Add BoxableView and AnyBox

And remove `impl ViewWrapper for T: Deref<View>`
This means `Box<View>` doesn't implement `View` anymore.

src/view/mod.rs

@@ -65,6 +65,8 @@ use vec::Vec2;
 use views::IdView;
 
 /// A view that can be downcasted to its concrete type.
+///
+/// This trait is automatically implemented for any `T: View`.
 pub trait AnyView: View {
     /// Downcast self to a `Any`.
     fn as_any(&self) -> &Any;
@@ -105,7 +107,30 @@ impl<T: View> AnyView for T {
     }
 }
 
+/// Represents a type that can be made into a `Box<AnyView>`.
+pub trait BoxableView {
+    /// Returns a `Box<AnyView>`.
+    fn as_boxed_view(self) -> Box<AnyView>;
+}
+
+impl<T> BoxableView for T
+where
+    T: View,
+{
+    fn as_boxed_view(self) -> Box<AnyView> {
+        Box::new(self)
+    }
+}
+
+impl BoxableView for Box<AnyView> {
+    fn as_boxed_view(self) -> Box<AnyView> {
+        self
+    }
+}
+
 /// Main trait defining a view behaviour.
+///
+/// This is what you should implement to define a custom View.
 pub trait View: Any {
     /// Called when a key was pressed.
     ///

src/view/view_wrapper.rs

@@ -95,32 +95,6 @@ pub trait ViewWrapper: 'static {
     }
 }
 
-// Some types easily implement ViewWrapper.
-// This includes Box<T: View>
-use std::ops::{Deref, DerefMut};
-
-impl<U, T> ViewWrapper for T
-where
-    U: View + ?Sized,
-    T: Deref<Target = U> + DerefMut + 'static,
-{
-    type V = U;
-
-    fn with_view<F, R>(&self, f: F) -> Option<R>
-    where
-        F: FnOnce(&Self::V) -> R,
-    {
-        Some(f(self.deref()))
-    }
-
-    fn with_view_mut<F, R>(&mut self, f: F) -> Option<R>
-    where
-        F: FnOnce(&mut Self::V) -> R,
-    {
-        Some(f(self.deref_mut()))
-    }
-}
-
 // The main point of implementing ViewWrapper is to have View for free.
 impl<T: ViewWrapper> View for T {
     fn draw(&self, printer: &Printer) {

src/views/any_box.rs

@@ -0,0 +1,56 @@
+use std::ops::{Deref, DerefMut};
+use view::{AnyView, View, ViewWrapper};
+
+/// A boxed `AnyView`.
+pub struct AnyBox {
+    view: Box<AnyView>,
+}
+
+impl AnyBox {
+    /// Creates a new `AnyBox` around the given boxed view.
+    pub fn new(view: Box<AnyView>) -> Self {
+        AnyBox { view }
+    }
+
+    /// Box the given view
+    pub fn boxed<T: View>(view: T) -> Self {
+        AnyBox::new(Box::new(view))
+    }
+
+    /// Returns the inner boxed view.
+    pub fn unwrap(self) -> Box<AnyView> {
+        self.view
+    }
+}
+
+impl Deref for AnyBox {
+    type Target = AnyView;
+
+    fn deref(&self) -> &AnyView {
+        &*self.view
+    }
+}
+
+impl DerefMut for AnyBox {
+    fn deref_mut(&mut self) -> &mut AnyView {
+        &mut *self.view
+    }
+}
+
+impl ViewWrapper for AnyBox {
+    type V = AnyView;
+
+    fn with_view<F, R>(&self, f: F) -> Option<R>
+    where
+        F: FnOnce(&Self::V) -> R,
+    {
+        Some(f(&*self.view))
+    }
+
+    fn with_view_mut<F, R>(&mut self, f: F) -> Option<R>
+    where
+        F: FnOnce(&mut Self::V) -> R,
+    {
+        Some(f(&mut *self.view))
+    }
+}

src/views/dialog.rs

@@ -11,7 +11,7 @@ use theme::ColorStyle;
 use unicode_width::UnicodeWidthStr;
 use vec::{Vec2, Vec4};
 use view::{AnyView, Selector, View};
-use views::{Button, DummyView, SizedView, TextView};
+use views::{AnyBox, Button, DummyView, SizedView, TextView};
 
 /// Identifies currently focused element in [`Dialog`].
 ///
@@ -58,7 +58,7 @@ pub struct Dialog {
     title_position: HAlign,
 
     // The actual inner view.
-    content: SizedView<Box<AnyView>>,
+    content: SizedView<AnyBox>,
 
     // Optional list of buttons under the main view.
     // Include the top-left corner.
@@ -90,7 +90,7 @@ impl Dialog {
     /// Creates a new `Dialog` with the given content.
     pub fn around<V: View + 'static>(view: V) -> Self {
         Dialog {
-            content: SizedView::new(Box::new(view)),
+            content: SizedView::new(AnyBox::boxed(view)),
             buttons: Vec::new(),
             title: String::new(),
             title_position: HAlign::Center,
@@ -133,7 +133,7 @@ impl Dialog {
     ///
     /// Previous content will be dropped.
     pub fn set_content<V: View + 'static>(&mut self, view: V) {
-        self.content = SizedView::new(Box::new(view));
+        self.content = SizedView::new(AnyBox::boxed(view));
     }
 
     /// Convenient method to create a dialog with a simple text content.

src/views/mod.rs

@@ -35,6 +35,7 @@ macro_rules! impl_enabled {
     }
 }
 
+mod any_box;
 mod box_view;
 mod button;
 mod canvas;
@@ -61,6 +62,7 @@ mod text_area;
 mod text_view;
 mod tracked_view;
 
+pub use self::any_box::AnyBox;
 pub use self::box_view::BoxView;
 pub use self::button::Button;
 pub use self::canvas::Canvas;

src/views/stack_view.rs

@@ -8,7 +8,7 @@ use std::ops::Deref;
 use theme::ColorStyle;
 use vec::Vec2;
 use view::{AnyView, Offset, Position, Selector, View, ViewWrapper};
-use views::{Layer, ShadowView};
+use views::{AnyBox, Layer, ShadowView};
 
 /// Simple stack of views.
 /// Only the top-most view is active and can receive input.
@@ -152,7 +152,7 @@ impl<T: View> View for ChildWrapper<T> {
 }
 
 struct Child {
-    view: ChildWrapper<Box<AnyView>>,
+    view: ChildWrapper<AnyBox>,
     size: Vec2,
     placement: Placement,
 
@@ -182,7 +182,7 @@ impl StackView {
     where
         T: 'static + View,
     {
-        let boxed: Box<AnyView> = Box::new(view);
+        let boxed = AnyBox::boxed(view);
         self.layers.push(Child {
             view: ChildWrapper::Plain(Layer::new(boxed)),
             size: Vec2::zero(),
@@ -275,7 +275,7 @@ impl StackView {
     where
         T: 'static + View,
     {
-        let boxed: Box<AnyView> = Box::new(view);
+        let boxed = AnyBox::boxed(view);
         self.layers.push(Child {
             // Skip padding for absolute/parent-placed views
             view: ChildWrapper::Shadow(
@@ -302,7 +302,11 @@ impl StackView {
     /// Remove the top-most layer.
     pub fn pop_layer(&mut self) -> Option<Box<AnyView>> {
         self.bg_dirty.set(true);
-        self.layers.pop().map(|child| child.view.unwrap())
+        self.layers
+            .pop()
+            .map(|child| child.view)
+            .map(ChildWrapper::unwrap)
+            .map(AnyBox::unwrap)
     }
 
     /// Computes the offset of the current top view.