Write docs for iced and iced_native

native/src/renderer.rs

@@ -32,9 +32,21 @@ pub use windowed::{Target, Windowed};
 
 use crate::{layout, Element};
 
+/// A component that can take the state of a user interface and produce an
+/// output for its users.
 pub trait Renderer: Sized {
+    /// The type of output of the [`Renderer`].
+    ///
+    /// If you are implementing a graphical renderer, your output will most
+    /// likely be a tree of visual primitives.
+    ///
+    /// [`Renderer`]: trait.Renderer.html
     type Output;
 
+    /// Lays out the elements of a user interface.
+    ///
+    /// You should override this if you need to perform any operations before or
+    /// after layouting. For instance, trimming the measurements cache.
     fn layout<'a, Message>(
         &mut self,
         element: &Element<'a, Message, Self>,