)
+MODE_GETSET(in_band_resize_notification, INBAND_RESIZE_NOTIFICATION)
 MODE_GETSET(auto_repeat_enabled, DECARM)
 MODE_GETSET(cursor_visible, DECTCEM)
 MODE_GETSET(cursor_key_mode, DECCKM)
@@ -4852,6 +4862,7 @@ static PyGetSetDef getsetters[] = {
     GETSET(in_bracketed_paste_mode)
     GETSET(auto_repeat_enabled)
     GETSET(focus_tracking_enabled)
+    GETSET(in_band_resize_notification)
     GETSET(cursor_visible)
     GETSET(cursor_key_mode)
     GETSET(disable_ligatures)

kitty/screen.h

@@ -14,7 +14,7 @@ typedef enum ScrollTypes { SCROLL_LINE = -999999, SCROLL_PAGE, SCROLL_FULL } Scr
 
 typedef struct {
     bool mLNM, mIRM, mDECTCEM, mDECSCNM, mDECOM, mDECAWM, mDECCOLM, mDECARM, mDECCKM,
-         mBRACKETED_PASTE, mFOCUS_TRACKING, mDECSACE, mHANDLE_TERMIOS_SIGNALS;
+         mBRACKETED_PASTE, mFOCUS_TRACKING, mDECSACE, mHANDLE_TERMIOS_SIGNALS, mINBAND_RESIZE_NOTIFICATION;
     MouseTrackingMode mouse_tracking_mode;
     MouseTrackingProtocol mouse_tracking_protocol;
 } ScreenModes;

kitty/window.py

@@ -45,6 +45,7 @@ from .fast_data_types import (
     CURSOR_BEAM,
     CURSOR_BLOCK,
     CURSOR_UNDERLINE,
+    ESC_CSI,
     ESC_DCS,
     ESC_OSC,
     GLFW_MOD_CONTROL,
@@ -862,6 +863,8 @@ class Window:
             boss = get_boss()
             boss.child_monitor.resize_pty(self.id, *current_pty_size)
             self.last_resized_at = monotonic()
+            self.last_reported_pty_size = current_pty_size
+            self.notify_child_of_resize()
             if not self.child_is_launched:
                 self.child.mark_terminal_ready()
                 self.child_is_launched = True
@@ -871,7 +874,6 @@ class Window:
                     print(f'[{now:.3f}] Child launched', file=sys.stderr)
             elif boss.args.debug_rendering:
                 print(f'[{monotonic():.3f}] SIGWINCH sent to child in window: {self.id} with size: {current_pty_size}', file=sys.stderr)
-            self.last_reported_pty_size = current_pty_size
         else:
             mark_os_window_dirty(self.os_window_id)
 
@@ -1222,6 +1224,10 @@ class Window:
         identifier = sanitize_identifier_pat().sub('', identifier)
         self.screen.send_escape_code_to_child(ESC_OSC, f'99;i={identifier};')
 
+    def notify_child_of_resize(self) -> None:
+        pty_size = self.last_reported_pty_size
+        if pty_size[0] > -1 and self.screen.in_band_resize_notification:
+            self.screen.send_escape_code_to_child(ESC_CSI, f'48;{pty_size[0]};{pty_size[1]};{pty_size[3]};{pty_size[2]}t')
 
     def set_dynamic_color(self, code: int, value: Union[str, bytes, memoryview] = '') -> None:
         if isinstance(value, (bytes, memoryview)):

kitty_tests/__init__.py

@@ -50,6 +50,9 @@ class Callbacks:
     def write(self, data) -> None:
         self.wtcbuf += bytes(data)
 
+    def notify_child_of_resize(self):
+        self.num_of_resize_events += 1
+
     def title_changed(self, data, is_base64=False) -> None:
         self.titlebuf.append(process_title_from_child(data, is_base64, ''))
 
@@ -106,6 +109,7 @@ class Callbacks:
         self.last_cmd_exit_status = sys.maxsize
         self.last_cmd_cmdline = ''
         self.last_cmd_at = 0
+        self.num_of_resize_events = 0
 
     def on_bell(self) -> None:
         self.bell_count += 1

kitty_tests/screen.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
-from kitty.fast_data_types import DECAWM, DECCOLM, DECOM, IRM, VT_PARSER_BUFFER_SIZE, Cursor
+from kitty.fast_data_types import DECAWM, DECCOLM, DECOM, IRM, VT_PARSER_BUFFER_SIZE, Cursor, ESC_CSI
 from kitty.marks import marker_from_function, marker_from_regex
 from kitty.window import pagerhist
 
@@ -304,6 +304,14 @@ class TestScreen(BaseTest):
         s.draw('x' * len(str(s.line(1))))
         s.resize(s.lines, s.columns + 4)
         self.ae(str(s.linebuf), 'xxx\nxx\nbb\n\n')
+        s = self.create_screen()
+        c = s.callbacks
+        parse_bytes(s, b'\x1b[?2048$p')  # ]
+        self.ae(c.wtcbuf, b'\x1b[?2048;2$y')  # ]
+        c.clear()
+        parse_bytes(s, b'\x1b[?2048h\x1b[?2048$p')  # ]
+        self.ae(c.wtcbuf, b'\x1b[?2048;1$y')  # ]
+        self.ae(c.num_of_resize_events, 1)
 
     def test_cursor_after_resize(self):