Add hide class

src/library/hidden.rs

@@ -0,0 +1,32 @@
+//! Hiding of nodes without affecting layout.
+
+use super::prelude::*;
+
+/// A node that hides its child without affecting layout.
+#[derive(Debug, Hash)]
+pub struct HideNode(pub PackedNode);
+
+#[class]
+impl HideNode {
+    fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Node> {
+        Ok(Node::inline(Self(args.expect("body")?)))
+    }
+}
+
+impl Layout for HideNode {
+    fn layout(
+        &self,
+        ctx: &mut LayoutContext,
+        regions: &Regions,
+        styles: StyleChain,
+    ) -> Vec<Constrained<Rc<Frame>>> {
+        let mut frames = self.0.layout(ctx, regions, styles);
+
+        // Clear the frames.
+        for Constrained { item: frame, .. } in &mut frames {
+            *frame = Rc::new(Frame { elements: vec![], ..**frame });
+        }
+
+        frames
+    }
+}

src/library/mod.rs

@@ -10,6 +10,7 @@ pub mod deco;
 pub mod flow;
 pub mod grid;
 pub mod heading;
+pub mod hidden;
 pub mod image;
 pub mod link;
 pub mod list;
@@ -33,6 +34,7 @@ pub use deco::*;
 pub use flow::*;
 pub use grid::*;
 pub use heading::*;
+pub use hidden::*;
 pub use link::*;
 pub use list::*;
 pub use pad::*;
@@ -116,6 +118,7 @@ pub fn new() -> Scope {
     std.def_class::<TransformNode<Move>>("move");
     std.def_class::<TransformNode<Scale>>("scale");
     std.def_class::<TransformNode<Rotate>>("rotate");
+    std.def_class::<HideNode>("hide");
     std.def_class::<StackNode>("stack");
     std.def_class::<GridNode>("grid");
     std.def_class::<ColumnsNode>("columns");

tests/typ/layout/hide.typ

@@ -0,0 +1,5 @@
+// Test the `hide` function.
+
+---
+AB #h(1fr) CD \
+#hide[A]B #h(1fr) C#hide[D]