feat: added a twist

backend/uframe/layout.py

@@ -0,0 +1,134 @@
+"""Top-down layout pass — assign (x, y, w, h) positions to every node."""
+
+from __future__ import annotations
+
+from uframe.ir import (
+    IRNode, Page, Box, Row, Col, Spacer, Pad, Rect,
+    Heading, Text, Label, Divider, Link, ListNode, ListItem,
+    Gauge, Sparkline, Status,
+)
+
+
+def layout(node: IRNode, x: int, y: int, w: int, h: int) -> int:
+    """Assign positions to a node and its children.
+
+    Args:
+        node: the IR node to lay out
+        x, y: top-left position in the grid
+        w: available width
+        h: available height (advisory, may grow)
+
+    Returns:
+        The actual height consumed by this node.
+    """
+    node.rect = Rect(x=x, y=y, w=w, h=0)
+
+    if isinstance(node, Page):
+        cursor_y = y
+        for child in node.children:
+            child_h = layout(child, x, cursor_y, w, h - (cursor_y - y))
+            cursor_y += child_h
+        node.rect.h = cursor_y - y
+        return node.rect.h
+
+    elif isinstance(node, Box):
+        # Border takes 1 char on each side
+        inner_x = x + 1
+        inner_y = y + 1
+        inner_w = w - 2
+        cursor_y = inner_y
+        for child in node.children:
+            child_h = layout(child, inner_x, cursor_y, inner_w,
+                             h - 2 - (cursor_y - inner_y))
+            cursor_y += child_h
+        inner_h = cursor_y - inner_y
+        node.rect.h = inner_h + 2  # +2 for top/bottom border
+        return node.rect.h
+
+    elif isinstance(node, Row):
+        n = len(node.children)
+        if n == 0:
+            return 0
+
+        gap_total = node.gap * (n - 1)
+        usable = w - gap_total
+
+        # Distribute width
+        widths: list[int] = []
+        fixed_total = 0
+        flex_count = 0
+        for child in node.children:
+            if isinstance(child, Col) and child.col_width is not None:
+                widths.append(child.col_width)
+                fixed_total += child.col_width
+            else:
+                widths.append(0)
+                flex_count += 1
+
+        flex_each = max(1, (usable - fixed_total) // flex_count) if flex_count > 0 else 0
+        remainder = (usable - fixed_total) - (flex_each * flex_count) if flex_count > 0 else 0
+
+        for i, child in enumerate(node.children):
+            if widths[i] == 0:
+                widths[i] = flex_each
+                if remainder > 0:
+                    widths[i] += 1
+                    remainder -= 1
+
+        # Lay out each child at its column position
+        max_h = 0
+        col_x = x
+        for i, child in enumerate(node.children):
+            child_h = layout(child, col_x, y, widths[i], h)
+            max_h = max(max_h, child_h)
+            col_x += widths[i] + node.gap
+
+        node.rect.h = max_h
+        return max_h
+
+    elif isinstance(node, Col):
+        cursor_y = y
+        col_w = node.col_width if node.col_width is not None else w
+        col_w = min(col_w, w)
+        for child in node.children:
+            child_h = layout(child, x, cursor_y, col_w, h - (cursor_y - y))
+            cursor_y += child_h
+        node.rect.w = col_w
+        node.rect.h = cursor_y - y
+        return node.rect.h
+
+    elif isinstance(node, Spacer):
+        node.rect.h = node.lines
+        return node.lines
+
+    elif isinstance(node, Pad):
+        cursor_y = y + node.top
+        inner_w = w - node.left - node.right
+        for child in node.children:
+            child_h = layout(child, x + node.left, cursor_y, inner_w,
+                             h - node.top - node.bottom - (cursor_y - y - node.top))
+            cursor_y += child_h
+        node.rect.h = (cursor_y - y) + node.bottom
+        return node.rect.h
+
+    elif isinstance(node, (Heading, Text, Label, Divider, Link, ListItem,
+                           Gauge, Sparkline, Status)):
+        node.rect.h = node.pref_height
+        return node.pref_height
+
+    elif isinstance(node, ListNode):
+        cursor_y = y
+        for child in node.children:
+            child_h = layout(child, x + 2, cursor_y, w - 2, h - (cursor_y - y))
+            cursor_y += child_h
+        node.rect.h = cursor_y - y
+        return node.rect.h
+
+    else:
+        # Generic vertical stacking
+        cursor_y = y
+        for child in node.children:
+            child_h = layout(child, x, cursor_y, w, h - (cursor_y - y))
+            cursor_y += child_h
+        node.rect.h = cursor_y - y
+        return node.rect.h