Add Widget and AsyncWidget traits

Cargo.toml

@@ -4,6 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+async-trait = "0.1.64"
 crossterm = "0.26.0"
 unicode-linebreak = "0.1.4"
 unicode-segmentation = "1.10.1"

src/lib.rs

@@ -13,6 +13,7 @@ mod buffer;
 mod frame;
 mod styled;
 mod terminal;
+mod widget;
 mod widthdb;
 mod wrap;
 
@@ -20,4 +21,5 @@ pub use buffer::{Pos, Size};
 pub use frame::*;
 pub use styled::*;
 pub use terminal::*;
+pub use widget::*;
 pub use widthdb::*;

src/widget.rs

@@ -0,0 +1,28 @@
+use async_trait::async_trait;
+
+use crate::{Frame, Size};
+
+// TODO Feature-gate these traits
+
+pub trait Widget<E> {
+    fn size(
+        &self,
+        frame: &mut Frame,
+        max_width: Option<u16>,
+        max_height: Option<u16>,
+    ) -> Result<Size, E>;
+
+    fn draw(self, frame: &mut Frame) -> Result<(), E>;
+}
+
+#[async_trait]
+pub trait AsyncWidget<E> {
+    async fn size(
+        &self,
+        frame: &mut Frame,
+        max_width: Option<u16>,
+        max_height: Option<u16>,
+    ) -> Result<Size, E>;
+
+    async fn draw(self, frame: &mut Frame) -> Result<(), E>;
+}