Add horizontal layout

src/textual/layouts/factory.py

@@ -1,5 +1,6 @@
 import sys
 
+from .horizontal import HorizontalLayout
 from ..layout import Layout
 from ..layouts.dock import DockLayout
 from ..layouts.grid import GridLayout
@@ -10,8 +11,13 @@ if sys.version_info >= (3, 8):
 else:
     from typing_extensions import Literal
 
-LayoutName = Literal["dock", "grid", "vertical"]
-LAYOUT_MAP = {"dock": DockLayout, "grid": GridLayout, "vertical": VerticalLayout}
+LayoutName = Literal["dock", "grid", "vertical", "horizontal"]
+LAYOUT_MAP = {
+    "dock": DockLayout,
+    "grid": GridLayout,
+    "vertical": VerticalLayout,
+    "horizontal": HorizontalLayout,
+}
 
 
 class MissingLayout(Exception):

src/textual/layouts/horizontal.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+from typing import Iterable
+
+from textual._loop import loop_last
+from textual.css.styles import Styles
+from textual.geometry import SpacingDimensions, Spacing, Size, Offset, Region
+from textual.layout import Layout, WidgetPlacement
+from textual.view import View
+from textual.widget import Widget
+
+
+class HorizontalLayout(Layout):
+    def __init__(
+        self,
+        *,
+        z: int = 0,
+        gutter: SpacingDimensions = (0, 0, 0, 0),
+    ):
+        self.z = z
+        self.gutter = Spacing.unpack(gutter)
+        self._max_widget_width = 0
+        super().__init__()
+
+    def get_widgets(self, view: View) -> Iterable[Widget]:
+        return view.children
+
+    def arrange(
+        self, view: View, size: Size, scroll: Offset
+    ) -> Iterable[WidgetPlacement]:
+        width, height = size
+        gutter = self.gutter
+        gutter_width = max(gutter.right, gutter.left)
+        x, y = self.gutter.top_left
+
+        for last, widget in loop_last(view.children):
+            styles: Styles = widget.styles
+            render_height = styles.height if styles else height
+            if styles.width:
+                render_width = int(styles.width.resolve_dimension(size, view.app.size))
+            else:
+                render_width = width
+            region = Region(x, y, render_width, render_height)
+            yield WidgetPlacement(region, widget, self.z)
+            x += render_width + (gutter.right if last else gutter_width)

src/textual/layouts/vertical.py

@@ -2,7 +2,6 @@ from __future__ import annotations
 
 from typing import Iterable, TYPE_CHECKING
 
-from textual import log
 from ..css.styles import Styles
 from ..geometry import Offset, Region, Size, Spacing, SpacingDimensions
 from ..layout import Layout, WidgetPlacement

tests/test_view.py

@@ -2,6 +2,7 @@ import pytest
 
 from textual.layouts.dock import DockLayout
 from textual.layouts.grid import GridLayout
+from textual.layouts.horizontal import HorizontalLayout
 from textual.layouts.vertical import VerticalLayout
 from textual.view import View
 
@@ -10,6 +11,7 @@ from textual.view import View
     ["dock", DockLayout],
     ["grid", GridLayout],
     ["vertical", VerticalLayout],
+    ["horizontal", HorizontalLayout],
 ])
 def test_view_layout_get_and_set(layout_name, layout_type):
     view = View()