writer thread

CHANGELOG.md

@@ -15,12 +15,14 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - `DOMNode.query_one` now raises a `TooManyMatches` exception if there is
   more than one matching node.
   https://github.com/Textualize/textual/issues/1096
+- `App.mount` and `Widget.mount` have new `before` and `after` parameters https://github.com/Textualize/textual/issues/778
 
 ### Added
 
 - Added `init` param to reactive.watch
 - `CSS_PATH` can now be a list of CSS files https://github.com/Textualize/textual/pull/1079
 - Added `DOMQuery.only_one` https://github.com/Textualize/textual/issues/1096
+- Writes to stdout are now done in a thread, for smoother animation. https://github.com/Textualize/textual/pull/1104
 
 ## [0.3.0] - 2022-10-31
 

src/textual/app.py

@@ -6,24 +6,25 @@
 import os
 import platform
 import sys
+import threading
 import unicodedata
 import warnings
 from asyncio import Task
-from contextlib import asynccontextmanager
-from contextlib import redirect_stderr, redirect_stdout
+from contextlib import asynccontextmanager, redirect_stderr, redirect_stdout
 from datetime import datetime
 from pathlib import Path, PurePath
+from queue import Queue
 from time import perf_counter
 from typing import (
+    TYPE_CHECKING,
     Any,
     Generic,
     Iterable,
+    List,
     Type,
-    TYPE_CHECKING,
     TypeVar,
-    cast,
     Union,
-    List,
+    cast,
 )
 from weakref import WeakSet, WeakValueDictionary
 
@@ -36,14 +37,14 @@
 from rich.traceback import Traceback
 
 from . import Logger, LogGroup, LogVerbosity, actions, events, log, messages
-from ._animator import Animator, DEFAULT_EASING, Animatable, EasingFunction
+from ._animator import DEFAULT_EASING, Animatable, Animator, EasingFunction
 from ._ansi_sequences import SYNC_END, SYNC_START
 from ._callback import invoke
 from ._context import active_app
 from ._event_broker import NoHandler, extract_handler_actions
 from ._filter import LineFilter, Monochrome
 from ._path import _make_path_object_relative
-from ._typing import TypeAlias
+from ._typing import TypeAlias, Final
 from .binding import Binding, Bindings
 from .css.query import NoMatches
 from .css.stylesheet import Stylesheet
@@ -128,13 +129,77 @@ class CssPathError(Exception):
 
 
 class _NullFile:
+    """A file-like where writes go nowhere."""
+
     def write(self, text: str) -> None:
         pass
 
     def flush(self) -> None:
         pass
 
 
+MAX_QUEUED_WRITES: Final[int] = 30
+
+
+class _WriterThread(threading.Thread):
+    """A thread / file-like to do writes to stdout in the background."""
+
+    def __init__(self) -> None:
+        super().__init__(daemon=True)
+        self._queue: Queue[str | None] = Queue(MAX_QUEUED_WRITES)
+        self._file = sys.__stdout__
+
+    def write(self, text: str) -> None:
+        """Write text. Text will be enqueued for writing.
+
+        Args:
+            text (str): Text to write to the file.
+        """
+        self._queue.put(text)
+
+    def isatty(self) -> bool:
+        """Pretend to be a terminal.
+
+        Returns:
+            bool: True if this is a tty.
+        """
+        return True
+
+    def fileno(self) -> int:
+        """Get file handle number.
+
+        Returns:
+            int: File number of proxied file.
+        """
+        return self._file.fileno()
+
+    def flush(self) -> None:
+        """Flush the file (a no-op, because flush is done in the thread)."""
+        return
+
+    def run(self) -> None:
+        """Run the thread."""
+        write = self._file.write
+        flush = self._file.flush
+        get = self._queue.get
+        qsize = self._queue.qsize
+        # Read from the queue, write to the file.
+        # Flush when there is a break.
+        while True:
+            text: str | None = get()
+            empty = qsize() == 0
+            if text is None:
+                break
+            write(text)
+            if empty:
+                flush()
+
+    def stop(self) -> None:
+        """Stop the thread, and block until it finished."""
+        self._queue.put(None)
+        self.join()
+
+
 CSSPathType = Union[str, PurePath, List[Union[str, PurePath]], None]
 
 
@@ -192,8 +257,17 @@ def __init__(
         no_color = environ.pop("NO_COLOR", None)
         if no_color is not None:
             self._filter = Monochrome()
+
+        self._writer_thread: _WriterThread | None = None
+        if sys.__stdout__ is None:
+            file = _NullFile()
+        else:
+            self._writer_thread = _WriterThread()
+            self._writer_thread.start()
+            file = self._writer_thread
+
         self.console = Console(
-            file=sys.__stdout__ if sys.__stdout__ is not None else _NullFile(),
+            file=file,
             markup=False,
             highlight=False,
             emoji=False,
@@ -1502,6 +1576,9 @@ async def _shutdown(self) -> None:
         if self.devtools is not None and self.devtools.is_connected:
             await self._disconnect_devtools()
 
+        if self._writer_thread is not None:
+            self._writer_thread.stop()
+
     async def _on_exit_app(self) -> None:
         await self._message_queue.put(None)
 

src/textual/demo.css

@@ -1,5 +1,5 @@
  *  {
-    transition: background 250ms linear, color 250ms linear;
+    transition: background 500ms in_out_cubic, color 500ms in_out_cubic;
 }
 
 Screen {

src/textual/demo.py

@@ -219,7 +219,7 @@ def compose(self) -> ComposeResult:
 
     def on_button_pressed(self, event: Button.Pressed) -> None:
         self.app.add_note("[b magenta]Start!")
-        self.app.query_one(".location-first").scroll_visible(speed=50, top=True)
+        self.app.query_one(".location-first").scroll_visible(duration=0.5, top=True)
 
 
 class OptionGroup(Container):
@@ -272,7 +272,7 @@ def __init__(self, label: str, reveal: str) -> None:
         self.reveal = reveal
 
     def on_click(self) -> None:
-        self.app.query_one(self.reveal).scroll_visible(top=True)
+        self.app.query_one(self.reveal).scroll_visible(top=True, duration=0.5)
         self.app.add_note(f"Scrolling to [b]{self.reveal}[/b]")
 
 

src/textual/screen.py

@@ -18,8 +18,8 @@
 from .widget import Widget
 
 
-# Screen updates will be batched so that they don't happen more often than 60 times per second:
-UPDATE_PERIOD: Final = 1 / 60
+# Screen updates will be batched so that they don't happen more often than 120 times per second:
+UPDATE_PERIOD: Final[float] = 1 / 120
 
 
 @rich.repr.auto