From 85e3409309e452d45f75c9557f3ad2bf865034ce Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 11:19:32 +0100
Subject: [PATCH 01/10] center layout

---
 sandbox/will/center.py         | 28 ++++++++++++++++++++++++
 src/textual/css/constants.py   |  2 +-
 src/textual/layouts/center.py  | 40 ++++++++++++++++++++++++++++++++++
 src/textual/layouts/factory.py | 10 ++++++---
 src/textual/layouts/grid.py    |  2 ++
 5 files changed, 78 insertions(+), 4 deletions(-)
 create mode 100644 sandbox/will/center.py
 create mode 100644 src/textual/layouts/center.py

diff --git a/sandbox/will/center.py b/sandbox/will/center.py
new file mode 100644
index 000000000..e2941f970
--- /dev/null
+++ b/sandbox/will/center.py
@@ -0,0 +1,28 @@
+from textual.app import App
+from textual.widgets import Static
+
+
+class CenterApp(App):
+    CSS = """
+    
+    Screen {
+        layout: center;
+        overflow: auto auto;
+    }
+
+    Static {
+        border: wide $primary;
+        background: $panel;
+        width: 50;
+        height: 20;
+        margin: 1 2;
+        content-align: center middle;
+    }
+    
+    """
+
+    def compose(self):
+        yield Static("Hello World!")
+
+
+app = CenterApp()
diff --git a/src/textual/css/constants.py b/src/textual/css/constants.py
index 57cfc3201..cf096d98a 100644
--- a/src/textual/css/constants.py
+++ b/src/textual/css/constants.py
@@ -32,7 +32,7 @@ VALID_BORDER: Final[set[EdgeType]] = {
     "wide",
 }
 VALID_EDGE: Final = {"top", "right", "bottom", "left"}
-VALID_LAYOUT: Final = {"vertical", "horizontal"}
+VALID_LAYOUT: Final = {"vertical", "horizontal", "center"}
 
 VALID_BOX_SIZING: Final = {"border-box", "content-box"}
 VALID_OVERFLOW: Final = {"scroll", "hidden", "auto"}
diff --git a/src/textual/layouts/center.py b/src/textual/layouts/center.py
new file mode 100644
index 000000000..813029475
--- /dev/null
+++ b/src/textual/layouts/center.py
@@ -0,0 +1,40 @@
+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
+
+
+class CenterLayout(Layout):
+    """Positions widgets in the center of the screen."""
+
+    name = "center"
+
+    def arrange(
+        self, parent: Widget, children: list[Widget], size: Size
+    ) -> ArrangeResult:
+
+        placements: list[WidgetPlacement] = []
+        total_regions: list[Region] = []
+
+        parent_size = parent.outer_size
+        container_width, container_height = size
+        fraction_unit = Fraction(size.width)
+
+        for widget in children:
+            width, height, margin = widget.get_box_model(
+                size, parent_size, fraction_unit
+            )
+            margin_width = width + margin.width
+            margin_height = height + margin.height
+            x = margin.left + max(0, (container_width - margin_width) // 2)
+            y = margin.top + max(0, (container_height - margin_height) // 2)
+            region = Region(x, y, int(width), int(height))
+            total_regions.append(region.grow(margin))
+            placements.append(WidgetPlacement(region, widget, 0))
+
+        placements.append(WidgetPlacement(Region.from_union(total_regions), None, 0))
+        return placements, set(children)
diff --git a/src/textual/layouts/factory.py b/src/textual/layouts/factory.py
index cc0de2e00..5dd4eae9d 100644
--- a/src/textual/layouts/factory.py
+++ b/src/textual/layouts/factory.py
@@ -1,11 +1,15 @@
-from .horizontal import HorizontalLayout
+from __future__ import annotations
+
 from .._layout import Layout
-from ..layouts.vertical import VerticalLayout
+from .horizontal import HorizontalLayout
+from .vertical import VerticalLayout
+from .center import CenterLayout
 
 
-LAYOUT_MAP = {
+LAYOUT_MAP: dict[str, type[Layout]] = {
     "vertical": VerticalLayout,
     "horizontal": HorizontalLayout,
+    "center": CenterLayout,
 }
 
 
diff --git a/src/textual/layouts/grid.py b/src/textual/layouts/grid.py
index 40526f29a..e2124f804 100644
--- a/src/textual/layouts/grid.py
+++ b/src/textual/layouts/grid.py
@@ -1,3 +1,5 @@
+# TODO: This is deprecated (and probably doesn't work any more)
+
 from __future__ import annotations
 
 import sys

From 5d7a821e1f98f3922576628ca0b9126bd591d85a Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 11:27:33 +0100
Subject: [PATCH 02/10] test for center layout

---
 src/textual/layouts/center.py |  7 +++----
 tests/test_layouts_center.py  | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 4 deletions(-)
 create mode 100644 tests/test_layouts_center.py

diff --git a/src/textual/layouts/center.py b/src/textual/layouts/center.py
index 813029475..164b136ca 100644
--- a/src/textual/layouts/center.py
+++ b/src/textual/layouts/center.py
@@ -1,11 +1,10 @@
 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 ..geometry import Size, Region
+from .._layout import ArrangeResult, Layout, WidgetPlacement
+from ..widget import Widget
 
 
 class CenterLayout(Layout):
diff --git a/tests/test_layouts_center.py b/tests/test_layouts_center.py
new file mode 100644
index 000000000..227f8400e
--- /dev/null
+++ b/tests/test_layouts_center.py
@@ -0,0 +1,33 @@
+from textual.geometry import Region, Size
+from textual.widget import Widget
+from textual.layouts.center import CenterLayout
+from textual._layout import WidgetPlacement
+
+
+def test_center_layout():
+
+    widget = Widget()
+    widget._size = Size(80, 24)
+    child = Widget()
+    child.styles.width = 10
+    child.styles.height = 5
+    layout = CenterLayout()
+
+    placements, widgets = layout.arrange(widget, [child], Size(60, 20))
+    assert widgets == {child}
+
+    expected = [
+        WidgetPlacement(
+            region=Region(x=25, y=7, width=10, height=5),
+            widget=child,
+            order=0,
+            fixed=False,
+        ),
+        WidgetPlacement(
+            region=Region(x=25, y=7, width=10, height=5),
+            widget=None,
+            order=0,
+            fixed=False,
+        ),
+    ]
+    assert placements == expected

From c4f9659c2931df850fc79f680a18048975785cd5 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 14:14:01 +0100
Subject: [PATCH 03/10] imports

---
 src/textual/layouts/center.py | 2 +-
 tests/test_layouts_center.py  | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/textual/layouts/center.py b/src/textual/layouts/center.py
index 164b136ca..e1650f19f 100644
--- a/src/textual/layouts/center.py
+++ b/src/textual/layouts/center.py
@@ -2,8 +2,8 @@ from __future__ import annotations
 
 from fractions import Fraction
 
-from ..geometry import Size, Region
 from .._layout import ArrangeResult, Layout, WidgetPlacement
+from ..geometry import Region, Size
 from ..widget import Widget
 
 
diff --git a/tests/test_layouts_center.py b/tests/test_layouts_center.py
index 227f8400e..52cbd0cc6 100644
--- a/tests/test_layouts_center.py
+++ b/tests/test_layouts_center.py
@@ -1,7 +1,7 @@
-from textual.geometry import Region, Size
-from textual.widget import Widget
-from textual.layouts.center import CenterLayout
 from textual._layout import WidgetPlacement
+from textual.geometry import Region, Size
+from textual.layouts.center import CenterLayout
+from textual.widget import Widget
 
 
 def test_center_layout():

From 76cdea92c6f56e352ab1acc3b45feee169c35a7f Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 14:19:57 +0100
Subject: [PATCH 04/10] capture mouse issue

---
 src/textual/app.py       |  6 +++---
 src/textual/scrollbar.py | 20 ++++++++++++--------
 src/textual/widget.py    |  8 ++++----
 3 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/textual/app.py b/src/textual/app.py
index 18f229e9d..d04573d31 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -680,7 +680,7 @@ class App(Generic[ReturnType], DOMNode):
                 finally:
                     self.mouse_over = widget
 
-    async def capture_mouse(self, widget: Widget | None) -> None:
+    def capture_mouse(self, widget: Widget | None) -> None:
         """Send all mouse events to the given widget, disable mouse capture.
 
         Args:
@@ -689,12 +689,12 @@ class App(Generic[ReturnType], DOMNode):
         if widget == self.mouse_captured:
             return
         if self.mouse_captured is not None:
-            await self.mouse_captured.post_message(
+            self.mouse_captured.post_message_no_wait(
                 events.MouseRelease(self, self.mouse_position)
             )
         self.mouse_captured = widget
         if widget is not None:
-            await widget.post_message(events.MouseCapture(self, self.mouse_position))
+            widget.post_message_no_wait(events.MouseCapture(self, self.mouse_position))
 
     def panic(self, *renderables: RenderableType) -> None:
         """Exits the app then displays a message.
diff --git a/src/textual/scrollbar.py b/src/textual/scrollbar.py
index d70faca32..bd9545982 100644
--- a/src/textual/scrollbar.py
+++ b/src/textual/scrollbar.py
@@ -231,10 +231,14 @@ class ScrollBar(Widget):
             style=scrollbar_style,
         )
 
-    async def on_enter(self, event: events.Enter) -> None:
+    def on_hide(self, event: events.Hide) -> None:
+        if self.grabbed:
+            self.release_mouse()
+
+    def on_enter(self, event: events.Enter) -> None:
         self.mouse_over = True
 
-    async def on_leave(self, event: events.Leave) -> None:
+    def on_leave(self, event: events.Leave) -> None:
         self.mouse_over = False
 
     async def action_scroll_down(self) -> None:
@@ -243,15 +247,15 @@ class ScrollBar(Widget):
     async def action_scroll_up(self) -> None:
         await self.emit(ScrollUp(self) if self.vertical else ScrollLeft(self))
 
-    async def action_grab(self) -> None:
-        await self.capture_mouse()
+    def action_grab(self) -> None:
+        self.capture_mouse()
 
-    async def action_released(self) -> None:
-        await self.capture_mouse(False)
+    def action_released(self) -> None:
+        self.capture_mouse(False)
 
-    async def on_mouse_up(self, event: events.MouseUp) -> None:
+    def on_mouse_up(self, event: events.MouseUp) -> None:
         if self.grabbed:
-            await self.release_mouse()
+            self.release_mouse()
 
     async def on_mouse_capture(self, event: events.MouseCapture) -> None:
         self.grabbed = event.mouse_position
diff --git a/src/textual/widget.py b/src/textual/widget.py
index d1f218bc2..1f7eca0e3 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -1090,7 +1090,7 @@ class Widget(DOMNode):
         """Give input focus to this widget."""
         self.app.set_focus(self)
 
-    async def capture_mouse(self, capture: bool = True) -> None:
+    def capture_mouse(self, capture: bool = True) -> None:
         """Capture (or release) the mouse.
 
         When captured, all mouse coordinates will go to this widget even when the pointer is not directly over the widget.
@@ -1098,14 +1098,14 @@ class Widget(DOMNode):
         Args:
             capture (bool, optional): True to capture or False to release. Defaults to True.
         """
-        await self.app.capture_mouse(self if capture else None)
+        self.app.capture_mouse(self if capture else None)
 
-    async def release_mouse(self) -> None:
+    def release_mouse(self) -> None:
         """Release the mouse.
 
         Mouse events will only be sent when the mouse is over the widget.
         """
-        await self.app.capture_mouse(None)
+        self.app.capture_mouse(None)
 
     async def broker_event(self, event_name: str, event: events.Event) -> bool:
         return await self.app.broker_event(event_name, event, default_namespace=self)

From b8bc41fafebdbceb24e2a2f43e787b24b7e526e6 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 14:23:31 +0100
Subject: [PATCH 05/10] async tweak

---
 src/textual/scrollbar.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/textual/scrollbar.py b/src/textual/scrollbar.py
index bd9545982..d13c502f8 100644
--- a/src/textual/scrollbar.py
+++ b/src/textual/scrollbar.py
@@ -235,10 +235,10 @@ class ScrollBar(Widget):
         if self.grabbed:
             self.release_mouse()
 
-    def on_enter(self, event: events.Enter) -> None:
+    async def on_enter(self, event: events.Enter) -> None:
         self.mouse_over = True
 
-    def on_leave(self, event: events.Leave) -> None:
+    async def on_leave(self, event: events.Leave) -> None:
         self.mouse_over = False
 
     async def action_scroll_down(self) -> None:
@@ -253,15 +253,15 @@ class ScrollBar(Widget):
     def action_released(self) -> None:
         self.capture_mouse(False)
 
-    def on_mouse_up(self, event: events.MouseUp) -> None:
+    async def on_mouse_up(self, event: events.MouseUp) -> None:
         if self.grabbed:
             self.release_mouse()
 
-    async def on_mouse_capture(self, event: events.MouseCapture) -> None:
+    def on_mouse_capture(self, event: events.MouseCapture) -> None:
         self.grabbed = event.mouse_position
         self.grabbed_position = self.position
 
-    async def on_mouse_release(self, event: events.MouseRelease) -> None:
+    def on_mouse_release(self, event: events.MouseRelease) -> None:
         self.grabbed = None
 
     async def on_mouse_move(self, event: events.MouseMove) -> None:

From e7cfe88b02f67305b24822a74dcf62d53559ac32 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 14:26:05 +0100
Subject: [PATCH 06/10] events signature

---
 src/textual/scrollbar.py | 4 ++--
 src/textual/widget.py    | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/textual/scrollbar.py b/src/textual/scrollbar.py
index d13c502f8..ea5d510dd 100644
--- a/src/textual/scrollbar.py
+++ b/src/textual/scrollbar.py
@@ -235,10 +235,10 @@ class ScrollBar(Widget):
         if self.grabbed:
             self.release_mouse()
 
-    async def on_enter(self, event: events.Enter) -> None:
+    def on_enter(self, event: events.Enter) -> None:
         self.mouse_over = True
 
-    async def on_leave(self, event: events.Leave) -> None:
+    def on_leave(self, event: events.Leave) -> None:
         self.mouse_over = False
 
     async def action_scroll_down(self) -> None:
diff --git a/src/textual/widget.py b/src/textual/widget.py
index 1f7eca0e3..69886f6ab 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -1128,10 +1128,10 @@ class Widget(DOMNode):
             self.mount(*widgets)
             self.screen.refresh(repaint=False, layout=True)
 
-    def on_leave(self) -> None:
+    def on_leave(self, event: events.Leave) -> None:
         self.mouse_over = False
 
-    def on_enter(self) -> None:
+    def on_enter(self, event: events.Enter) -> None:
         self.mouse_over = True
 
     def on_focus(self, event: events.Focus) -> None:

From 2a8504973280946de32eaa769c764358467bc845 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 15:00:21 +0100
Subject: [PATCH 07/10] added center layout

---
 sandbox/will/center2.py | 48 +++++++++++++++++++++++++++++++++++++++++
 src/textual/layout.py   | 12 +++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 sandbox/will/center2.py

diff --git a/sandbox/will/center2.py b/sandbox/will/center2.py
new file mode 100644
index 000000000..e4d78ac25
--- /dev/null
+++ b/sandbox/will/center2.py
@@ -0,0 +1,48 @@
+from textual.app import App
+from textual.layout import Vertical, Center
+from textual.widgets import Static
+
+
+class CenterApp(App):
+    CSS = """
+
+    #sidebar {
+        dock: left;
+        width: 32;
+        height: 100%;
+        border-right: vkey $primary;
+    }
+
+    #bottombar {
+        dock: bottom;
+        height: 12;
+        width: 100%;
+        border-top: hkey $primary;
+    }
+
+    #hello {
+        border: wide $primary;
+        width: 40;
+        height: 16;      
+        margin: 2 4;  
+    }
+
+    Static {        
+        background: $panel;
+        color: $text-panel;
+        content-align: center middle;
+    }
+    
+    """
+
+    def compose(self):
+        yield Static("Sidebar", id="sidebar")
+        yield Vertical(
+            Static("Bottom bar", id="bottombar"),
+            Center(
+                Static("Hello World!", id="hello"),
+            ),
+        )
+
+
+app = CenterApp()
diff --git a/src/textual/layout.py b/src/textual/layout.py
index 82db0e7da..597dd5326 100644
--- a/src/textual/layout.py
+++ b/src/textual/layout.py
@@ -21,3 +21,15 @@ class Horizontal(Widget):
         overflow: auto;
     }    
     """
+
+
+class Center(Widget):
+    """A container widget to align children in the center."""
+
+    CSS = """
+    Center {
+        layout: center;
+        overflow: auto;
+    }
+    
+    """

From c4ac2cce95de4c11ec93936265b8b7abbe054f24 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 21:03:16 +0100
Subject: [PATCH 08/10] layout hierarchy

---
 src/textual/layout.py | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/textual/layout.py b/src/textual/layout.py
index 597dd5326..c4b64bcbd 100644
--- a/src/textual/layout.py
+++ b/src/textual/layout.py
@@ -1,35 +1,37 @@
 from .widget import Widget
 
 
-class Vertical(Widget):
-    """A container widget to align children vertically."""
+class Container(Widget):
+    """Simple container widget, with vertical layout."""
 
     CSS = """
-    Vertical {
+    Container {
         layout: vertical;       
         overflow: auto;
     }    
     """
 
 
-class Horizontal(Widget):
+class Vertical(Container):
+    """A container widget to align children vertically."""
+
+
+class Horizontal(Container):
     """A container widget to align children horizontally."""
 
     CSS = """
     Horizontal {
-        layout: horizontal;
-        overflow: auto;
+        layout: horizontal;        
     }    
     """
 
 
-class Center(Widget):
+class Center(Container):
     """A container widget to align children in the center."""
 
     CSS = """
     Center {
-        layout: center;
-        overflow: auto;
+        layout: center;        
     }
     
     """

From f9828fba715311cc3ec1ac591833e8392aa014d2 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Sun, 7 Aug 2022 21:16:59 +0100
Subject: [PATCH 09/10] fix bug with layout updates

---
 sandbox/will/center2.py    | 9 ++++++++-
 src/textual/_compositor.py | 1 +
 src/textual/box_model.py   | 2 +-
 src/textual/screen.py      | 1 -
 src/textual/widget.py      | 4 +++-
 5 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/sandbox/will/center2.py b/sandbox/will/center2.py
index e4d78ac25..1711fd09a 100644
--- a/sandbox/will/center2.py
+++ b/sandbox/will/center2.py
@@ -27,6 +27,10 @@ class CenterApp(App):
         margin: 2 4;  
     }
 
+    #sidebar.hidden {
+       width: 0;
+    }
+
     Static {        
         background: $panel;
         color: $text-panel;
@@ -35,6 +39,9 @@ class CenterApp(App):
     
     """
 
+    def on_mount(self) -> None:
+        self.bind("t", "toggle_class('#sidebar', 'hidden')")
+
     def compose(self):
         yield Static("Sidebar", id="sidebar")
         yield Vertical(
@@ -45,4 +52,4 @@ class CenterApp(App):
         )
 
 
-app = CenterApp()
+app = CenterApp(log_verbosity=3)
diff --git a/src/textual/_compositor.py b/src/textual/_compositor.py
index 72b309d89..1de9e67f3 100644
--- a/src/textual/_compositor.py
+++ b/src/textual/_compositor.py
@@ -632,6 +632,7 @@ class Compositor:
             update_regions: set[Region] = set()
         else:
             update_regions = self._dirty_regions.copy()
+
             if screen_region in update_regions:
                 # If one of the updates is the entire screen, then we only need one update
                 full = True
diff --git a/src/textual/box_model.py b/src/textual/box_model.py
index 3d7a9a6cd..e05ace9e3 100644
--- a/src/textual/box_model.py
+++ b/src/textual/box_model.py
@@ -81,7 +81,7 @@ def get_box_model(
         )
         content_width = min(content_width, max_width)
 
-    content_width = max(Fraction(1), content_width)
+    content_width = max(Fraction(0), content_width)
 
     if styles.height is None:
         # No height specified, fill the available space
diff --git a/src/textual/screen.py b/src/textual/screen.py
index 2af611482..c4773b76e 100644
--- a/src/textual/screen.py
+++ b/src/textual/screen.py
@@ -170,7 +170,6 @@ class Screen(Widget):
         self.update_timer.pause()
         try:
             hidden, shown, resized = self._compositor.reflow(self, size)
-
             Hide = events.Hide
             Show = events.Show
             for widget in hidden:
diff --git a/src/textual/widget.py b/src/textual/widget.py
index 69886f6ab..558733c8d 100644
--- a/src/textual/widget.py
+++ b/src/textual/widget.py
@@ -1040,7 +1040,9 @@ class Widget(DOMNode):
 
         if layout:
             self._layout_required = True
-            self._clear_arrangement_cache()
+            if isinstance(self._parent, Widget):
+                self._parent._clear_arrangement_cache()
+
         if repaint:
             self._set_dirty(*regions)
             self._content_width_cache = (None, 0)

From a4e0a43273b443cc1f359031b4c7910d227a0105 Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Mon, 8 Aug 2022 17:44:36 +0100
Subject: [PATCH 10/10] superfluous space

---
 src/textual/_compositor.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/textual/_compositor.py b/src/textual/_compositor.py
index 1de9e67f3..72b309d89 100644
--- a/src/textual/_compositor.py
+++ b/src/textual/_compositor.py
@@ -632,7 +632,6 @@ class Compositor:
             update_regions: set[Region] = set()
         else:
             update_regions = self._dirty_regions.copy()
-
             if screen_region in update_regions:
                 # If one of the updates is the entire screen, then we only need one update
                 full = True