scalar resolve

src/textual/css/_style_properties.py

@@ -18,8 +18,11 @@ if TYPE_CHECKING:
 
 
 class ScalarProperty:
-    def __init__(self, units: set[Unit] | None = None) -> None:
+    def __init__(
+        self, units: set[Unit] | None = None, percent_unit: Unit = Unit.WIDTH
+    ) -> None:
         self.units: set[Unit] = units or {*UNIT_SYMBOL}
+        self.percent_unit = percent_unit
         super().__init__()
 
     def __set_name__(self, owner: Styles, name: str) -> None:
@@ -53,6 +56,8 @@ class ScalarProperty:
             raise StyleValueError(
                 f"{self.name} units must be one of {friendly_list(get_symbols(self.units))}"
             )
+        if new_value is not None and new_value.is_percent:
+            new_value = Scalar(new_value.value, self.percent_unit)
         setattr(obj, self.internal_name, new_value)
         return value
 

src/textual/css/_styles_builder.py

@@ -94,7 +94,7 @@ class StylesBuilder:
 
     def process_visibility(self, name: str, tokens: list[Token]) -> None:
         for token in tokens:
-            _, _, location, name, value = token
+            name, value, _, _, location = token
             if name == "token":
                 value = value.lower()
                 if value in VALID_VISIBILITY:
@@ -114,12 +114,15 @@ class StylesBuilder:
         for token in tokens:
             (token_name, value, _, _, location) = token
             if token_name == "scalar":
-                append(int(value))
+                try:
+                    append(int(value))
+                except ValueError:
+                    self.error(name, token, f"expected a number here; found {value!r}")
             else:
                 self.error(name, token, f"unexpected token {value!r} in declaration")
         if len(space) not in (1, 2, 4):
             self.error(
-                name, tokens[0], f"1, 2, or 4 values expected (received {len(space)})"
+                name, tokens[0], f"1, 2, or 4 values expected; received {len(space)}"
             )
         setattr(
             self.styles,

src/textual/css/scalar.py

@@ -4,6 +4,18 @@ from enum import Enum, unique
 import re
 from typing import Iterable, NamedTuple
 
+import rich.repr
+
+from ..geometry import Offset
+
+
+class ScalarResolveError(Exception):
+    pass
+
+
+class ScalarParseError(Exception):
+    pass
+
 
 @unique
 class Unit(Enum):
@@ -31,6 +43,15 @@ SYMBOL_UNIT = {v: k for k, v in UNIT_SYMBOL.items()}
 _MATCH_SCALAR = re.compile(r"^(\d+\.?\d*)(fr|%|w|h|vw|vh)?$").match
 
 
+RESOLVE_MAP = {
+    Unit.CELLS: lambda value, size, viewport: value,
+    Unit.WIDTH: lambda value, size, viewport: size[0],
+    Unit.HEIGHT: lambda value, size, viewport: size[1],
+    Unit.VIEW_WIDTH: lambda value, size, viewport: viewport[0],
+    Unit.VIEW_HEIGHT: lambda value, size, viewport: viewport[1],
+}
+
+
 def get_symbols(units: Iterable[Unit]) -> list[str]:
     """Get symbols for an iterable of units.
 
@@ -43,10 +64,6 @@ def get_symbols(units: Iterable[Unit]) -> list[str]:
     return [UNIT_SYMBOL[unit] for unit in units]
 
 
-class ScalarParseError(Exception):
-    pass
-
-
 class Scalar(NamedTuple):
     """A numeric value and a unit."""
 
@@ -57,6 +74,10 @@ class Scalar(NamedTuple):
         value, _unit = self
         return f"{int(value) if value.is_integer() else value}{self.symbol}"
 
+    @property
+    def is_percent(self) -> bool:
+        return self.unit == Unit.PERCENT
+
     @property
     def cells(self) -> int | None:
         value, unit = self
@@ -91,6 +112,37 @@ class Scalar(NamedTuple):
         scalar = cls(float(value), SYMBOL_UNIT[unit_name or ""])
         return scalar
 
+    def resolve(
+        self,
+        size: tuple[int, int],
+        viewport: tuple[int, int],
+        percent_unit: Unit = Unit.WIDTH,
+    ) -> float:
+        value, unit = self
+        if unit == Unit.PERCENT:
+            unit = percent_unit
+        try:
+            return RESOLVE_MAP[unit](value, size, viewport)
+        except KeyError:
+            raise ScalarResolveError("unable to resolve {self!r}")
+
+
+@rich.repr.auto(angular=True)
+class ScalarOffset(NamedTuple):
+    x: Scalar
+    y: Scalar
+
+    def __rich_repr__(self) -> rich.repr.Result:
+        yield str(self.x)
+        yield str(self.y)
+
+    def resolve(self, size: tuple[int, int], viewport: tuple[int, int]) -> Offset:
+        x, y = self
+        return Offset(
+            round(x.resolve(size, viewport, percent_unit=Unit.WIDTH)),
+            round(y.resolve(size, viewport, percent_unit=Unit.HEIGHT)),
+        )
+
 
 if __name__ == "__main__":
 

src/textual/css/styles.py

@@ -18,7 +18,7 @@ from .constants import (
     NULL_SPACING,
 )
 from ..geometry import NULL_OFFSET, Offset, Spacing
-from .scalar import Scalar
+from .scalar import Scalar, Unit
 from ._style_properties import (
     BorderProperty,
     BoxProperty,
@@ -115,10 +115,10 @@ class Styles:
     outline_bottom = BoxProperty()
     outline_left = BoxProperty()
 
-    width = ScalarProperty()
-    height = ScalarProperty()
-    min_width = ScalarProperty()
-    min_height = ScalarProperty()
+    width = ScalarProperty(percent_unit=Unit.WIDTH)
+    height = ScalarProperty(percent_unit=Unit.HEIGHT)
+    min_width = ScalarProperty(percent_unit=Unit.WIDTH)
+    min_height = ScalarProperty(percent_unit=Unit.HEIGHT)
 
     dock_group = DockGroupProperty()
     docks = DocksProperty()