feat: implement nested border-box layout and alignment

src/render/scroll.rs

@@ -76,11 +76,8 @@ pub fn project(vm: &mut Vm, table: &MountTable, root: &UiNode, frame: &mut Frame
         .mounts
         .iter()
         .map(|m| {
-            let padding = match nodes[m.block_id.as_str()].kind {
-                UiKind::Scroll { padding, .. } => padding,
-                _ => 0.0,
-            };
-            (m.x + m.width - padding, m.y + m.height - padding)
+            let inset = layout::insets(nodes[m.block_id.as_str()]);
+            (m.x + m.width - inset.right, m.y + m.height - inset.bottom)
         })
         .collect();
     for i in (0..frame.mounts.len()).rev() {
@@ -104,22 +101,20 @@ pub fn project(vm: &mut Vm, table: &MountTable, root: &UiNode, frame: &mut Frame
             .parent
             .and_then(|id| contexts.get(&id).copied())
             .unwrap_or_default();
-        let padding = match nodes[m.block_id.as_str()].kind {
-            UiKind::Scroll { padding, .. } => padding,
-            _ => 0.0,
-        };
+        let node = nodes[m.block_id.as_str()];
+        let padding = layout::insets(node);
         let axis = match nodes[m.block_id.as_str()].kind {
             UiKind::Scroll { axis, .. } => axis,
             _ => Axis::Both,
         };
         let limits = [
             if axis.horizontal() {
-                (extent[i].0 + padding - m.x - m.width).max(0.0)
+                (extent[i].0 + padding.right - m.x - m.width).max(0.0)
             } else {
                 0.0
             },
             if axis.vertical() {
-                (extent[i].1 + padding - m.y - m.height).max(0.0)
+                (extent[i].1 + padding.bottom - m.y - m.height).max(0.0)
             } else {
                 0.0
             },
@@ -128,6 +123,19 @@ pub fn project(vm: &mut Vm, table: &MountTable, root: &UiNode, frame: &mut Frame
         m.y -= dy;
         m.clip = clip;
         let mut child = (dx, dy, clip);
+        if node.clip_children {
+            let border = node.border;
+            let viewport = [
+                m.x + border.left.min(m.width),
+                m.y + border.top.min(m.height),
+                (m.width - border.horizontal()).max(0.0),
+                (m.height - border.vertical()).max(0.0),
+            ];
+            child.2 = Some(
+                clip.map(|clip| intersection(clip, viewport))
+                    .unwrap_or(viewport),
+            );
+        }
         if scrolling[i] {
             let weak = table
                 .active
@@ -149,13 +157,15 @@ pub fn project(vm: &mut Vm, table: &MountTable, root: &UiNode, frame: &mut Frame
                 dx + x,
                 dy + y,
                 Some(
-                    clip.map(|clip| intersection(clip, viewport))
+                    child
+                        .2
+                        .map(|clip| intersection(clip, viewport))
                         .unwrap_or(viewport),
                 ),
             );
         }
         contexts.insert(m.id, child);
-        if let Some(command) = layout::paint_native(
+        for command in layout::paint_commands(
             nodes[m.block_id.as_str()],
             m.x,
             m.y,