diff --git a/src/vec.rs b/src/vec.rs
index 632471c..5f8716e 100644
--- a/src/vec.rs
+++ b/src/vec.rs
@@ -242,7 +242,7 @@ impl Mul<usize> for XY<usize> {
 
 /// Four values representing each direction.
 #[derive(Clone, Copy)]
-pub struct Vec4 {
+pub struct Margins {
     /// Left margin
     pub left: usize,
     /// Right margin
@@ -253,10 +253,10 @@ pub struct Vec4 {
     pub bottom: usize,
 }
 
-impl Vec4 {
-    /// Creates a new Vec4.
+impl Margins {
+    /// Creates a new Margins.
     pub fn new(left: usize, right: usize, top: usize, bottom: usize) -> Self {
-        Vec4 {
+        Margins {
             left: left,
             right: right,
             top: top,
@@ -290,38 +290,38 @@ impl Vec4 {
     }
 }
 
-impl From<(usize, usize, usize, usize)> for Vec4 {
-    fn from((left, right, top, bottom): (usize, usize, usize, usize)) -> Vec4 {
-        Vec4::new(left, right, top, bottom)
+impl From<(usize, usize, usize, usize)> for Margins {
+    fn from((left, right, top, bottom): (usize, usize, usize, usize)) -> Margins {
+        Margins::new(left, right, top, bottom)
     }
 }
 
-impl From<(i32, i32, i32, i32)> for Vec4 {
-    fn from((left, right, top, bottom): (i32, i32, i32, i32)) -> Vec4 {
+impl From<(i32, i32, i32, i32)> for Margins {
+    fn from((left, right, top, bottom): (i32, i32, i32, i32)) -> Margins {
         (left as usize, right as usize, top as usize, bottom as usize).into()
     }
 }
 
-impl From<((i32, i32), (i32, i32))> for Vec4 {
-    fn from(((left, right), (top, bottom)): ((i32, i32), (i32, i32))) -> Vec4 {
+impl From<((i32, i32), (i32, i32))> for Margins {
+    fn from(((left, right), (top, bottom)): ((i32, i32), (i32, i32))) -> Margins {
         (left, right, top, bottom).into()
     }
 }
-impl From<((usize, usize), (usize, usize))> for Vec4 {
+impl From<((usize, usize), (usize, usize))> for Margins {
     fn from(
         ((left, right), (top, bottom)): ((usize, usize), (usize, usize))
-    ) -> Vec4 {
+    ) -> Margins {
         (left, right, top, bottom).into()
     }
 }
 
-impl<T: Into<Vec4>> Add<T> for Vec4 {
-    type Output = Vec4;
+impl<T: Into<Margins>> Add<T> for Margins {
+    type Output = Margins;
 
-    fn add(self, other: T) -> Vec4 {
+    fn add(self, other: T) -> Margins {
         let ov = other.into();
 
-        Vec4 {
+        Margins {
             left: self.left + ov.left,
             right: self.right + ov.right,
             top: self.top + ov.top,
@@ -330,13 +330,13 @@ impl<T: Into<Vec4>> Add<T> for Vec4 {
     }
 }
 
-impl<T: Into<Vec4>> Sub<T> for Vec4 {
-    type Output = Vec4;
+impl<T: Into<Margins>> Sub<T> for Margins {
+    type Output = Margins;
 
-    fn sub(self, other: T) -> Vec4 {
+    fn sub(self, other: T) -> Margins {
         let ov = other.into();
 
-        Vec4 {
+        Margins {
             left: self.left - ov.left,
             right: self.right - ov.right,
             top: self.top - ov.top,
@@ -345,11 +345,11 @@ impl<T: Into<Vec4>> Sub<T> for Vec4 {
     }
 }
 
-impl Div<usize> for Vec4 {
-    type Output = Vec4;
+impl Div<usize> for Margins {
+    type Output = Margins;
 
-    fn div(self, other: usize) -> Vec4 {
-        Vec4 {
+    fn div(self, other: usize) -> Margins {
+        Margins {
             left: self.left / other,
             right: self.right / other,
             top: self.top / other,
@@ -358,11 +358,11 @@ impl Div<usize> for Vec4 {
     }
 }
 
-impl Mul<usize> for Vec4 {
-    type Output = Vec4;
+impl Mul<usize> for Margins {
+    type Output = Margins;
 
-    fn mul(self, other: usize) -> Vec4 {
-        Vec4 {
+    fn mul(self, other: usize) -> Margins {
+        Margins {
             left: self.left * other,
             right: self.right * other,
             top: self.top * other,
diff --git a/src/view/view.rs b/src/view/view.rs
index 8d03c06..b6221db 100644
--- a/src/view/view.rs
+++ b/src/view/view.rs
@@ -9,24 +9,21 @@ use view::{AnyView, Selector};
 ///
 /// This is what you should implement to define a custom View.
 pub trait View: Any + AnyView {
-    /// Called when a key was pressed.
-    ///
-    /// Default implementation just ignores it.
-    fn on_event(&mut self, Event) -> EventResult {
-        EventResult::Ignored
-    }
 
-    /// Returns the minimum size the view requires with the given restrictions.
+    /// Draws the view with the given printer (includes bounds) and focus.
     ///
-    /// If the view is flexible (it has multiple size options), it can try
-    /// to return one that fits the given `constraint`.
-    /// It's also fine to ignore it and return a fixed value.
+    /// This is the only *required* method to implement.
+    fn draw(&self, printer: &Printer);
+
+    /// Called once the size for this view has been decided.
     ///
-    /// Default implementation always return `(1,1)`.
-    fn required_size(&mut self, constraint: Vec2) -> Vec2 {
-        let _ = constraint;
-        Vec2::new(1, 1)
-    }
+    /// It can be used to pre-compute the configuration of child views.
+    ///
+    /// View groups should propagate the information to their children.
+    ///
+    /// At this point, the given size is final and cannot be negociated.
+    /// It is guaranteed to be the size available for the call to `draw()`.
+    fn layout(&mut self, Vec2) {}
 
     /// Returns `true` if the view content changed since last layout phase.
     ///
@@ -43,13 +40,29 @@ pub trait View: Any + AnyView {
         true
     }
 
-    /// Called once the size for this view has been decided,
+    /// Returns the minimum size the view requires with the given restrictions.
     ///
-    /// View groups should propagate the information to their children.
-    fn layout(&mut self, Vec2) {}
+    /// This is the main way a view communicate its size to its parent.
+    ///
+    /// If the view is flexible (it has multiple size options), it can try
+    /// to return one that fits the given `constraint`.
+    /// It's also fine to ignore it and return a fixed value.
+    ///
+    /// Default implementation always return `(1,1)`.
+    fn required_size(&mut self, constraint: Vec2) -> Vec2 {
+        let _ = constraint;
+        Vec2::new(1, 1)
+    }
+
+    /// Called when an event is received (key press, mouse event, ...).
+    ///
+    /// You can return an `EventResult`, with an optional callback to be run.
+    ///
+    /// Default implementation just ignores it.
+    fn on_event(&mut self, Event) -> EventResult {
+        EventResult::Ignored
+    }
 
-    /// Draws the view with the given printer (includes bounds) and focus.
-    fn draw(&self, printer: &Printer);
 
     /// Runs a closure on the view identified by the given selector.
     ///
diff --git a/src/views/dialog.rs b/src/views/dialog.rs
index 076b3c6..063982b 100644
--- a/src/views/dialog.rs
+++ b/src/views/dialog.rs
@@ -9,7 +9,7 @@ use std::cell::Cell;
 use std::cmp::max;
 use theme::ColorStyle;
 use unicode_width::UnicodeWidthStr;
-use vec::{Vec2, Vec4};
+use vec::{Vec2, Margins};
 use view::{Selector, View};
 use views::{Button, DummyView, SizedView, TextView, ViewBox};
 
@@ -65,10 +65,10 @@ pub struct Dialog {
     buttons: Vec<ChildButton>,
 
     // Padding around the inner view.
-    padding: Vec4,
+    padding: Margins,
 
     // Borders around everything.
-    borders: Vec4,
+    borders: Margins,
 
     // The current element in focus
     focus: DialogFocus,
@@ -95,8 +95,8 @@ impl Dialog {
             title: String::new(),
             title_position: HAlign::Center,
             focus: DialogFocus::Content,
-            padding: Vec4::new(1, 1, 0, 0),
-            borders: Vec4::new(1, 1, 1, 1),
+            padding: Margins::new(1, 1, 0, 0),
+            borders: Margins::new(1, 1, 1, 1),
             align: Align::top_right(),
         }
     }
@@ -214,7 +214,7 @@ impl Dialog {
     }
 
     /// Sets the padding in the dialog (around content and buttons).
-    pub fn padding<T: Into<Vec4>>(mut self, padding: T) -> Self {
+    pub fn padding<T: Into<Margins>>(mut self, padding: T) -> Self {
         self.padding = padding.into();
 
         self