From bd3ea469e901a23f21d9fb35617c91e66e15bccb Mon Sep 17 00:00:00 2001
From: Alexandre Bury <alexandre.bury@gmail.com>
Date: Fri, 16 Mar 2018 18:07:01 -0700
Subject: [PATCH] Add View::important_area

In preparation for ScrollView
---
 src/view/view.rs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/view/view.rs b/src/view/view.rs
index b6221db..2f99192 100644
--- a/src/view/view.rs
+++ b/src/view/view.rs
@@ -1,6 +1,7 @@
 use Printer;
 use direction::Direction;
 use event::{Event, EventResult};
+use rect::Rect;
 use std::any::Any;
 use vec::Vec2;
 use view::{AnyView, Selector};
@@ -9,7 +10,6 @@ use view::{AnyView, Selector};
 ///
 /// This is what you should implement to define a custom View.
 pub trait View: Any + AnyView {
-
     /// Draws the view with the given printer (includes bounds) and focus.
     ///
     /// This is the only *required* method to implement.
@@ -63,7 +63,6 @@ pub trait View: Any + AnyView {
         EventResult::Ignored
     }
 
-
     /// Runs a closure on the view identified by the given selector.
     ///
     /// See [`Finder::call_on`] for a nicer interface, implemented for all
@@ -97,4 +96,16 @@ pub trait View: Any + AnyView {
         let _ = source;
         false
     }
+
+    /// What part of the view is important and should be visible?
+    ///
+    /// When only part of this view can be visible, this helps
+    /// determine which part.
+    ///
+    /// It is given the view size (same size given to `layout`).
+    ///
+    /// Default implementation return the entire view.
+    fn important_area(&self, view_size: Vec2) -> Rect {
+        Rect::from_corners((0, 0), view_size)
+    }
 }