Add Background widget

src/ui/widgets.rs

@@ -1,3 +1,4 @@
+pub mod background;
 pub mod list;
 pub mod text;
 

src/ui/widgets/background.rs

@@ -0,0 +1,36 @@
+use async_trait::async_trait;
+use crossterm::style::ContentStyle;
+use toss::frame::{Frame, Pos, Size};
+
+use super::Widget;
+
+pub struct Background {
+    inner: Box<dyn Widget + Send>,
+    style: ContentStyle,
+}
+
+impl Background {
+    pub fn new<W: 'static + Widget + Send>(inner: W, style: ContentStyle) -> Self {
+        Self {
+            inner: Box::new(inner),
+            style,
+        }
+    }
+}
+
+#[async_trait]
+impl Widget for Background {
+    fn size(&self, frame: &mut Frame, max_width: Option<u16>, max_height: Option<u16>) -> Size {
+        self.inner.size(frame, max_width, max_height)
+    }
+
+    async fn render(self: Box<Self>, frame: &mut Frame, pos: Pos, size: Size) {
+        for dy in 0..size.height {
+            for dx in 0..size.width {
+                frame.write(pos + Pos::new(dx.into(), dy.into()), (" ", self.style));
+            }
+        }
+
+        self.inner.render(frame, pos, size).await;
+    }
+}