Set Rules Episode IX: The Rise of Testing

1 files changed, 63 insertions, 0 deletions

diff --git a/src/library/heading.rs b/src/library/heading.rs
new file mode 100644
index 00000000..c9777577
--- /dev/null
+++ b/src/library/heading.rs
@@ -0,0 +1,63 @@
+use super::prelude::*;
+use super::{FontFamily, TextNode};
+
+/// A section heading.
+#[derive(Debug, Hash)]
+pub struct HeadingNode {
+    /// The node that produces the heading's contents.
+    pub child: PackedNode,
+    /// The logical nesting depth of the section, starting from one. In the
+    /// default style, this controls the text size of the heading.
+    pub level: usize,
+}
+
+#[properties]
+impl HeadingNode {
+    /// The heading's font family.
+    pub const FAMILY: Smart<String> = Smart::Auto;
+    /// The fill color of heading in the text. Just the surrounding text color
+    /// if `auto`.
+    pub const FILL: Smart<Paint> = Smart::Auto;
+}
+
+impl Construct for HeadingNode {
+    fn construct(_: &mut EvalContext, args: &mut Args) -> TypResult<Node> {
+        Ok(Node::block(Self {
+            child: args.expect::<Node>("body")?.into_block(),
+            level: args.named("level")?.unwrap_or(1),
+        }))
+    }
+}
+
+impl Set for HeadingNode {
+    fn set(styles: &mut Styles, args: &mut Args) -> TypResult<()> {
+        styles.set_opt(Self::FAMILY, args.named("family")?);
+        styles.set_opt(Self::FILL, args.named("fill")?);
+        Ok(())
+    }
+}
+
+impl Layout for HeadingNode {
+    fn layout(
+        &self,
+        ctx: &mut LayoutContext,
+        regions: &Regions,
+    ) -> Vec<Constrained<Rc<Frame>>> {
+        let upscale = (1.6 - 0.1 * self.level as f64).max(0.75);
+        ctx.styles.set(TextNode::STRONG, true);
+        ctx.styles.set(TextNode::SIZE, Relative::new(upscale).into());
+
+        if let Smart::Custom(family) = ctx.styles.get_ref(Self::FAMILY) {
+            let list: Vec<_> = std::iter::once(FontFamily::named(family))
+                .chain(ctx.styles.get_ref(TextNode::FAMILY_LIST).iter().cloned())
+                .collect();
+            ctx.styles.set(TextNode::FAMILY_LIST, list);
+        }
+
+        if let Smart::Custom(fill) = ctx.styles.get(Self::FILL) {
+            ctx.styles.set(TextNode::FILL, fill);
+        }
+
+        self.child.layout(ctx, regions)
+    }
+}