[terminal buffering] Add support for the "mode 2026"

That task is definitely way more complicated that it seemed to be 😅

sandbox/vertical_container.py

@@ -39,7 +39,7 @@ class Introduction(Widget):
     }
     """
 
-    def render(self) -> RenderableType:
+    def render(self, styles) -> RenderableType:
         return Text(
             "Press '-' and '+' to add or remove placeholders.", justify="center"
         )

src/textual/_ansi_sequences.py

@@ -1,9 +1,14 @@
 from typing import Dict, Tuple
 
+from ._terminal_modes import (
+    get__mode_report_sequence,
+    Mode,
+    ModeReportParameter,
+)
 from .keys import Keys
 
 # Mapping of vt100 escape codes to Keys.
-ANSI_SEQUENCES: Dict[str, Tuple[Keys, ...]] = {
+ANSI_SEQUENCES_KEYS: Dict[str, Tuple[Keys, ...]] = {
     # Control keys.
     "\r": (Keys.Enter,),
     "\x00": (Keys.ControlAt,),  # Control-At (Also for Ctrl-Space)
@@ -299,3 +304,12 @@ ANSI_SEQUENCES: Dict[str, Tuple[Keys, ...]] = {
     "\x1b[1;8x": (Keys.Escape, Keys.ControlShift8),
     "\x1b[1;8y": (Keys.Escape, Keys.ControlShift9),
 }
+
+
+# Mapping of escape codes to report whether they support a "mode" we requested.
+ANSI_SEQUENCES_MODE_REPORTS: Dict[str, Tuple[Mode, ModeReportParameter]] = {
+    get__mode_report_sequence(mode, parameter): (mode, parameter)
+    for mode, parameter in [
+        (mode, parameter) for parameter in ModeReportParameter for mode in Mode
+    ]
+}

src/textual/_terminal_features.py

@@ -0,0 +1,84 @@
+from __future__ import annotations
+import os
+import platform
+from dataclasses import dataclass
+
+
+@dataclass
+class TerminalSupportedFeatures:
+    """
+    Handles information about the features the current terminal emulator seems to support.
+    """
+
+    iterm2_synchronized_update: bool = False
+    """@link https://gitlab.com/gnachman/iterm2/-/wikis/synchronized-updates-spec"""
+    mode2026_synchronized_update: bool = False
+    """@link https://gist.github.com/christianparpart/d8a62cc1ab659194337d73e399004036"""
+
+    @classmethod
+    def from_autodetect(cls) -> TerminalSupportedFeatures:
+        """
+        Tries to autodetect various features we can work with the terminal emulator we're running in,
+        and returns an instance of `TerminalSupportedFeatures` on which matching property will be set to `True`
+        for features that seem to be usable.
+
+        Returns:
+            TerminalSupportedFeatures: a new TerminalSupportedFeatures
+        """
+
+        # Using macOS, but not using the default terminal: let's assume we're on iTerm2
+        iterm2_synchronized_update = (
+            platform.system() == "Darwin"
+            and os.environ.get("TERM_PROGRAM", "") != "Apple_Terminal"
+        )
+
+        # Detecting "mode2026" is more complicated, as we have to use an async request/response
+        # machinery with the terminal emulator - for now we should just assume it's not supported.
+        # See the use of the Mode and ModeReportParameter classes in the Textual code to check this machinery.
+        mode2026_synchronized_update = False
+
+        return cls(
+            iterm2_synchronized_update=iterm2_synchronized_update,
+            mode2026_synchronized_update=mode2026_synchronized_update,
+        )
+
+    @property
+    def supports_synchronized_update(self) -> bool:
+        """
+        Tells the caller if the current terminal emulator seems to support "synchronised updates"
+        (i.e. "buffered" updates).
+        At the moment we support the iTerm2 specific one, as wel las the more generic "mode 2026".
+
+        Returns:
+            bool: whether the terminal seems to support buffered mode or not
+        """
+        return self.iterm2_synchronized_update or self.mode2026_synchronized_update
+
+    def synchronized_update_sequences(self) -> tuple[str, str]:
+        """
+        Returns the ANSI sequence that we should send to the terminal to tell it that
+        it should buffer the content we're about to send, as well as the ANIS sequence to end the buffering.
+        If the terminal doesn't seem to support synchronised updates both strings will be empty.
+
+        Returns:
+            tuple[str, str]: the start and end ANSI sequences, respectively. They will both be empty strings
+                if the terminal emulator doesn't seem to support the "synchronised updates" mode.
+        """
+        return (
+            self._synchronized_update_start_sequence(),
+            self._synchronized_update_end_sequence(),
+        )
+
+    def _synchronized_update_start_sequence(self) -> str:
+        if self.iterm2_synchronized_update:
+            return "\x1bP=1s\x1b\\"
+        if self.mode2026_synchronized_update:
+            return "\x1b[?2026h"
+        return ""
+
+    def _synchronized_update_end_sequence(self) -> str:
+        if self.iterm2_synchronized_update:
+            return "\x1bP=2s\x1b\\"
+        if self.mode2026_synchronized_update:
+            return "\x1b[?2026l"
+        return ""

src/textual/_terminal_modes.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from enum import Enum, IntEnum, unique
+
+
+@unique
+class Mode(Enum):
+    # "Modes" are features that terminal emulators can optionally support
+    # We have to "request" to the emulator if they support a given feature, and they can respond with a "report"
+    # @link https://vt100.net/docs/vt510-rm/DECRQM.html
+    # @link https://vt100.net/docs/vt510-rm/DECRPM.html
+    SynchronizedOutput = "2026"
+
+
+@unique
+class ModeReportParameter(IntEnum):
+    # N.B. The values of this enum are not arbitrary: they match the ones of the spec
+    # @link https://vt100.net/docs/vt510-rm/DECRPM.html
+    NotRecognized = 0
+    Set = 1
+    Reset = 2
+    PermanentlySet = 3
+    PermanentlyReset = 4
+
+
+MODE_REPORTS_PARAMETERS_INDICATING_SUPPORT = frozenset(
+    {
+        ModeReportParameter.Set,
+        ModeReportParameter.Reset,
+        ModeReportParameter.PermanentlySet,
+        ModeReportParameter.PermanentlyReset,
+    }
+)
+
+
+def get_mode_request_sequence(mode: Mode) -> str:
+    return "\033[?" + mode.value + "$p\n"
+
+
+def get__mode_report_sequence(mode: Mode, parameter: ModeReportParameter) -> str:
+    return f"\x1b[?{mode.value};{parameter.value}$y"

src/textual/_xterm_parser.py

@@ -9,8 +9,7 @@ from . import log
 from . import events
 from ._types import MessageTarget
 from ._parser import Awaitable, Parser, TokenCallback
-from ._ansi_sequences import ANSI_SEQUENCES
+from ._ansi_sequences import ANSI_SEQUENCES_KEYS, ANSI_SEQUENCES_MODE_REPORTS
-
 
 _re_mouse_event = re.compile("^" + re.escape("\x1b[") + r"(<?[\d;]+[mM]|M...)\Z")
 
@@ -82,7 +81,8 @@ class XTermParser(Parser[events.Event]):
 
         ESC = "\x1b"
         read1 = self.read1
-        get_ansi_sequence = ANSI_SEQUENCES.get
+        get_key_ansi_sequence = ANSI_SEQUENCES_KEYS.get
+        get_mode_report_sequence = ANSI_SEQUENCES_MODE_REPORTS.get
         more_data = self.more_data
 
         while not self.is_eof:
@@ -108,12 +108,13 @@ class XTermParser(Parser[events.Event]):
                 while True:
                     sequence += yield read1()
                     self.debug_log(f"sequence={sequence!r}")
-                    keys = get_ansi_sequence(sequence, None)
+                    # Was it a pressed key event that we received?
+                    keys = get_key_ansi_sequence(sequence, None)
                     if keys is not None:
                         for key in keys:
                             on_token(events.Key(self.sender, key=key))
                         break
-                    else:
+                    # Or a mouse event?
                     mouse_match = _re_mouse_event.match(sequence)
                     if mouse_match is not None:
                         mouse_code = mouse_match.group(0)
@@ -121,8 +122,15 @@ class XTermParser(Parser[events.Event]):
                         if event:
                             on_token(event)
                         break
+                    # Or a mode report? (i.e. the terminal telling us if it supports a mode we requested)
+                    mode_report_match = get_mode_report_sequence(sequence, None)
+                    if mode_report_match is not None:
+                        mode_report, parameter = mode_report_match
+                        event = events.ModeReport(self.sender, mode_report, parameter)
+                        on_token(event)
+                        break
             else:
-                keys = get_ansi_sequence(character, None)
+                keys = get_key_ansi_sequence(character, None)
                 if keys is not None:
                     for key in keys:
                         on_token(events.Key(self.sender, key=key))

src/textual/app.py

@@ -22,6 +22,10 @@ from typing import (
     TYPE_CHECKING,
 )
 
+from ._terminal_features import TerminalSupportedFeatures
+from ._terminal_modes import Mode
+from .events import ModeReport
+
 if sys.version_info >= (3, 8):
     from typing import Literal
 else:
@@ -44,7 +48,6 @@ from ._animator import Animator
 from ._callback import invoke
 from ._context import active_app
 from ._event_broker import extract_handler_actions, NoHandler
-from ._timer import Timer
 from .binding import Bindings, NoBinding
 from .css.stylesheet import Stylesheet
 from .design import ColorSystem
@@ -143,9 +146,7 @@ class App(Generic[ReturnType], DOMNode):
         self.driver_class = driver_class or self.get_driver_class()
         self._title = title
         self._screen_stack: list[Screen] = []
-        self._sync_available = (
+        self._terminal_features = TerminalSupportedFeatures.from_autodetect()
-            os.environ.get("TERM_PROGRAM", "") != "Apple_Terminal" and not WINDOWS
-        )
 
         self.focused: Widget | None = None
         self.mouse_over: Widget | None = None
@@ -698,6 +699,7 @@ class App(Generic[ReturnType], DOMNode):
         self.log("---")
         self.log(driver=self.driver_class)
         self.log(loop=asyncio.get_running_loop())
+        self.log(terminal_features=self._terminal_features)
         self.log(features=self.features)
 
         try:
@@ -858,14 +860,18 @@ class App(Generic[ReturnType], DOMNode):
         """
         if self._running and not self._closed:
             console = self.console
-            if self._sync_available:
+            (
-                console.file.write("\x1bP=1s\x1b\\")
+                sync_update_start,
+                sync_update_end,
+            ) = self._terminal_features.synchronized_update_sequences()
+            if sync_update_start:
+                console.file.write(sync_update_start)
             try:
                 console.print(renderable)
             except Exception as error:
                 self.on_exception(error)
-            if self._sync_available:
+            if sync_update_end:
-                console.file.write("\x1bP=2s\x1b\\")
+                console.file.write(sync_update_end)
             console.file.flush()
 
     def measure(self, renderable: RenderableType, max_width=100_000) -> int:
@@ -939,6 +945,15 @@ class App(Generic[ReturnType], DOMNode):
             else:
                 # Forward the event to the view
                 await self.screen.forward_event(event)
+
+        elif isinstance(event, ModeReport):
+            if event.mode is Mode.SynchronizedOutput:
+                is_supported = event.mode_is_supported
+                log(
+                    f"SynchronizedOutput (aka 'mode2026') {'is' if is_supported else ' is not'} supported"
+                )
+                self._terminal_features.mode2026_synchronized_update = is_supported
+
         else:
             await super().on_event(event)
 

src/textual/driver.py

@@ -2,12 +2,10 @@ from __future__ import annotations
 
 import asyncio
 from time import time
-import platform
 from abc import ABC, abstractmethod
 from typing import TYPE_CHECKING
 
 from . import events
-from . import log
 from ._types import MessageTarget
 
 if TYPE_CHECKING:

src/textual/drivers/linux_driver.py

@@ -21,6 +21,7 @@ from ..driver import Driver
 from ..geometry import Size
 from .._types import MessageTarget
 from .._xterm_parser import XTermParser
+from .._terminal_modes import get_mode_request_sequence, Mode
 from .._profile import timer
 
 
@@ -123,6 +124,11 @@ class LinuxDriver(Driver):
         self._key_thread = Thread(target=self.run_input_thread, args=(loop,))
         send_size_event()
         self._key_thread.start()
+        self._request_terminal_mode_support(Mode.SynchronizedOutput)
+
+    def _request_terminal_mode_support(self, mode: Mode):
+        self.console.file.write(get_mode_request_sequence(mode) + "\n")
+        self.console.file.flush()
 
     @classmethod
     def _patch_lflag(cls, attrs: int) -> int:
@@ -214,7 +220,6 @@ class LinuxDriver(Driver):
 
 
 if __name__ == "__main__":
-    from time import sleep
     from rich.console import Console
     from .. import events
 

src/textual/events.py

@@ -6,6 +6,11 @@ import rich.repr
 from rich.style import Style
 
 from . import log
+from ._terminal_modes import (
+    Mode,
+    ModeReportParameter,
+    MODE_REPORTS_PARAMETERS_INDICATING_SUPPORT,
+)
 from .geometry import Offset, Size
 from .message import Message
 from ._types import MessageTarget
@@ -411,3 +416,37 @@ class DescendantFocus(Event, verbosity=2, bubble=True):
 
 class DescendantBlur(Event, verbosity=2, bubble=True):
     pass
+
+
+@rich.repr.auto
+class ModeReport(InputEvent):
+    """Sent when the terminals responses to a "mode "(i.e. a supported feature) request"""
+
+    __slots__ = ["mode", "report_parameter"]
+
+    def __init__(
+        self, sender: MessageTarget, mode: Mode, report_parameter: ModeReportParameter
+    ) -> None:
+        """
+
+        Args:
+            sender (MessageTarget): The sender of the event
+            mode (Mode): The mode the terminal emulator is giving us results about
+            report_parameter (ModeReportParameter): The status of this mode for the terminal emulator
+        """
+        super().__init__(sender)
+        self.mode = mode
+        self.report_parameter = report_parameter
+
+    def __rich_repr__(self) -> rich.repr.Result:
+        yield "mode", self.mode
+        yield "report_parameter", self.report_parameter
+
+    @property
+    def mode_is_supported(self) -> bool:
+        """Return True if the mode seems to be supported by the terminal emulator.
+
+        Returns:
+            bool: True if it's supported. False otherwise.
+        """
+        return self.report_parameter in MODE_REPORTS_PARAMETERS_INDICATING_SUPPORT

tests/utilities/test_app.py

@@ -13,8 +13,10 @@ from rich.console import Console
 
 from textual import events, errors
 from textual._clock import _Clock
-from textual.app import App, ComposeResult, WINDOWS
+from textual.app import WINDOWS
 from textual._context import active_app
+from textual._terminal_features import TerminalSupportedFeatures
+from textual.app import App, ComposeResult
 from textual.driver import Driver
 from textual.geometry import Size, Region
 
@@ -45,9 +47,13 @@ class AppTest(App):
         # Let's disable all features by default
         self.features = frozenset()
 
-        # We need this so the `CLEAR_SCREEN_SEQUENCE` is always sent for a screen refresh,
+        # We need this so the iTerm2 `CLEAR_SCREEN_SEQUENCE` is always sent for a screen refresh,
         # whatever the environment:
-        self._sync_available = True
+        # (we use it to slice the output into distinct full screens displays)
+        self._terminal_features = TerminalSupportedFeatures(
+            iterm2_synchronized_update=True,
+            mode2026_synchronized_update=False,
+        )
 
         self._size = size
         self._console = ConsoleTest(width=size.width, height=size.height)