Merge pull request #6105 from Textualize/layout-optimize

optimize layout

Author: willmcgugan

CHANGELOG.md

@@ -11,10 +11,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Eager tasks are now enabled On Python3.12 and above https://github.com/Textualize/textual/pull/6102
 
-
 ### Added
 
 - Added `DOMNode.displayed_and_visible_children` https://github.com/Textualize/textual/pull/6102
+- Added `Widget.process_layout` https://github.com/Textualize/textual/pull/6105
+- Added `App.viewport_size` https://github.com/Textualize/textual/pull/6105
+- Added `Screen.size` https://github.com/Textualize/textual/pull/6105
 
 ## [6.1.0] - 2025-08-01
 

src/textual/_arrange.py

@@ -31,6 +31,11 @@ def _build_layers(widgets: Iterable[Widget]) -> Mapping[str, Sequence[Widget]]:
  return layers
 
 
+_get_dock = attrgetter("styles.is_docked")
+_get_split = attrgetter("styles.is_split")
+_get_display = attrgetter("display")
+
+
 def arrange(
  widget: Widget,
  children: Sequence[Widget],
@@ -50,22 +55,17 @@ def arrange(
  """
 
  placements: list[WidgetPlacement] = []
- scroll_spacing = Spacing()
-
- get_dock = attrgetter("styles.is_docked")
- get_split = attrgetter("styles.is_split")
- get_display = attrgetter("styles.display")
-
+ scroll_spacing = NULL_SPACING
  styles = widget.styles
 
  # Widgets which will be displayed
- display_widgets = [child for child in children if get_display(child) != "none"]
+ display_widgets = list(filter(_get_display, children))
  # Widgets organized into layers
  layers = _build_layers(display_widgets)
 
  for widgets in layers.values():
  # Partition widgets into split widgets and non-split widgets
- non_split_widgets, split_widgets = partition(get_split, widgets)
+ non_split_widgets, split_widgets = partition(_get_split, widgets)
  if split_widgets:
  _split_placements, dock_region = _arrange_split_widgets(
  split_widgets, size, viewport
@@ -78,7 +78,7 @@ def arrange(
 
  # Partition widgets into "layout" widgets (those that appears in the normal 'flow' of the
  # document), and "dock" widgets which are positioned relative to an edge
- layout_widgets, dock_widgets = partition(get_dock, non_split_widgets)
+ layout_widgets, dock_widgets = partition(_get_dock, non_split_widgets)
 
  # Arrange docked widgets
  if dock_widgets:
@@ -94,8 +94,10 @@ def arrange(
 
  if layout_widgets:
  # Arrange layout widgets (i.e. not docked)
- layout_placements = widget.layout.arrange(
- widget, layout_widgets, dock_region.size, greedy=not optimal
+ layout_placements = widget.process_layout(
+ widget.layout.arrange(
+ widget, layout_widgets, dock_region.size, greedy=not optimal
+ )
  )
  scroll_spacing = scroll_spacing.grow_maximum(dock_spacing)
  placement_offset = dock_region.offset

src/textual/_profile.py

@@ -10,10 +10,17 @@
 
 
 @contextlib.contextmanager
-def timer(subject: str = "time") -> Generator[None, None, None]:
- """print the elapsed time. (only used in debugging)"""
+def timer(subject: str = "time", threshold: float = 0) -> Generator[None, None, None]:
+ """print the elapsed time. (only used in debugging).
+
+ Args:
+ subject: Text shown in log.
+ threshold: Time in second after which the log is written.
+
+ """
  start = perf_counter()
  yield
  elapsed = perf_counter() - start
- elapsed_ms = elapsed * 1000
- log(f"{subject} elapsed {elapsed_ms:.4f}ms")
+ if elapsed >= threshold:
+ elapsed_ms = elapsed * 1000
+ log(f"{subject} elapsed {elapsed_ms:.4f}ms")

src/textual/app.py

@@ -1565,6 +1565,14 @@ def size(self) -> Size:
  width, height = self.console.size
  return Size(width, height)
 
+ @property
+ def viewport_size(self) -> Size:
+ """Get the viewport size (size of the screen)."""
+ try:
+ return self.screen.size
+ except (ScreenStackError, NoScreen):
+ return self.size
+
  def _get_inline_height(self) -> int:
  """Get the inline height (height when in inline mode).
 

src/textual/layouts/grid.py

@@ -60,7 +60,7 @@ def arrange(
  table_size_columns -= 1
 
  table_size_rows = styles.grid_size_rows
- viewport = parent.screen.size
+ viewport = parent.app.viewport_size
  keyline_style, _keyline_color = styles.keyline
  offset = (0, 0)
  gutter_spacing: Spacing | None

src/textual/layouts/horizontal.py

@@ -25,7 +25,7 @@ def arrange(
  parent.pre_layout(self)
  placements: list[WidgetPlacement] = []
  add_placement = placements.append
- viewport = parent.app.size
+ viewport = parent.app.viewport_size
 
  child_styles = [child.styles for child in children]
  box_margins: list[Spacing] = [

src/textual/layouts/stream.py

@@ -37,7 +37,7 @@ def arrange(
  parent.pre_layout(self)
  if not children:
  return []
- viewport = parent.app.size
+ viewport = parent.app.viewport_size
 
  _Region = Region
  _WidgetPlacement = WidgetPlacement
@@ -81,3 +81,37 @@ def arrange(
  y += height
 
  return placements
+
+ def get_content_width(self, widget: Widget, container: Size, viewport: Size) -> int:
+ """Get the optimal content width by arranging children.
+
+ Args:
+ widget: The container widget.
+ container: The container size.
+ viewport: The viewport size.
+
+ Returns:
+ Width of the content.
+ """
+ return widget.scrollable_content_region.width
+
+ def get_content_height(
+ self, widget: Widget, container: Size, viewport: Size, width: int
+ ) -> int:
+ """Get the content height.
+
+ Args:
+ widget: The container widget.
+ container: The container size.
+ viewport: The viewport.
+ width: The content width.
+
+ Returns:
+ Content height (in lines).
+ """
+ if widget._nodes:
+ arrangement = widget._arrange(Size(width, 0))
+ height = arrangement.total_region.height
+ else:
+ height = 0
+ return height

src/textual/layouts/vertical.py

@@ -23,7 +23,7 @@ def arrange(
  parent.pre_layout(self)
  placements: list[WidgetPlacement] = []
  add_placement = placements.append
- viewport = parent.app.size
+ viewport = parent.app.viewport_size
 
  child_styles = [child.styles for child in children]
  box_margins: list[Spacing] = [

src/textual/screen.py

@@ -341,6 +341,11 @@ def layers(self) -> tuple[str, ...]:
  extras.append("_tooltips")
  return (*super().layers, *extras)
 
+ @property
+ def size(self) -> Size:
+ """The size of the screen."""
+ return self.app.size - self.styles.gutter.totals
+
  def _watch_focused(self):
  self.refresh_bindings()
 
@@ -512,7 +517,7 @@ def get_maximize_widgets(maximized: Widget) -> list[Widget]:
  else self._nodes
  ),
  size,
- self.screen.size,
+ self.size,
  False,
  )
 

src/textual/widget.py

@@ -79,7 +79,7 @@
  Spacing,
  clamp,
 )
-from textual.layout import Layout
+from textual.layout import Layout, WidgetPlacement
 from textual.layouts.vertical import VerticalLayout
 from textual.message import Message
 from textual.messages import CallbackType, Prune
@@ -460,7 +460,7 @@ def __init__(
  self._content_height_cache: tuple[object, int] = (None, 0)
 
  self._arrangement_cache: FIFOCache[
- tuple[Size, int, Widget], DockArrangeResult
+ tuple[Size, int, Widget | None], DockArrangeResult
  ] = FIFOCache(4)
 
  self._styles_cache = StylesCache()
@@ -605,7 +605,7 @@ def offset(self) -> Offset:
  Returns:
  Relative offset.
  """
- return self.styles.offset.resolve(self.size, self.app.size)
+ return self.styles.offset.resolve(self.size, self.screen.size)
 
  @offset.setter
  def offset(self, offset: tuple[int, int]) -> None:
@@ -717,10 +717,26 @@ def _cover(self, widget: Widget) -> None:
  self._uncover()
  self._cover_widget = widget
  widget._parent = self
+ widget._start_messages()
  widget._post_register(self.app)
  self.app.stylesheet.apply(widget)
  self.refresh(layout=True)
- widget._start_messages()
+
+ def process_layout(
+ self, placements: list[WidgetPlacement]
+ ) -> list[WidgetPlacement]:
+ """A hook to allow for the manipulation of widget placements before rendering.
+
+ You could use this as a way to modify the positions / margins of widgets if your requirement is
+ not supported in TCSS. In practice, this method is rarely needed!
+
+ Args:
+ placements: A list of [`WidgetPlacement`][textual.layout.WidgetPlacement] objects.
+
+ Returns:
+ A new list of placements.
+ """
+ return placements
 
  def _uncover(self) -> None:
  """Remove any widget, previously set via [`_cover`][textual.widget.Widget._cover]."""