Use Frame for rendering instead of Buffer

src/frame.rs

@@ -0,0 +1,41 @@
+use crossterm::style::ContentStyle;
+
+use crate::buffer::Buffer;
+pub use crate::buffer::{Pos, Size};
+
+#[derive(Debug, Default)]
+pub struct Frame {
+    pub(crate) buffer: Buffer,
+    cursor: Option<Pos>,
+}
+
+impl Frame {
+    pub fn size(&self) -> Size {
+        self.buffer.size()
+    }
+
+    pub fn reset(&mut self) {
+        self.buffer.reset();
+        self.cursor = None;
+    }
+
+    pub fn cursor(&self) -> Option<Pos> {
+        self.cursor
+    }
+
+    pub fn set_cursor(&mut self, pos: Option<Pos>) {
+        self.cursor = pos;
+    }
+
+    pub fn show_cursor(&mut self, pos: Pos) {
+        self.set_cursor(Some(pos));
+    }
+
+    pub fn hide_cursor(&mut self) {
+        self.set_cursor(None);
+    }
+
+    pub fn write(&mut self, pos: Pos, content: &str, style: ContentStyle) {
+        self.buffer.write(pos, content, style);
+    }
+}