Draft custom layout engine based on druid

native/src/layout.rs

@@ -1,57 +1,50 @@
-use crate::Rectangle;
-
 mod limits;
+mod node;
+
+pub mod flex;
 
 pub use limits::Limits;
+pub use node::Node;
 
-/// 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, Clone)]
-pub struct Layout {
-    bounds: Rectangle,
-    children: Vec<Layout>,
+use crate::{Point, Rectangle, Vector};
+
+#[derive(Debug, Clone, Copy)]
+pub struct Layout<'a> {
+    position: Point,
+    node: &'a Node,
 }
 
-impl Layout {
-    pub fn new(bounds: Rectangle) -> Self {
-        Layout {
-            bounds,
-            children: Vec::new(),
+impl<'a> Layout<'a> {
+    pub(crate) fn new(node: &'a Node) -> Self {
+        Self::with_offset(Vector::new(0.0, 0.0), node)
+    }
+
+    pub(crate) fn with_offset(offset: Vector, node: &'a Node) -> Self {
+        let bounds = node.bounds();
+
+        Self {
+            position: Point::new(bounds.x, bounds.y) + offset,
+            node,
         }
     }
 
-    pub fn push(&mut self, mut child: Layout) {
-        child.bounds.x += self.bounds.x;
-        child.bounds.y += self.bounds.y;
-
-        self.children.push(child);
-    }
-
-    /// 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 {
-        self.bounds
+        let bounds = self.node.bounds();
+
+        Rectangle {
+            x: self.position.x,
+            y: self.position.y,
+            width: bounds.width,
+            height: bounds.height,
+        }
     }
 
-    /// Returns an iterator over the [`Layout`] of the children of a [`Node`].
-    ///
-    /// [`Layout`]: struct.Layout.html
-    /// [`Node`]: struct.Node.html
-    pub fn children(&self) -> impl Iterator<Item = &Layout> {
-        self.children.iter()
+    pub fn children(&'a self) -> impl Iterator<Item = Layout<'a>> {
+        self.node.children().iter().map(move |node| {
+            Layout::with_offset(
+                Vector::new(self.position.x, self.position.y),
+                node,
+            )
+        })
     }
 }