Move widgets from core to native and web

Also made fields private and improved `Renderer` traits.

native/src/widget/image.rs

@@ -1,10 +1,58 @@
 //! Display images in your user interface.
 
-use crate::{layout, Element, Hasher, Layout, Point, Widget};
+use crate::{layout, Element, Hasher, Layout, Length, Point, Size, Widget};
 
 use std::hash::Hash;
 
-pub use iced_core::Image;
+/// A frame that displays an image while keeping aspect ratio.
+///
+/// # Example
+///
+/// ```
+/// # use iced_native::Image;
+///
+/// let image = Image::new("resources/ferris.png");
+/// ```
+#[derive(Debug)]
+pub struct Image {
+    /// The image path
+    pub path: String,
+
+    /// The width of the image
+    pub width: Length,
+
+    /// The height of the image
+    pub height: Length,
+}
+
+impl Image {
+    /// Creates a new [`Image`] with the given path.
+    ///
+    /// [`Image`]: struct.Image.html
+    pub fn new<T: Into<String>>(path: T) -> Self {
+        Image {
+            path: path.into(),
+            width: Length::Shrink,
+            height: Length::Shrink,
+        }
+    }
+
+    /// Sets the width of the [`Image`] boundaries.
+    ///
+    /// [`Image`]: struct.Image.html
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Image`] boundaries.
+    ///
+    /// [`Image`]: struct.Image.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+}
 
 impl<Message, Renderer> Widget<Message, Renderer> for Image
 where
@@ -15,7 +63,26 @@ where
         renderer: &Renderer,
         limits: &layout::Limits,
     ) -> layout::Node {
-        renderer.layout(&self, limits)
+        let (width, height) = renderer.dimensions(&self.path);
+
+        let aspect_ratio = width as f32 / height as f32;
+
+        // TODO: Deal with additional cases
+        let (width, height) = match (self.width, self.height) {
+            (Length::Units(width), _) => (
+                self.width,
+                Length::Units((width as f32 / aspect_ratio).round() as u16),
+            ),
+            (_, _) => {
+                (Length::Units(width as u16), Length::Units(height as u16))
+            }
+        };
+
+        let mut size = limits.width(width).height(height).resolve(Size::ZERO);
+
+        size.height = size.width / aspect_ratio;
+
+        layout::Node::new(size)
     }
 
     fn draw(
@@ -41,13 +108,7 @@ where
 /// [`Image`]: struct.Image.html
 /// [renderer]: ../../renderer/index.html
 pub trait Renderer: crate::Renderer {
-    /// Creates a [`Node`] for the provided [`Image`].
-    ///
-    /// You should probably keep the original aspect ratio, if possible.
-    ///
-    /// [`Node`]: ../../struct.Node.html
-    /// [`Image`]: struct.Image.html
-    fn layout(&self, image: &Image, limits: &layout::Limits) -> layout::Node;
+    fn dimensions(&self, path: &str) -> (u32, u32);
 
     /// Draws an [`Image`].
     ///