Fr unit

sandbox/will/fr.py

@@ -0,0 +1,96 @@
+from textual.app import App, ComposeResult
+from textual.containers import Horizontal, Vertical
+from textual.widgets import Static
+
+
+class StaticText(Static):
+    pass
+
+
+class Header(Static):
+    pass
+
+
+class Footer(Static):
+    pass
+
+
+class FrApp(App):
+
+    CSS = """
+    Screen {
+        layout: horizontal;
+        align: center middle;
+
+    }
+
+    Vertical {
+
+    }
+
+    Header {
+        background: $boost;
+
+        content-align: center middle;
+        text-align: center;
+        color: $text;
+        height: 3;
+        border: tall $warning;
+    }
+
+    Horizontal {
+        height: 1fr;
+        align: center middle;
+    }
+
+    Footer {
+        background: $boost;
+
+        content-align: center middle;
+        text-align: center;
+
+        color: $text;
+        height: 6;
+        border: tall $warning;
+    }
+
+    StaticText {
+        background: $boost;
+        height: 8;
+        content-align: center middle;
+        text-align: center;
+        color: $text;
+    }
+
+    #foo {
+        width: 10; 
+        border: tall $primary;
+    }
+
+    #bar {
+        width: 1fr;
+        border: tall $error;
+
+    }
+
+    #baz {
+        width: 20;
+        border: tall $success;
+    }
+
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Vertical(
+            Header("HEADER"),
+            Horizontal(
+                StaticText("foo", id="foo"),
+                StaticText("bar", id="bar"),
+                StaticText("baz", id="baz"),
+            ),
+            Footer("FOOTER"),
+        )
+
+
+app = FrApp()
+app.run()

src/textual/_arrange.py

@@ -60,10 +60,9 @@ def arrange(
         for dock_widget in dock_widgets:
             edge = dock_widget.styles.dock
 
-            fraction_unit = Fraction(
-                size.height if edge in ("top", "bottom") else size.width
+            box_model = dock_widget._get_box_model(
+                size, viewport, Fraction(size.width), Fraction(size.height)
             )
-            box_model = dock_widget._get_box_model(size, viewport, fraction_unit)
             widget_width_fraction, widget_height_fraction, margin = box_model
 
             widget_width = int(widget_width_fraction) + margin.width

src/textual/_resolve.py

@@ -1,12 +1,23 @@
 from __future__ import annotations
 
+import sys
 from fractions import Fraction
 from itertools import accumulate
-from typing import cast, Sequence
+from typing import cast, Sequence, TYPE_CHECKING
 
+from .box_model import BoxModel
 from .css.scalar import Scalar
 from .geometry import Size
 
+if TYPE_CHECKING:
+    from .widget import Widget
+
+
+if sys.version_info >= (3, 8):
+    from typing import Literal
+else:
+    from typing_extensions import Literal
+
 
 def resolve(
     dimensions: Sequence[Scalar],
@@ -71,3 +82,79 @@ def resolve(
     ]
 
     return results
+
+
+def resolve_box_models(
+    dimensions: list[Scalar | None],
+    widgets: list[Widget],
+    size: Size,
+    parent_size: Size,
+    dimension: Literal["width", "height"] = "width",
+) -> list[BoxModel]:
+    """Resolve box models for a list of dimensions
+
+    Args:
+        dimensions (list[Scalar  |  None]): A list of Scalars or Nones for each dimension.
+        widgets (list[Widget]): Widgets in resolve.
+        size (Size): size of container.
+        parent_size (Size): Size of parent.
+        dimensions (Literal["width", "height"]): Which dimension to resolve.
+
+    Returns:
+        list[BoxModel]: List of resolved box models.
+    """
+
+    fraction_width = Fraction(size.width)
+    fraction_height = Fraction(size.height)
+    box_models: list[BoxModel | None] = [
+        (
+            None
+            if dimension is not None and dimension.is_fraction
+            else widget._get_box_model(
+                size, parent_size, fraction_width, fraction_height
+            )
+        )
+        for (dimension, widget) in zip(dimensions, widgets)
+    ]
+
+    if dimension == "width":
+        total_remaining = sum(
+            box_model.width for box_model in box_models if box_model is not None
+        )
+        remaining_space = max(0, size.width - total_remaining)
+    else:
+        total_remaining = sum(
+            box_model.height for box_model in box_models if box_model is not None
+        )
+        remaining_space = max(0, size.height - total_remaining)
+
+    fraction_unit = Fraction(
+        remaining_space,
+        int(
+            sum(
+                dimension.value
+                for dimension in dimensions
+                if dimension and dimension.is_fraction
+            )
+        )
+        or 1,
+    )
+    if dimension == "width":
+        width_fraction = fraction_unit
+        height_fraction = Fraction(size.height)
+    else:
+        width_fraction = Fraction(size.width)
+        height_fraction = fraction_unit
+
+    box_models = [
+        box_model
+        or widget._get_box_model(
+            size,
+            parent_size,
+            width_fraction,
+            height_fraction,
+        )
+        for widget, box_model in zip(widgets, box_models)
+    ]
+
+    return cast("list[BoxModel]", box_models)

src/textual/app.py

@@ -1139,7 +1139,12 @@ async def on_screenshot():
         self.set_timer(screenshot_timer, on_screenshot, name="screenshot timer")
 
     async def _on_compose(self) -> None:
-        widgets = list(self.compose())
+        try:
+            widgets = list(self.compose())
+        except TypeError as error:
+            raise TypeError(
+                f"{self!r} compose() returned an invalid response; {error}"
+            ) from None
         await self.mount_all(widgets)
 
     def _on_idle(self) -> None:

src/textual/box_model.py

@@ -20,7 +20,8 @@ def get_box_model(
     styles: StylesBase,
     container: Size,
     viewport: Size,
-    fraction_unit: Fraction,
+    width_fraction: Fraction,
+    height_fraction: Fraction,
     get_content_width: Callable[[Size, Size], int],
     get_content_height: Callable[[Size, Size, int], int],
 ) -> BoxModel:
@@ -30,6 +31,8 @@ def get_box_model(
         styles (StylesBase): Styles object.
         container (Size): The size of the widget container.
         viewport (Size): The viewport size.
+        width_fraction (Fraction): A fraction used for 1 `fr` unit on the width dimension.
+        height_fraction (Fraction):A fraction used for 1 `fr` unit on the height dimension.
         get_auto_width (Callable): A callable which accepts container size and parent size and returns a width.
         get_auto_height (Callable): A callable which accepts container size and parent size and returns a height.
 
@@ -63,22 +66,22 @@ def get_box_model(
         # An explicit width
         styles_width = styles.width
         content_width = styles_width.resolve_dimension(
-            sizing_container - styles.margin.totals, viewport, fraction_unit
+            sizing_container - styles.margin.totals, viewport, width_fraction
         )
         if is_border_box and styles_width.excludes_border:
             content_width -= gutter.width
 
     if styles.min_width is not None:
         # Restrict to minimum width, if set
         min_width = styles.min_width.resolve_dimension(
-            content_container, viewport, fraction_unit
+            content_container, viewport, width_fraction
         )
         content_width = max(content_width, min_width)
 
     if styles.max_width is not None:
         # Restrict to maximum width, if set
         max_width = styles.max_width.resolve_dimension(
-            content_container, viewport, fraction_unit
+            content_container, viewport, width_fraction
         )
         if is_border_box:
             max_width -= gutter.width
@@ -98,22 +101,22 @@ def get_box_model(
         styles_height = styles.height
         # Explicit height set
         content_height = styles_height.resolve_dimension(
-            sizing_container - styles.margin.totals, viewport, fraction_unit
+            sizing_container - styles.margin.totals, viewport, height_fraction
         )
         if is_border_box and styles_height.excludes_border:
             content_height -= gutter.height
 
     if styles.min_height is not None:
         # Restrict to minimum height, if set
         min_height = styles.min_height.resolve_dimension(
-            content_container, viewport, fraction_unit
+            content_container, viewport, height_fraction
         )
         content_height = max(content_height, min_height)
 
     if styles.max_height is not None:
         # Restrict maximum height, if set
         max_height = styles.max_height.resolve_dimension(
-            content_container, viewport, fraction_unit
+            content_container, viewport, height_fraction
         )
         content_height = min(content_height, max_height)
 

src/textual/layouts/grid.py

@@ -145,9 +145,7 @@ def repeat_scalars(scalars: Iterable[Scalar], count: int) -> list[Scalar]:
             y2, cell_height = rows[min(max_row, row + row_span)]
             cell_size = Size(cell_width + x2 - x, cell_height + y2 - y)
             width, height, margin = widget._get_box_model(
-                cell_size,
-                viewport,
-                fraction_unit,
+                cell_size, viewport, fraction_unit, fraction_unit
             )
             region = (
                 Region(x, y, int(width + margin.width), int(height + margin.height))

src/textual/layouts/horizontal.py

@@ -1,12 +1,11 @@
 from __future__ import annotations
 
 from fractions import Fraction
-from typing import cast
 
-from textual.geometry import Size, Region
-from textual._layout import ArrangeResult, Layout, WidgetPlacement
-
-from textual.widget import Widget
+from .._resolve import resolve_box_models
+from ..geometry import Size, Region
+from .._layout import ArrangeResult, Layout, WidgetPlacement
+from ..widget import Widget
 
 
 class HorizontalLayout(Layout):
@@ -22,20 +21,16 @@ def arrange(
 
         placements: list[WidgetPlacement] = []
         add_placement = placements.append
-
         x = max_height = Fraction(0)
         parent_size = parent.outer_size
 
-        styles = [child.styles for child in children if child.styles.width is not None]
-        total_fraction = sum(
-            [int(style.width.value) for style in styles if style.width.is_fraction]
+        box_models = resolve_box_models(
+            [child.styles.width for child in children],
+            children,
+            size,
+            parent_size,
+            dimension="width",
         )
-        fraction_unit = Fraction(size.width, total_fraction or 1)
-
-        box_models = [
-            widget._get_box_model(size, parent_size, fraction_unit)
-            for widget in cast("list[Widget]", children)
-        ]
 
         margins = [
             max((box1.margin.right, box2.margin.left))

src/textual/layouts/vertical.py

@@ -3,6 +3,7 @@
 from fractions import Fraction
 from typing import TYPE_CHECKING
 
+from .._resolve import resolve_box_models
 from ..geometry import Region, Size
 from .._layout import ArrangeResult, Layout, WidgetPlacement
 
@@ -21,19 +22,15 @@ def arrange(
 
         placements: list[WidgetPlacement] = []
         add_placement = placements.append
-
         parent_size = parent.outer_size
 
-        styles = [child.styles for child in children if child.styles.height is not None]
-        total_fraction = sum(
-            [int(style.height.value) for style in styles if style.height.is_fraction]
+        box_models = resolve_box_models(
+            [child.styles.height for child in children],
+            children,
+            size,
+            parent_size,
+            dimension="height",
         )
-        fraction_unit = Fraction(size.height, total_fraction or 1)
-
-        box_models = [
-            widget._get_box_model(size, parent_size, fraction_unit)
-            for widget in children
-        ]
 
         margins = [
             max((box1.margin.bottom, box2.margin.top))