feat: navigation

backend/uframe/measure.py

@@ -8,7 +8,7 @@ from uframe.ir import (
     Gauge, Sparkline, Status, Table,
     Form, Field, Password, Radio, Checkbox, FormButton,
     Let, Source, IfBlock, ForLoop, CacheControl, OnSubmit, StateDecl,
-    BigTitle, ImageNode,
+    BigTitle, ImageNode, HNav, VNav,
 )
 from uframe.fonts import FONT_HEIGHTS, get_text_width
 from uframe.imaging import get_image_height
@@ -246,6 +246,33 @@ def measure(node: IRNode, available_width: int) -> None:
         node.pref_height = 1
         node.min_height = 1
 
+    elif isinstance(node, HNav):
+        # Height: 3 for bar/tabs/pills (top border + items + bottom border), 2 for underline/breadcrumb
+        if node.nav_style in ("underline",):
+            node.pref_height = 2
+        elif node.nav_style in ("breadcrumb",):
+            node.pref_height = 1
+        else:
+            node.pref_height = 3
+        node.pref_width = available_width
+        node.min_width = 10
+        node.min_height = 1
+
+    elif isinstance(node, VNav):
+        count = sum(1 for it in node.items if it.kind in ("item", "heading"))
+        sep_count = sum(1 for it in node.items if it.kind == "separator")
+        h = count + sep_count
+        if node.nav_style == "boxed":
+            h += 2  # top + bottom border
+        node.pref_height = max(h, 1)
+        if node.nav_width > 0:
+            node.pref_width = node.nav_width
+        else:
+            max_label = max((len(it.label) for it in node.items if it.label), default=8)
+            node.pref_width = max_label + 6  # marker + padding
+        node.min_width = 8
+        node.min_height = 1
+
     elif isinstance(node, ImageNode):
         h = get_image_height(node.path, node.mode, node.img_width)
         if node.caption: