eof

src/textual/css/_style_properties.py

@@ -8,7 +8,7 @@ from rich.style import Style
 
 from ..geometry import Offset, Spacing, SpacingDimensions
 from .constants import NULL_SPACING, VALID_EDGE
-from .errors import StyleValueError
+from .errors import StyleTypeError, StyleValueError
 from ._error_tools import friendly_list
 
 if TYPE_CHECKING:
@@ -215,12 +215,15 @@ class DockEdgeProperty:
 
 class IntegerProperty:
     def __set_name__(self, owner: Styles, name: str) -> None:
+        self._name = name
         self._internal_name = f"_{name}"
 
     def __get__(self, obj: Styles, objtype: type[Styles] | None = None) -> int:
         return getattr(obj, self._internal_name, 0)
 
     def __set__(self, obj: Styles, value: int | None) -> int | None:
+        if not isinstance(value, int):
+            raise StyleTypeError(f"{self._name} must be a str")
         setattr(obj, self._internal_name, value)
         return value
 
@@ -235,7 +238,7 @@ class StringProperty:
         self._internal_name = f"_{name}"
 
     def __get__(self, obj: Styles, objtype: type[Styles] | None = None) -> str:
-        return getattr(obj, self._internal_name, self._default)
+        return getattr(obj, self._internal_name, None) or self._default
 
     def __set__(self, obj: Styles, value: str | None = None) -> str | None:
         if value is not None:
@@ -245,3 +248,42 @@ class StringProperty:
                 )
         setattr(obj, self._internal_name, value)
         return value
+
+
+class NameProperty:
+    def __set_name__(self, owner: Styles, name: str) -> None:
+        self._name = name
+        self._internal_name = f"_{name}"
+
+    def __get__(self, obj: Styles, objtype: type[Styles] | None) -> str:
+        return getattr(obj, self._internal_name, None) or ""
+
+    def __set__(self, obj: Styles, name: str | None) -> str | None:
+        if not isinstance(name, str):
+            raise StyleTypeError(f"{self._name} must be a str")
+        setattr(obj, self._internal_name, name)
+        return name
+
+
+class NameListProperty:
+    def __set_name__(self, owner: Styles, name: str) -> None:
+        self._name = name
+        self._internal_name = f"_{name}"
+
+    def __get__(
+        self, obj: Styles, objtype: type[Styles] | None = None
+    ) -> tuple[str, ...]:
+        return getattr(obj, self._internal_name, None) or ()
+
+    def __set__(
+        self, obj: Styles, names: str | tuple[str] | None = None
+    ) -> str | tuple[str] | None:
+        names_value: tuple[str, ...] | None = None
+        if isinstance(names, str):
+            names_value = tuple(name.strip().lower() for name in names.split(" "))
+        elif isinstance(names, tuple):
+            names_value = names
+        elif names is None:
+            names_value = None
+        setattr(obj, self._internal_name, names_value)
+        return names

src/textual/css/errors.py

@@ -7,6 +7,10 @@ class DeclarationError(Exception):
         super().__init__(message)
 
 
+class StyleTypeError(TypeError):
+    pass
+
+
 class StyleValueError(ValueError):
     pass
 

src/textual/css/example.css

@@ -1,26 +1,23 @@
-
 view.buttons {
-    layout: dock
+  layout: dock;
 }
 
 .buttons .button {
-    dock: top
-    size: 10px
+  dock: top;
+  size: 10px;
 }
 
-
 #widget {
-    visibility: visible;
-    text-style: bold;
+  visibility: visible;
+  text-style: bold;
 
-    border: dashed !important;
-    border-top: dashed green;
-    border-bottom: red;
+  border: dashed !important;
+  border-top: dashed green;
+  border-bottom: red;
 
-    padding: 1 0;
-    margin: 1;
-
-    layout: dock
-    dock-edge: left;
+  padding: 1 0;
+  margin: 1;
 
+  layout: dock;
+  dock-edge: left;
 }

src/textual/css/styles.py

@@ -23,6 +23,8 @@ from ._style_properties import (
     DockGroupProperty,
     IntegerProperty,
     OffsetProperty,
+    NameProperty,
+    NameListProperty,
     SpacingProperty,
     StringProperty,
     StyleProperty,
@@ -61,6 +63,9 @@ class Styles:
     _dock_edge: str | None = None
     _docks: tuple[str, ...] | None = None
 
+    _layers: str | None = None
+    _layer: tuple[str, ...] | None = None
+
     important: set[str] = field(default_factory=set)
 
     display = StringProperty(VALID_DISPLAY, "block")
@@ -93,6 +98,9 @@ class Styles:
     docks = DocksProperty()
     dock_edge = DockEdgeProperty()
 
+    layer = NameProperty()
+    layers = NameListProperty()
+
     @property
     def has_border(self) -> bool:
         """Check in a border is present."""
@@ -117,6 +125,8 @@ class Styles:
         yield "padding", self.padding, NULL_SPACING
         yield "text", self.text, ""
         yield "visibility", self.visibility, "visible"
+        yield "layers", self.layers, ()
+        yield "layer", self.layer, ""
 
         if self.important:
             yield "important", self.important
@@ -196,6 +206,11 @@ class Styles:
             append_declaration("docks", " ".join(self._docks))
         if self._dock_edge:
             append_declaration("dock-edge", self._dock_edge)
+        if self._layers is not None:
+            append_declaration("layers", " ".join(self.layers))
+        if self._layer is not None:
+            append_declaration("layer", self.layer)
+
         lines.sort()
         return lines
 
@@ -214,6 +229,7 @@ if __name__ == "__main__":
     styles.docks = "foo bar"
     styles.text = "italic blue"
     styles.dock_group = "bar"
+    styles.layers = "foo bar"
 
     from rich import inspect, print
 

src/textual/layouts/grid.py

@@ -6,18 +6,25 @@ from operator import itemgetter
 from logging import getLogger
 from itertools import cycle, product
 import sys
-from typing import Iterable, NamedTuple
+from typing import Iterable, NamedTuple, TYPE_CHECKING
 
 from .._layout_resolve import layout_resolve
 from ..geometry import Size, Offset, Region
 from ..layout import Layout, WidgetPlacement
 from ..widget import Widget
 
+
+if TYPE_CHECKING:
+    from ..widget import Widget
+    from ..view import View
+
+
 if sys.version_info >= (3, 8):
     from typing import Literal
 else:
     from typing_extensions import Literal
 
+
 log = getLogger("rich")
 
 GridAlign = Literal["start", "end", "center", "stretch"]

src/textual/layouts/vertical.py

@@ -1,12 +1,16 @@
 from __future__ import annotations
 
-from typing import Iterable
+from typing import Iterable, TYPE_CHECKING
 
 from ..geometry import Offset, Region, Size, Spacing, SpacingDimensions
 from ..layout import Layout, WidgetPlacement
 from ..widget import Widget
 from .._loop import loop_last
 
+if TYPE_CHECKING:
+    from ..widget import Widget
+    from ..view import View
+
 
 class VerticalLayout(Layout):
     def __init__(