Introduce useful helpers in layout module

core/src/layout.rs

@@ -7,7 +7,7 @@ pub mod flex;
 pub use limits::Limits;
 pub use node::Node;
 
-use crate::{Point, Rectangle, Size, Vector};
+use crate::{Length, Padding, Point, Rectangle, Size, Vector};
 
 /// The bounds of a [`Node`] and its children, using absolute coordinates.
 #[derive(Debug, Clone, Copy)]
@@ -96,3 +96,95 @@ pub fn next_to_each_other(
         ],
     )
 }
+
+/// Computes the resulting [`Node`] that fits the [`Limits`] given
+/// some width and height requirements and no intrinsic size.
+pub fn atomic(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+
+    Node::new(limits.resolve(width, height, Size::ZERO))
+}
+
+/// Computes the resulting [`Node`] that fits the [`Limits`] given
+/// some width and height requirements and a closure that produces
+/// the intrinsic [`Size`] inside the given [`Limits`].
+pub fn sized(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    f: impl FnOnce(&Limits) -> Size,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+
+    let limits = limits.width(width).height(height);
+    let intrinsic_size = f(&limits);
+
+    Node::new(limits.resolve(width, height, intrinsic_size))
+}
+
+/// Computes the resulting [`Node`] that fits the [`Limits`] given
+/// some width and height requirements and a closure that produces
+/// the content [`Node`] inside the given [`Limits`].
+pub fn contained(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    f: impl FnOnce(&Limits) -> Node,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+
+    let limits = limits.width(width).height(height);
+    let content = f(&limits);
+
+    Node::with_children(
+        limits.resolve(width, height, content.size()),
+        vec![content],
+    )
+}
+
+/// Computes the [`Node`] that fits the [`Limits`] given some width, height, and
+/// [`Padding`] requirements and a closure that produces the content [`Node`]
+/// inside the given [`Limits`].
+pub fn padded(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    padding: impl Into<Padding>,
+    layout: impl FnOnce(&Limits) -> Node,
+) -> Node {
+    positioned(limits, width, height, padding, layout, |content, _| content)
+}
+
+/// Computes a [`padded`] [`Node`] with a positioning step.
+pub fn positioned(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    padding: impl Into<Padding>,
+    layout: impl FnOnce(&Limits) -> Node,
+    position: impl FnOnce(Node, Size) -> Node,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+    let padding = padding.into();
+
+    let limits = limits.width(width).height(height);
+    let content = layout(&limits.shrink(padding));
+    let padding = padding.fit(content.size(), limits.max());
+
+    let size = limits
+        .shrink(padding)
+        .resolve(width, height, content.size());
+
+    Node::with_children(
+        size.expand(padding),
+        vec![position(content.move_to((padding.left, padding.top)), size)],
+    )
+}