Add code example for `Constraint::Ratio`

src/layout.rs

@@ -86,12 +86,59 @@ impl Layout {
     /// # use tui::layout::{Rect, Constraint, Direction, Layout};
     ///
     /// # fn main() {
-    ///     let chunks = Layout::default()
-    ///         .direction(Direction::Vertical)
-    ///         .constraints([Constraint::Length(5), Constraint::Min(0)].as_ref())
-    ///         .split(Rect{x: 2, y: 2, width: 10, height: 10});
-    ///     assert_eq!(chunks, vec![Rect{x:2, y: 2, width: 10, height: 5},
-    ///                             Rect{x: 2, y: 7, width: 10, height: 5}])
+    ///       let chunks = Layout::default()
+    ///           .direction(Direction::Vertical)
+    ///           .constraints([Constraint::Length(5), Constraint::Min(0)].as_ref())
+    ///           .split(Rect {
+    ///               x: 2,
+    ///               y: 2,
+    ///               width: 10,
+    ///               height: 10,
+    ///           });
+    ///       assert_eq!(
+    ///           chunks,
+    ///           vec![
+    ///               Rect {
+    ///                   x: 2,
+    ///                   y: 2,
+    ///                   width: 10,
+    ///                   height: 5
+    ///               },
+    ///               Rect {
+    ///                   x: 2,
+    ///                   y: 7,
+    ///                   width: 10,
+    ///                   height: 5
+    ///               }
+    ///           ]
+    ///       );
+    ///
+    ///       let chunks = Layout::default()
+    ///           .direction(Direction::Horizontal)
+    ///           .constraints([Constraint::Ratio(1, 3), Constraint::Ratio(2, 3)].as_ref())
+    ///           .split(Rect {
+    ///               x: 0,
+    ///               y: 0,
+    ///               width: 9,
+    ///               height: 2,
+    ///           });
+    ///       assert_eq!(
+    ///           chunks,
+    ///           vec![
+    ///               Rect {
+    ///                   x: 0,
+    ///                   y: 0,
+    ///                   width: 3,
+    ///                   height: 2
+    ///               },
+    ///               Rect {
+    ///                   x: 3,
+    ///                   y: 0,
+    ///                   width: 6,
+    ///                   height: 2
+    ///               }
+    ///           ]
+    ///       );
     /// # }
     ///
     /// ```