1 files changed, 166 insertions, 0 deletions
diff --git a/src/library/elements/shape.rs b/src/library/elements/shape.rs
new file mode 100644
index 00000000..8b967412
--- /dev/null
+++ b/src/library/elements/shape.rs
@@ -0,0 +1,166 @@
+use std::f64::consts::SQRT_2;
+
+use crate::library::prelude::*;
+use crate::library::text::TextNode;
+
+/// Place a node into a sizable and fillable shape.
+#[derive(Debug, Hash)]
+pub struct ShapeNode<const S: ShapeKind>(pub Option<LayoutNode>);
+
+/// Place a node into a square.
+pub type SquareNode = ShapeNode<SQUARE>;
+
+/// Place a node into a rectangle.
+pub type RectNode = ShapeNode<RECT>;
+
+/// Place a node into a circle.
+pub type CircleNode = ShapeNode<CIRCLE>;
+
+/// Place a node into an ellipse.
+pub type EllipseNode = ShapeNode<ELLIPSE>;
+
+#[class]
+impl<const S: ShapeKind> ShapeNode<S> {
+    /// How to fill the shape.
+    pub const FILL: Option<Paint> = None;
+    /// How the stroke the shape.
+    pub const STROKE: Smart<Option<Paint>> = Smart::Auto;
+    /// The stroke's thickness.
+    pub const THICKNESS: Length = Length::pt(1.0);
+    /// How much to pad the shape's content.
+    pub const PADDING: Linear = Linear::zero();
+
+    fn construct(_: &mut Context, args: &mut Args) -> TypResult<Template> {
+        let size = match S {
+            SQUARE => args.named::<Length>("size")?.map(Linear::from),
+            CIRCLE => args.named::<Length>("radius")?.map(|r| 2.0 * Linear::from(r)),
+            _ => None,
+        };
+
+        let width = match size {
+            None => args.named("width")?,
+            size => size,
+        };
+
+        let height = match size {
+            None => args.named("height")?,
+            size => size,
+        };
+
+        Ok(Template::inline(
+            Self(args.find()?).pack().sized(Spec::new(width, height)),
+        ))
+    }
+}
+
+impl<const S: ShapeKind> Layout for ShapeNode<S> {
+    fn layout(
+        &self,
+        ctx: &mut Context,
+        regions: &Regions,
+        styles: StyleChain,
+    ) -> TypResult<Vec<Arc<Frame>>> {
+        let mut frames;
+        if let Some(child) = &self.0 {
+            let mut padding = styles.get(Self::PADDING);
+            if is_round(S) {
+                padding.rel += Relative::new(0.5 - SQRT_2 / 4.0);
+            }
+
+            // Pad the child.
+            let child = child.clone().padded(Sides::splat(padding));
+
+            let mut pod = Regions::one(regions.first, regions.base, regions.expand);
+            frames = child.layout(ctx, &pod, styles)?;
+
+            // Relayout with full expansion into square region to make sure
+            // the result is really a square or circle.
+            if is_quadratic(S) {
+                let length = if regions.expand.x || regions.expand.y {
+                    let target = regions.expand.select(regions.first, Size::zero());
+                    target.x.max(target.y)
+                } else {
+                    let size = frames[0].size;
+                    let desired = size.x.max(size.y);
+                    desired.min(regions.first.x).min(regions.first.y)
+                };
+
+                pod.first = Size::splat(length);
+                pod.expand = Spec::splat(true);
+                frames = child.layout(ctx, &pod, styles)?;
+            }
+        } else {
+            // The default size that a shape takes on if it has no child and
+            // enough space.
+            let mut size =
+                Size::new(Length::pt(45.0), Length::pt(30.0)).min(regions.first);
+
+            if is_quadratic(S) {
+                let length = if regions.expand.x || regions.expand.y {
+                    let target = regions.expand.select(regions.first, Size::zero());
+                    target.x.max(target.y)
+                } else {
+                    size.x.min(size.y)
+                };
+                size = Size::splat(length);
+            } else {
+                size = regions.expand.select(regions.first, size);
+            }
+
+            frames = vec![Arc::new(Frame::new(size))];
+        }
+
+        let frame = Arc::make_mut(&mut frames[0]);
+
+        // Add fill and/or stroke.
+        let fill = styles.get(Self::FILL);
+        let thickness = styles.get(Self::THICKNESS);
+        let stroke = styles
+            .get(Self::STROKE)
+            .unwrap_or(fill.is_none().then(|| Color::BLACK.into()))
+            .map(|paint| Stroke { paint, thickness });
+
+        if fill.is_some() || stroke.is_some() {
+            let geometry = if is_round(S) {
+                Geometry::Ellipse(frame.size)
+            } else {
+                Geometry::Rect(frame.size)
+            };
+
+            let shape = Shape { geometry, fill, stroke };
+            frame.prepend(Point::zero(), Element::Shape(shape));
+        }
+
+        // Apply link if it exists.
+        if let Some(url) = styles.get_ref(TextNode::LINK) {
+            frame.link(url);
+        }
+
+        Ok(frames)
+    }
+}
+
+/// A category of shape.
+pub type ShapeKind = usize;
+
+/// A rectangle with equal side lengths.
+const SQUARE: ShapeKind = 0;
+
+/// A quadrilateral with four right angles.
+const RECT: ShapeKind = 1;
+
+/// An ellipse with coinciding foci.
+const CIRCLE: ShapeKind = 2;
+
+/// A curve around two focal points.
+const ELLIPSE: ShapeKind = 3;
+
+/// Whether a shape kind is curvy.
+fn is_round(kind: ShapeKind) -> bool {
+    matches!(kind, CIRCLE | ELLIPSE)
+}
+
+/// Whether a shape kind has equal side length.
+fn is_quadratic(kind: ShapeKind) -> bool {
+    matches!(kind, SQUARE | CIRCLE)
+}