From 44ebefbec23114d6ed7a96e7e3cb9078441aff31 Mon Sep 17 00:00:00 2001
From: Laurenz <laurmaedje@gmail.com>
Date: Sat, 29 Jan 2022 22:32:01 +0100
Subject: [PATCH] Add `hide` class

---
 src/library/hidden.rs     |  32 ++++++++++++++++++++++++++++++++
 src/library/mod.rs        |   3 +++
 tests/ref/layout/hide.png | Bin 0 -> 936 bytes
 tests/typ/layout/hide.typ |   5 +++++
 4 files changed, 40 insertions(+)
 create mode 100644 src/library/hidden.rs
 create mode 100644 tests/ref/layout/hide.png
 create mode 100644 tests/typ/layout/hide.typ

diff --git a/src/library/hidden.rs b/src/library/hidden.rs
new file mode 100644
index 00000000..7287bf3d
--- /dev/null
+++ b/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
+    }
+}
diff --git a/src/library/mod.rs b/src/library/mod.rs
index 51d57c3e..81c8fcdc 100644
--- a/src/library/mod.rs
+++ b/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");
diff --git a/tests/ref/layout/hide.png b/tests/ref/layout/hide.png
new file mode 100644
index 0000000000000000000000000000000000000000..8a60cf904d0a17efb2e118edce3d4274fb3c6242
GIT binary patch
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diff --git a/tests/typ/layout/hide.typ b/tests/typ/layout/hide.typ
new file mode 100644
index 00000000..a979b24f
--- /dev/null
+++ b/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]