1 files changed, 67 insertions, 0 deletions
diff --git a/src/library/place.rs b/src/library/place.rs
new file mode 100644
index 00000000..cee687fa
--- /dev/null
+++ b/src/library/place.rs
@@ -0,0 +1,67 @@
+//! Absolute placement of nodes.
+
+use super::prelude::*;
+use super::AlignNode;
+
+/// Place content at an absolute position.
+#[derive(Debug, Hash)]
+pub struct PlaceNode(pub PackedNode);
+
+#[class]
+impl PlaceNode {
+    fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Node> {
+        let aligns = args.find().unwrap_or(Spec::with_x(Some(Align::Left)));
+        let tx = args.named("dx")?.unwrap_or_default();
+        let ty = args.named("dy")?.unwrap_or_default();
+        let body: PackedNode = args.expect("body")?;
+        Ok(Node::block(Self(
+            body.moved(Point::new(tx, ty)).aligned(aligns),
+        )))
+    }
+}
+
+impl Layout for PlaceNode {
+    fn layout(
+        &self,
+        ctx: &mut LayoutContext,
+        regions: &Regions,
+        styles: StyleChain,
+    ) -> Vec<Constrained<Rc<Frame>>> {
+        let out_of_flow = self.out_of_flow();
+
+        // The pod is the base area of the region because for absolute
+        // placement we don't really care about the already used area (current).
+        let pod = {
+            let finite = regions.base.map(Length::is_finite);
+            let expand = finite & (regions.expand | out_of_flow);
+            Regions::one(regions.base, regions.base, expand)
+        };
+
+        let mut frames = self.0.layout(ctx, &pod, styles);
+        let Constrained { item: frame, cts } = &mut frames[0];
+
+        // If expansion is off, zero all sizes so that we don't take up any
+        // space in our parent. Otherwise, respect the expand settings.
+        let target = regions.expand.select(regions.current, Size::zero());
+        Rc::make_mut(frame).resize(target, Align::LEFT_TOP);
+
+        // Set base constraint because our pod size is base and exact
+        // constraints if we needed to expand or offset.
+        *cts = Constraints::new(regions.expand);
+        cts.base = regions.base.map(Some);
+        cts.exact = regions.current.filter(regions.expand | out_of_flow);
+
+        frames
+    }
+}
+
+impl PlaceNode {
+    /// Whether this node wants to be placed relative to its its parent's base
+    /// origin. instead of relative to the parent's current flow/cursor
+    /// position.
+    pub fn out_of_flow(&self) -> bool {
+        self.0
+            .downcast::<AlignNode>()
+            .map_or(false, |node| node.aligns.y.is_some())
+    }
+}