1 files changed, 76 insertions, 0 deletions
diff --git a/src/library/align.rs b/src/library/align.rs
new file mode 100644
index 00000000..8265c0f4
--- /dev/null
+++ b/src/library/align.rs
@@ -0,0 +1,76 @@
+use super::*;
+
+/// `align`: Align content along the layouting axes.
+///
+/// # Positional arguments
+/// - At most two of `left`, `right`, `top`, `bottom`, `center`.
+///
+/// # Keyword arguments
+/// - `horizontal`: Any of `left`, `right` or `center`.
+/// - `vertical`: Any of `top`, `bottom` or `center`.
+///
+/// There may not be two alignment specifications for the same axis.
+pub fn align(call: FuncCall, state: &ParseState) -> Pass<SyntaxNode> {
+    let mut f = Feedback::new();
+    let mut args = call.header.args;
+    let node = AlignNode {
+        body: parse_body_maybe(call.body, state, &mut f),
+        aligns: args.pos.all::<Spanned<SpecAlign>>().collect(),
+        h: args.key.get::<Spanned<SpecAlign>>("horizontal", &mut f),
+        v: args.key.get::<Spanned<SpecAlign>>("vertical", &mut f),
+    };
+    drain_args(args, &mut f);
+    Pass::node(node, f)
+}
+
+#[derive(Debug, Clone, PartialEq)]
+struct AlignNode {
+    body: Option<SyntaxTree>,
+    aligns: SpanVec<SpecAlign>,
+    h: Option<Spanned<SpecAlign>>,
+    v: Option<Spanned<SpecAlign>>,
+}
+
+#[async_trait(?Send)]
+impl Layout for AlignNode {
+    async fn layout<'a>(&'a self, mut ctx: LayoutContext<'_>) -> Pass<Commands<'a>> {
+        let mut f = Feedback::new();
+
+        ctx.base = ctx.spaces[0].size;
+
+        let axes = ctx.axes;
+        let all = self.aligns.iter()
+            .map(|align| {
+                let spec = align.v.axis().unwrap_or(axes.primary.axis());
+                (spec, align)
+            })
+            .chain(self.h.iter().map(|align| (Horizontal, align)))
+            .chain(self.v.iter().map(|align| (Vertical, align)));
+
+        let mut had = [false; 2];
+        for (axis, align) in all {
+            if align.v.axis().map(|a| a != axis).unwrap_or(false) {
+                error!(
+                    @f, align.span,
+                    "invalid alignment {} for {} axis", align.v, axis,
+                );
+            } else if had[axis as usize] {
+                error!(@f, align.span, "duplicate alignment for {} axis", axis);
+            } else {
+                had[axis as usize] = true;
+                let gen_axis = axis.to_generic(ctx.axes);
+                let gen_align = align.v.to_generic(ctx.axes);
+                *ctx.align.get_mut(gen_axis) = gen_align;
+            }
+        }
+
+        Pass::new(match &self.body {
+            Some(body) => {
+                let layouted = layout(body, ctx).await;
+                f.extend(layouted.feedback);
+                vec![AddMultiple(layouted.output)]
+            }
+            None => vec![SetAlignment(ctx.align)],
+        }, f)
+    }
+}