box model py

src/textual/_box_model.py

@@ -0,0 +1,76 @@
+from __future__ import annotations
+
+
+from typing import Callable, TYPE_CHECKING
+
+from .geometry import Size, Spacing
+from .css.styles import StylesBase
+
+
+def get_box_model(
+    styles: StylesBase,
+    container_size: Size,
+    parent_size: Size,
+    get_auto_width: Callable[[Size, Size], int],
+    get_auto_height: Callable[[Size, Size], int],
+) -> tuple[Size, Spacing]:
+    """Resolve the box model for this Styles.
+
+    Args:
+        container_size (Size): The size of the widget container.
+        parent_size (Size): The size widget's parent.
+
+    Returns:
+        tuple[Size, Spacing]: A tuple with the size of the content area and margin.
+    """
+
+    has_rule = styles.has_rule
+    width, height = container_size
+
+    extra = Size(0, 0)
+    if styles.box_sizing == "content-box":
+        if has_rule("padding"):
+            extra += styles.padding.totals
+        extra += styles.border.spacing.totals
+
+    else:  # border-box
+        extra -= styles.border.spacing.totals
+
+    if has_rule("width"):
+        if styles.width.is_auto:
+            # extra_width = styles.padding.width + styles.border.spacing.width
+            width = get_auto_width(container_size, parent_size)
+        else:
+            width = styles.width.resolve_dimension(container_size, parent_size)
+    else:
+        width = max(0, width - styles.margin.width)
+
+    if styles.min_width:
+        min_width = styles.min_width.resolve_dimension(container_size, parent_size)
+        width = max(width, min_width)
+
+    if styles.max_width:
+        max_width = styles.max_width.resolve_dimension(container_size, parent_size)
+        width = min(width, max_width)
+
+    if has_rule("height"):
+        if styles.height.is_auto:
+            extra_height = styles.padding.height + styles.border.spacing.height
+            height = get_auto_height(container_size, parent_size) + extra_height
+        else:
+            height = styles.height.resolve_dimension(container_size, parent_size)
+    else:
+        height = max(0, height - styles.margin.height)
+
+    if styles.min_height:
+        min_height = styles.min_height.resolve_dimension(container_size, parent_size)
+        height = max(height, min_height)
+
+    if styles.max_height:
+        max_height = styles.max_height.resolve_dimension(container_size, parent_size)
+        height = min(width, max_height)
+
+    size = Size(width, height) + extra
+    margin = styles.margin if has_rule("margin") else Spacing(0, 0, 0, 0)
+
+    return size, margin