Cache arrangements

src/textual/_compositor.py

@@ -26,6 +26,7 @@ from rich.style import Style
 from . import errors
 from .geometry import Region, Offset, Size
 
+from ._profile import timer
 from ._loop import loop_last
 from ._segment_tools import line_crop
 from ._types import Lines
@@ -214,6 +215,7 @@ class Compositor:
         Returns:
             ReflowResult: Hidden shown and resized widgets
         """
+        print("REFLOW")
         self._cuts = None
         self.root = parent
         self.size = size
@@ -327,9 +329,7 @@ class Compositor:
                 total_region = child_region.reset_origin
 
                 # Arrange the layout
-                placements, arranged_widgets = widget.layout.arrange(
-                    widget, child_region.size
-                )
+                placements, arranged_widgets = widget._arrange(child_region.size)
                 widgets.update(arranged_widgets)
                 placements = sorted(placements, key=get_order)
 
@@ -557,6 +557,7 @@ class Compositor:
         ]
         return segment_lines
 
+    @timer("render")
     def render(self, full: bool = False) -> RenderableType:
         """Render a layout.
 

src/textual/_layout.py

@@ -84,6 +84,6 @@ class Layout(ABC):
         if not widget.displayed_children:
             height = container.height
         else:
-            placements, widgets = self.arrange(widget, Size(width, container.height))
+            placements, widgets = widget._arrange(Size(width, container.height))
             height = max(placement.region.y_max for placement in placements)
         return height

src/textual/geometry.py

@@ -665,7 +665,17 @@ class Spacing(NamedTuple):
 
     @classmethod
     def unpack(cls, pad: SpacingDimensions) -> Spacing:
-        """Unpack padding specified in CSS style."""
+        """Unpack padding specified in CSS style.
+
+        Args:
+            pad (SpacingDimensions): An integer, or tuple of 1, 2, or 4 integers.
+
+        Raises:
+            ValueError: If `pad` is an invalid value.
+
+        Returns:
+            Spacing: New Spacing object.
+        """
         if isinstance(pad, int):
             return cls(pad, pad, pad, pad)
         pad_len = len(pad)

src/textual/widget.py

@@ -23,10 +23,12 @@ from . import errors
 from . import events
 from ._animator import BoundAnimator
 from ._border import Border
+from ._profile import timer
 from .box_model import BoxModel, get_box_model
 from ._context import active_app
 from ._types import Lines
 from .dom import DOMNode
+from ._layout import ArrangeResult
 from .geometry import clamp, Offset, Region, Size
 from .layouts.vertical import VerticalLayout
 from .message import Message
@@ -101,6 +103,9 @@ class Widget(DOMNode):
         self._content_width_cache: tuple[object, int] = (None, 0)
         self._content_height_cache: tuple[object, int] = (None, 0)
 
+        self._arrangement: ArrangeResult | None = None
+        self._arrangement_size: Size = Size()
+
         super().__init__(name=name, id=id, classes=classes)
         self.add_children(*children)
 
@@ -116,6 +121,13 @@ class Widget(DOMNode):
     show_vertical_scrollbar = Reactive(False, layout=True)
     show_horizontal_scrollbar = Reactive(False, layout=True)
 
+    def _arrange(self, size: Size) -> ArrangeResult:
+        if self._arrangement is not None and size == self._arrangement_size:
+            return self._arrangement
+        self._arrangement = self.layout.arrange(self, size)
+        self._arrangement_size = size
+        return self._arrangement
+
     def watch_show_horizontal_scrollbar(self, value: bool) -> None:
         """Watch function for show_horizontal_scrollbar attribute.
 
@@ -611,19 +623,17 @@ class Widget(DOMNode):
         """Arrange the 'chrome' widgets (typically scrollbars) for a layout element.
 
         Args:
-            size (Size): _description_
+            size (Size): Size of the containing region.
 
         Returns:
-            Iterable[tuple[Widget, Region]]: _description_
+            Iterable[tuple[Widget, Region]]: Tuples of scrollbar Widget and region.
 
-        Yields:
-            Iterator[Iterable[tuple[Widget, Region]]]: _description_
         """
         region = size.region
         show_vertical_scrollbar, show_horizontal_scrollbar = self.scrollbars_enabled
 
-        horizontal_scrollbar_thickness = self.scrollbar_size_horizontal
-        vertical_scrollbar_thickness = self.scrollbar_size_vertical
+        scrollbar_size_horizontal = self.scrollbar_size_horizontal
+        scrollbar_size_vertical = self.scrollbar_size_vertical
         if show_horizontal_scrollbar and show_vertical_scrollbar:
             (
                 _,
@@ -631,20 +641,19 @@ class Widget(DOMNode):
                 horizontal_scrollbar_region,
                 _,
             ) = region.split(
-                -vertical_scrollbar_thickness, -horizontal_scrollbar_thickness
+                -scrollbar_size_vertical,
+                -scrollbar_size_horizontal,
             )
             if vertical_scrollbar_region:
                 yield self.vertical_scrollbar, vertical_scrollbar_region
             if horizontal_scrollbar_region:
                 yield self.horizontal_scrollbar, horizontal_scrollbar_region
         elif show_vertical_scrollbar:
-            _, scrollbar_region = region.split_vertical(-vertical_scrollbar_thickness)
+            _, scrollbar_region = region.split_vertical(-scrollbar_size_vertical)
             if scrollbar_region:
                 yield self.vertical_scrollbar, scrollbar_region
         elif show_horizontal_scrollbar:
-            _, scrollbar_region = region.split_horizontal(
-                -horizontal_scrollbar_thickness
-            )
+            _, scrollbar_region = region.split_horizontal(-scrollbar_size_horizontal)
             if scrollbar_region:
                 yield self.horizontal_scrollbar, scrollbar_region
 
@@ -838,11 +847,11 @@ class Widget(DOMNode):
         """
         if self._dirty_regions:
             self._render_lines()
-            if self.is_container:
-                if self.show_horizontal_scrollbar:
-                    self.horizontal_scrollbar.refresh()
-                if self.show_vertical_scrollbar:
-                    self.vertical_scrollbar.refresh()
+            # if self.is_container:
+            #     if self.show_horizontal_scrollbar:
+            #         self.horizontal_scrollbar.refresh()
+            #     if self.show_vertical_scrollbar:
+            #         self.vertical_scrollbar.refresh()
         lines = self._render_cache.lines[start:end]
         return lines