grid align

examples/calculator.py

@@ -0,0 +1,42 @@
+from textual.app import App
+from textual import events
+from textual.view import View
+from textual.widgets import Placeholder
+from textual.layouts.grid import GridLayout
+
+
+class GridTest(App):
+    async def on_load(self, event: events.Load) -> None:
+        await self.bind("q,ctrl+c", "quit", "Quit")
+
+    async def on_startup(self, event: events.Startup) -> None:
+
+        layout = GridLayout()
+        view = await self.push_view(View(layout=layout))
+
+        layout.add_column(name="col1", max_size=20)
+        layout.add_column(name="col2", max_size=20)
+        layout.add_column(name="col3", max_size=20)
+        layout.add_column(name="col4", max_size=20)
+
+        layout.add_row(name="numbers", max_size=10)
+        layout.add_row(name="row1", max_size=10)
+        layout.add_row(name="row2", max_size=10)
+        layout.add_row(name="row3", max_size=10)
+        layout.add_row(name="row4", max_size=10)
+
+        layout.add_area("numbers", ("col1-start", "col4-end"), "numbers")
+        layout.add_area("zero", ("col1-start", "col2-end"), "row4")
+        layout.add_area("dot", "col3", "row4")
+        layout.add_area("equals", "col4", "row4")
+
+        layout.add_widget(Placeholder(name="numbers"), area="numbers")
+        layout.add_widget(Placeholder(name="0"), area="zero")
+        layout.add_widget(Placeholder(name="."), area="dot")
+        layout.add_widget(Placeholder(name="="), area="equals")
+
+        layout.set_gap(1)
+        layout.set_align("center", "center")
+
+
+GridTest.run(title="Calculator Test")

examples/grid.py

@@ -14,7 +14,7 @@ class GridTest(App):
         layout = GridLayout()
         view = await self.push_view(View(layout=layout))
 
-        layout.add_column(fraction=1, name="left", minimum_size=20)
+        layout.add_column(fraction=1, name="left", min_size=20)
         layout.add_column(size=30, name="center")
         layout.add_column(fraction=1, name="right")
 

src/textual/_layout_resolve.py

@@ -0,0 +1,79 @@
+from __future__ import annotations
+
+import sys
+from fractions import Fraction
+from typing import cast, List, Optional, Sequence
+
+if sys.version_info >= (3, 8):
+    from typing import Protocol
+else:
+    from typing_extensions import Protocol  # pragma: no cover
+
+
+class Edge(Protocol):
+    """Any object that defines an edge (such as Layout)."""
+
+    size: Optional[int] = None
+    fraction: int = 1
+    min_size: int = 1
+
+
+def layout_resolve(total: int, edges: Sequence[Edge]) -> List[int]:
+    """Divide total space to satisfy size, ratio, and minimum_size, constraints.
+
+    The returned list of integers should add up to total in most cases, unless it is
+    impossible to satisfy all the constraints. For instance, if there are two edges
+    with a minimum size of 20 each and `total` is 30 then the returned list will be
+    greater than total. In practice, this would mean that a Layout object would
+    clip the rows that would overflow the screen height.
+
+    Args:
+        total (int): Total number of characters.
+        edges (List[Edge]): Edges within total space.
+
+    Returns:
+        List[int]: Number of characters for each edge.
+    """
+    # Size of edge or None for yet to be determined
+    sizes = [(edge.size or None) for edge in edges]
+
+    _Fraction = Fraction
+
+    # While any edges haven't been calculated
+    while None in sizes:
+        # Get flexible edges and index to map these back on to sizes list
+        flexible_edges = [
+            (index, edge)
+            for index, (size, edge) in enumerate(zip(sizes, edges))
+            if size is None
+        ]
+        # Remaining space in total
+        remaining = total - sum(size or 0 for size in sizes)
+        if remaining <= 0:
+            # No room for flexible edges
+            return [
+                ((edge.min_size or 1) if size is None else size)
+                for size, edge in zip(sizes, edges)
+            ]
+        # Calculate number of characters in a ratio portion
+        portion = _Fraction(
+            remaining, sum((edge.fraction or 1) for _, edge in flexible_edges)
+        )
+
+        # If any edges will be less than their minimum, replace size with the minimum
+        for index, edge in flexible_edges:
+            if portion * edge.fraction <= edge.min_size:
+                sizes[index] = edge.min_size
+                # New fixed size will invalidate calculations, so we need to repeat the process
+                break
+        else:
+            # Distribute flexible space and compensate for rounding error
+            # Since edge sizes can only be integers we need to add the remainder
+            # to the following line
+            remainder = _Fraction(0)
+            for index, edge in flexible_edges:
+                size, remainder = divmod(portion * edge.fraction + remainder, 1)
+                sizes[index] = size
+            break
+    # Sizes now contains integers only
+    return cast(List[int], sizes)

src/textual/layouts/grid.py

@@ -1,21 +1,32 @@
 from __future__ import annotations
 
+from collections import defaultdict
 from dataclasses import dataclass
+from itertools import cycle
+import sys
 from typing import Iterable, NamedTuple
 
 from .._layout_resolve import layout_resolve
 from .._loop import loop_last
-from ..geometry import Point, Region
+from ..geometry import Dimensions, Point, Region
 from ..layout import Layout, OrderedRegion
 from ..widget import Widget
 
+if sys.version_info >= (3, 8):
+    from typing import Literal
+else:
+    from typing_extensions import Literal
+
+
+GridAlign = Literal["start", "end", "center", "stretch"]
+
 
 @dataclass
 class GridOptions:
     size: int | None = None
     fraction: int = 1
-    minimum_size: int = 1
+    min_size: int = 1
-    maximum_size: int | None = None
+    max_size: int | None = None
     name: str | None = None
 
 
@@ -34,6 +45,11 @@ class GridLayout(Layout):
         self.widgets: dict[Widget, str | None] = {}
         self.column_gap = 1
         self.row_gap = 1
+        self.column_repeat = False
+        self.row_repeat = False
+        self.column_align: GridAlign = "start"
+        self.row_align: GridAlign = "start"
+
         super().__init__()
 
     def add_column(
@@ -41,11 +57,16 @@ class GridLayout(Layout):
         *,
         size: int | None = None,
         fraction: int = 1,
-        minimum_size: int = 1,
+        min_size: int = 1,
+        max_size: int | None = None,
         name: str | None = None,
     ) -> None:
         options = GridOptions(
-            size=size, fraction=fraction, minimum_size=minimum_size, name=name
+            size=size,
+            fraction=fraction,
+            min_size=min_size,
+            max_size=max_size,
+            name=name,
         )
         self.columns.append(options)
 
@@ -54,11 +75,16 @@ class GridLayout(Layout):
         *,
         size: int | None = None,
         fraction: int = 1,
-        minimum_size: int = 1,
+        min_size: int = 1,
+        max_size: int | None = None,
         name: str | None = None,
     ) -> None:
         options = GridOptions(
-            size=size, fraction=fraction, minimum_size=minimum_size, name=name
+            size=size,
+            fraction=fraction,
+            min_size=min_size,
+            max_size=max_size,
+            name=name,
         )
         self.rows.append(options)
 
@@ -80,7 +106,7 @@ class GridLayout(Layout):
         area = GridArea(column_start, column_end, row_start, row_end)
         self.areas[name] = area
 
-    def set_gaps(self, column: int, row: int | None) -> None:
+    def set_gap(self, column: int, row: int | None = None) -> None:
         self.column_gap = column
         self.row_gap = column if row is None else row
 
@@ -88,36 +114,87 @@ class GridLayout(Layout):
         self.widgets[widget] = area
         return widget
 
+    def set_repeat(self, column: bool | None = None, row: bool | None = None) -> None:
+        if column is not None:
+            self.column_repeat = column
+        if row is not None:
+            self.row_repeat = row
+
+    def set_align(self, column: GridAlign | None = None, row: GridAlign | None = None):
+        if column is not None:
+            self.column_align = column
+        if row is not None:
+            self.row_align = row
+
+    @classmethod
+    def _align(
+        cls,
+        region: Region,
+        grid_size: Dimensions,
+        container: Dimensions,
+        col_align: GridAlign,
+        row_align: GridAlign,
+    ) -> Region:
+        offset_x = 0
+        offset_y = 0
+
+        def align(size: int, container: int, align: GridAlign) -> int:
+            offset = 0
+            if align == "end":
+                offset = container - size
+            elif align == "center":
+                offset = (container - size) // 2
+            return offset
+
+        size = region.size
+        offset_x = align(grid_size.width, container.width, col_align)
+        offset_y = align(grid_size.height, container.height, row_align)
+
+        region = region.translate(offset_x, offset_y)
+        return region
+
     def generate_map(
         self, width: int, height: int, offset: Point = Point(0, 0)
     ) -> dict[Widget, OrderedRegion]:
         def resolve(
-            size: int, edges: list[GridOptions], gap: int
+            size: int, edges: list[GridOptions], gap: int, repeat: bool
         ) -> Iterable[tuple[int, int]]:
             tracks = [
-                track if edge.maximum_size is None else min(edge.maximum_size, track)
+                track if edge.max_size is None else min(edge.max_size, track)
                 for track, edge in zip(layout_resolve(size, edges), edges)
             ]
+            if repeat:
+                tracks = cycle(tracks)
             total = 0
-            for last, track in loop_last(tracks):
+            for index, track in enumerate(tracks):
-                yield total, total + track if last else total + track - gap
+                yield total, total + track - gap if total + track < size else total + track
                 total += track
+                if total >= size and index >= len(edges):
+                    break
 
         def resolve_tracks(
-            grid: list[GridOptions], size: int, gap: int
+            grid: list[GridOptions], size: int, gap: int, repeat: bool
-        ) -> dict[str, int]:
+        ) -> tuple[dict[str, list[int]], int]:
             spans = (
                 (options.name, span)
-                for options, span in zip(grid, resolve(size, grid, gap))
+                for options, span in zip(cycle(grid), resolve(size, grid, gap, repeat))
             )
-            tracks: dict[str, int] = {}
+            max_size = 0
+            tracks: dict[str, list[int]] = defaultdict(list)
             for name, (start, end) in spans:
-                tracks[f"{name}-start"] = start
+                max_size = max(max_size, end)
-                tracks[f"{name}-end"] = end
+                tracks[f"{name}-start"].append(start)
-            return tracks
+                tracks[f"{name}-end"].append(end)
+            return tracks, max_size
 
-        column_tracks = resolve_tracks(self.columns, width, self.column_gap)
+        column_tracks, column_size = resolve_tracks(
-        row_tracks = resolve_tracks(self.rows, height, self.row_gap)
+            self.columns, width, self.column_gap, self.column_repeat
+        )
+        row_tracks, row_size = resolve_tracks(
+            self.rows, height, self.row_gap, self.row_repeat
+        )
+        container_size = Dimensions(width, height)
+        grid_size = Dimensions(column_size, row_size)
 
         widget_areas = (
             (widget, area)
@@ -130,31 +207,38 @@ class GridLayout(Layout):
         from_corners = Region.from_corners
         for widget, area in widget_areas:
             column_start, column_end, row_start, row_end = self.areas[area]
-            x1 = column_tracks[column_start]
+            try:
-            x2 = column_tracks[column_end]
+                x1 = column_tracks[column_start][0]
-            y1 = row_tracks[row_start]
+                x2 = column_tracks[column_end][0]
-            y2 = row_tracks[row_end]
+                y1 = row_tracks[row_start][0]
-            map[widget] = OrderedRegion(from_corners(x1, y1, x2, y2), (0, order))
+                y2 = row_tracks[row_end][0]
+            except (KeyError, IndexError):
+                continue
+
+            region = from_corners(x1, y1, x2, y2)
+            region = self._align(
+                region, grid_size, container_size, self.column_align, self.row_align
+            )
+            map[widget] = OrderedRegion(region, (0, order))
             order += 1
 
+        # Widgets with no area assigned.
+        auto_widgets = [widget for widget, area in self.widgets.items() if area is None]
+
         return map
 
 
 if __name__ == "__main__":
     layout = GridLayout()
-    layout.add_column(size=20, name="left")
+
-    layout.add_column(fraction=2, name="middle")
+    layout.add_column(size=20, name="a")
-    layout.add_column(fraction=1, name="right")
+    layout.add_column(size=10, name="b")
 
     layout.add_row(fraction=1, name="top")
     layout.add_row(fraction=2, name="bottom")
 
     layout.add_area("center", "middle", "top")
 
-    from ..widgets import Static
-
-    layout.add_widget(Static("foo"), "center")
-
     from rich import print
 
     print(layout.widgets)

src/textual/view.py

@@ -105,6 +105,8 @@ class View(Widget):
         send_resize = shown
         send_resize.update(resized)
         for widget, region in self.layout:
+            if not self.is_mounted(widget):
+                await self.mount(widget)
             if widget in send_resize:
                 widget.post_message_no_wait(
                     events.Resize(self, region.width, region.height)