Implement `Empty` widget

It can be useful if you want to fill some space with nothing.

8 files changed, 191 insertions, 4 deletions

diff --git a/examples/tour.rs b/examples/tour.rs
index da05b396..fcace9c3 100644
--- a/examples/tour.rs
+++ b/examples/tour.rs
@@ -1,6 +1,6 @@
 use iced::{
     button, scrollable, slider, text_input, Button, Checkbox, Color, Column,
-    Container, Element, HorizontalAlignment, Image, Length, Radio, Row,
+    Container, Element, Empty, HorizontalAlignment, Image, Length, Radio, Row,
     Sandbox, Scrollable, Settings, Slider, Text, TextInput,
 };
 
@@ -67,7 +67,7 @@ impl Sandbox for Tour {
             );
         }
 
-        controls = controls.push(Column::new());
+        controls = controls.push(Empty::new().width(Length::Fill));
 
         if steps.can_continue() {
             controls = controls.push(
diff --git a/native/src/widget.rs b/native/src/widget.rs
index 26889280..b73f229e 100644
--- a/native/src/widget.rs
+++ b/native/src/widget.rs
@@ -24,6 +24,7 @@ pub mod button;
 pub mod checkbox;
 pub mod column;
 pub mod container;
+pub mod empty;
 pub mod image;
 pub mod radio;
 pub mod row;
@@ -42,6 +43,8 @@ pub use column::Column;
 #[doc(no_inline)]
 pub use container::Container;
 #[doc(no_inline)]
+pub use empty::Empty;
+#[doc(no_inline)]
 pub use image::Image;
 #[doc(no_inline)]
 pub use radio::Radio;
diff --git a/native/src/widget/empty.rs b/native/src/widget/empty.rs
new file mode 100644
index 00000000..f670048f
--- /dev/null
+++ b/native/src/widget/empty.rs
@@ -0,0 +1,103 @@
+//! Distribute content vertically.
+use std::hash::Hash;
+
+use crate::{
+    layout, Element, Hasher, Layout, Length, Point, Rectangle, Size, Widget,
+};
+
+/// An amount of empty space.
+///
+/// It can be useful if you want to fill some space with nothing.
+///
+/// [`Empty`]: struct.Empty.html
+#[derive(Debug)]
+pub struct Empty {
+    width: Length,
+    height: Length,
+}
+
+impl Empty {
+    /// Creates an amount of [`Empty`] space.
+    ///
+    /// [`Empty`]: struct.Empty.html
+    pub fn new() -> Self {
+        Empty {
+            width: Length::Shrink,
+            height: Length::Shrink,
+        }
+    }
+
+    /// Sets the width of the [`Empty`] space.
+    ///
+    /// [`Empty`]: struct..html
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Empty`] space.
+    ///
+    /// [`Empty`]: struct.Column.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+}
+
+impl<'a, Message, Renderer> Widget<Message, Renderer> for Empty
+where
+    Renderer: self::Renderer,
+{
+    fn width(&self) -> Length {
+        self.width
+    }
+
+    fn height(&self) -> Length {
+        self.height
+    }
+
+    fn layout(
+        &self,
+        _renderer: &Renderer,
+        limits: &layout::Limits,
+    ) -> layout::Node {
+        let limits = limits.width(self.width).height(self.height);
+
+        layout::Node::new(limits.resolve(Size::ZERO))
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        layout: Layout<'_>,
+        _cursor_position: Point,
+    ) -> Renderer::Output {
+        renderer.draw(layout.bounds())
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        std::any::TypeId::of::<Empty>().hash(state);
+        self.width.hash(state);
+        self.height.hash(state);
+    }
+}
+
+/// The renderer of an amount of [`Empty`] space.
+///
+/// [`Empty`]: struct.Empty.html
+pub trait Renderer: crate::Renderer {
+    /// Draws an amount of [`Empty`] space.
+    ///
+    /// You should most likely return an empty primitive here.
+    fn draw(&mut self, bounds: Rectangle) -> Self::Output;
+}
+
+impl<'a, Message, Renderer> From<Empty> for Element<'a, Message, Renderer>
+where
+    Renderer: self::Renderer,
+    Message: 'static,
+{
+    fn from(empty: Empty) -> Element<'a, Message, Renderer> {
+        Element::new(empty)
+    }
+}
diff --git a/src/native.rs b/src/native.rs
index f06f1c99..8a04b7c3 100644
--- a/src/native.rs
+++ b/src/native.rs
@@ -1,6 +1,6 @@
 pub use iced_winit::{
-    Align, Background, Color, Command, Font, HorizontalAlignment, Length,
-    Subscription, VerticalAlignment,
+    Align, Background, Color, Command, Empty, Font, HorizontalAlignment,
+    Length, Subscription, VerticalAlignment,
 };
 
 pub mod widget {
diff --git a/web/src/widget.rs b/web/src/widget.rs
index b0e16692..5cf0238a 100644
--- a/web/src/widget.rs
+++ b/web/src/widget.rs
@@ -25,6 +25,7 @@ pub mod text_input;
 mod checkbox;
 mod column;
 mod container;
+mod empty;
 mod image;
 mod radio;
 mod row;
@@ -44,6 +45,7 @@ pub use text_input::TextInput;
 pub use checkbox::Checkbox;
 pub use column::Column;
 pub use container::Container;
+pub use empty::Empty;
 pub use image::Image;
 pub use radio::Radio;
 pub use row::Row;
diff --git a/web/src/widget/empty.rs b/web/src/widget/empty.rs
new file mode 100644
index 00000000..dda17efe
--- /dev/null
+++ b/web/src/widget/empty.rs
@@ -0,0 +1,70 @@
+use crate::{style, Bus, Element, Length, Widget};
+use dodrio::bumpalo;
+
+/// An amount of empty space.
+///
+/// It can be useful if you want to fill some space with nothing.
+///
+/// [`Empty`]: struct.Empty.html
+#[derive(Debug)]
+pub struct Empty {
+    width: Length,
+    height: Length,
+}
+
+impl Empty {
+    /// Creates an amount of [`Empty`] space.
+    ///
+    /// [`Empty`]: struct.Empty.html
+    pub fn new() -> Self {
+        Empty {
+            width: Length::Shrink,
+            height: Length::Shrink,
+        }
+    }
+
+    /// Sets the width of the [`Empty`] space.
+    ///
+    /// [`Empty`]: struct..html
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Empty`] space.
+    ///
+    /// [`Empty`]: struct.Column.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+}
+
+impl<'a, Message> Widget<Message> for Empty {
+    fn node<'b>(
+        &self,
+        bump: &'b bumpalo::Bump,
+        _publish: &Bus<Message>,
+        _style_sheet: &mut style::Sheet<'b>,
+    ) -> dodrio::Node<'b> {
+        use dodrio::builder::*;
+
+        let width = style::length(self.width);
+        let height = style::length(self.height);
+
+        let style = bumpalo::format!(
+            in bump,
+            "width: {}; height: {};",
+            width,
+            height
+        );
+
+        div(bump).attr("style", style.into_bump_str()).finish()
+    }
+}
+
+impl<'a, Message> From<Empty> for Element<'a, Message> {
+    fn from(empty: Empty) -> Element<'a, Message> {
+        Element::new(empty)
+    }
+}
diff --git a/wgpu/src/renderer/widget.rs b/wgpu/src/renderer/widget.rs
index 91f107e8..f2d443fb 100644
--- a/wgpu/src/renderer/widget.rs
+++ b/wgpu/src/renderer/widget.rs
@@ -1,6 +1,7 @@
 mod button;
 mod checkbox;
 mod column;
+mod empty;
 mod image;
 mod radio;
 mod row;
diff --git a/wgpu/src/renderer/widget/empty.rs b/wgpu/src/renderer/widget/empty.rs
new file mode 100644
index 00000000..26ee74b4
--- /dev/null
+++ b/wgpu/src/renderer/widget/empty.rs
@@ -0,0 +1,8 @@
+use crate::{Primitive, Renderer};
+use iced_native::{empty, MouseCursor, Rectangle};
+
+impl empty::Renderer for Renderer {
+    fn draw(&mut self, _bounds: Rectangle) -> Self::Output {
+        (Primitive::None, MouseCursor::OutOfBounds)
+    }
+}