Rethink workspace structure

src/layout.rs

@@ -0,0 +1,62 @@
+use stretch::result;
+
+use crate::{Point, Rectangle, Vector};
+
+/// The computed bounds of a [`Node`] and its children.
+///
+/// This type is provided by the GUI runtime to [`Widget::on_event`] and
+/// [`Widget::draw`], describing the layout of the [`Node`] produced by
+/// [`Widget::node`].
+///
+/// [`Node`]: struct.Node.html
+/// [`Widget::on_event`]: widget/trait.Widget.html#method.on_event
+/// [`Widget::draw`]: widget/trait.Widget.html#tymethod.draw
+/// [`Widget::node`]: widget/trait.Widget.html#tymethod.node
+#[derive(Debug)]
+pub struct Layout<'a> {
+    layout: &'a result::Layout,
+    position: Point,
+}
+
+impl<'a> Layout<'a> {
+    pub(crate) fn new(layout: &'a result::Layout) -> Self {
+        Self::with_parent_position(layout, Point::new(0.0, 0.0))
+    }
+
+    fn with_parent_position(
+        layout: &'a result::Layout,
+        parent_position: Point,
+    ) -> Self {
+        let position =
+            parent_position + Vector::new(layout.location.x, layout.location.y);
+
+        Layout { layout, position }
+    }
+
+    /// Gets the bounds of the [`Layout`].
+    ///
+    /// The returned [`Rectangle`] describes the position and size of a
+    /// [`Node`].
+    ///
+    /// [`Layout`]: struct.Layout.html
+    /// [`Rectangle`]: struct.Rectangle.html
+    /// [`Node`]: struct.Node.html
+    pub fn bounds(&self) -> Rectangle {
+        Rectangle {
+            x: self.position.x,
+            y: self.position.y,
+            width: self.layout.size.width,
+            height: self.layout.size.height,
+        }
+    }
+
+    /// Returns an iterator over the [`Layout`] of the children of a [`Node`].
+    ///
+    /// [`Layout`]: struct.Layout.html
+    /// [`Node`]: struct.Node.html
+    pub fn children(&'a self) -> impl Iterator<Item = Layout<'a>> {
+        self.layout.children.iter().map(move |layout| {
+            Layout::with_parent_position(layout, self.position)
+        })
+    }
+}