Add Cursor widget

src/widgets/cursor.rs

@@ -0,0 +1,67 @@
+use async_trait::async_trait;
+
+use crate::{AsyncWidget, Frame, Pos, Size, Widget};
+
+pub struct Cursor<I> {
+    inner: I,
+    at: Pos,
+}
+
+impl<I> Cursor<I> {
+    pub fn new(inner: I) -> Self {
+        Self {
+            inner,
+            at: Pos::ZERO,
+        }
+    }
+
+    pub fn at(mut self, pos: Pos) -> Self {
+        self.at = pos;
+        self
+    }
+
+    pub fn at_xy(self, x: i32, y: i32) -> Self {
+        self.at(Pos::new(x, y))
+    }
+}
+
+impl<E, I> Widget<E> for Cursor<I>
+where
+    I: Widget<E>,
+{
+    fn size(
+        &self,
+        frame: &mut Frame,
+        max_width: Option<u16>,
+        max_height: Option<u16>,
+    ) -> Result<Size, E> {
+        self.inner.size(frame, max_width, max_height)
+    }
+
+    fn draw(self, frame: &mut Frame) -> Result<(), E> {
+        self.inner.draw(frame)?;
+        frame.show_cursor(self.at);
+        Ok(())
+    }
+}
+
+#[async_trait]
+impl<E, I> AsyncWidget<E> for Cursor<I>
+where
+    I: AsyncWidget<E> + Send + Sync,
+{
+    async fn size(
+        &self,
+        frame: &mut Frame,
+        max_width: Option<u16>,
+        max_height: Option<u16>,
+    ) -> Result<Size, E> {
+        self.inner.size(frame, max_width, max_height).await
+    }
+
+    async fn draw(self, frame: &mut Frame) -> Result<(), E> {
+        self.inner.draw(frame).await?;
+        frame.show_cursor(self.at);
+        Ok(())
+    }
+}