Draft `Panes` widget and `panes` example

4 files changed, 243 insertions, 2 deletions

diff --git a/native/src/element.rs b/native/src/element.rs
index 276f7614..4e7c7fc6 100644
--- a/native/src/element.rs
+++ b/native/src/element.rs
@@ -243,7 +243,7 @@ where
     }
 
     /// Computes the _layout_ hash of the [`Element`].
-    /// 
+    ///
     /// [`Element`]: struct.Element.html
     pub fn hash_layout(&self, state: &mut Hasher) {
         self.widget.hash_layout(state);
diff --git a/native/src/lib.rs b/native/src/lib.rs
index e4e7baee..4551a982 100644
--- a/native/src/lib.rs
+++ b/native/src/lib.rs
@@ -34,7 +34,7 @@
 //! [`window::Renderer`]: window/trait.Renderer.html
 //! [`UserInterface`]: struct.UserInterface.html
 //! [renderer]: renderer/index.html
-#![deny(missing_docs)]
+//#![deny(missing_docs)]
 #![deny(missing_debug_implementations)]
 #![deny(unused_results)]
 #![forbid(unsafe_code)]
diff --git a/native/src/widget.rs b/native/src/widget.rs
index f9424b02..d97e836c 100644
--- a/native/src/widget.rs
+++ b/native/src/widget.rs
@@ -25,6 +25,7 @@ pub mod checkbox;
 pub mod column;
 pub mod container;
 pub mod image;
+pub mod panes;
 pub mod progress_bar;
 pub mod radio;
 pub mod row;
@@ -46,6 +47,8 @@ pub use container::Container;
 #[doc(no_inline)]
 pub use image::Image;
 #[doc(no_inline)]
+pub use panes::Panes;
+#[doc(no_inline)]
 pub use progress_bar::ProgressBar;
 #[doc(no_inline)]
 pub use radio::Radio;
diff --git a/native/src/widget/panes.rs b/native/src/widget/panes.rs
new file mode 100644
index 00000000..d69d251e
--- /dev/null
+++ b/native/src/widget/panes.rs
@@ -0,0 +1,238 @@
+use crate::{
+    layout, Clipboard, Element, Event, Hasher, Layout, Length, Point, Size,
+    Widget,
+};
+
+use std::collections::HashMap;
+
+#[allow(missing_debug_implementations)]
+pub struct Panes<'a, Message, Renderer> {
+    state: &'a mut Internal,
+    elements: Vec<Element<'a, Message, Renderer>>,
+    width: Length,
+    height: Length,
+}
+
+impl<'a, Message, Renderer> Panes<'a, Message, Renderer> {
+    pub fn new<T>(
+        state: &'a mut State<T>,
+        view: impl Fn(Pane, &'a mut T) -> Element<'a, Message, Renderer>,
+    ) -> Self {
+        let elements = state
+            .panes
+            .iter_mut()
+            .map(|(pane, state)| view(*pane, state))
+            .collect();
+
+        Self {
+            state: &mut state.internal,
+            elements,
+            width: Length::Fill,
+            height: Length::Fill,
+        }
+    }
+
+    /// Sets the width of the [`Panes`].
+    ///
+    /// [`Panes`]: struct.Column.html
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Panes`].
+    ///
+    /// [`Panes`]: struct.Column.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+}
+
+impl<'a, Message, Renderer> Widget<Message, Renderer>
+    for Panes<'a, Message, Renderer>
+where
+    Renderer: self::Renderer + 'static,
+    Message: 'static,
+{
+    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);
+        let size = limits.resolve(Size::ZERO);
+
+        let children = self
+            .elements
+            .iter()
+            .map(|element| element.layout(renderer, &limits))
+            .collect();
+
+        layout::Node::with_children(size, children)
+    }
+
+    fn draw(
+        &self,
+        renderer: &mut Renderer,
+        defaults: &Renderer::Defaults,
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Renderer::Output {
+        renderer.draw(defaults, &self.elements, layout, cursor_position)
+    }
+
+    fn hash_layout(&self, state: &mut Hasher) {
+        use std::hash::Hash;
+
+        std::any::TypeId::of::<Panes<'_, Message, Renderer>>().hash(state);
+        self.width.hash(state);
+        self.height.hash(state);
+        self.state.layout.hash(state);
+
+        for element in &self.elements {
+            element.hash_layout(state);
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Pane(usize);
+
+#[derive(Debug)]
+pub struct State<T> {
+    panes: HashMap<Pane, T>,
+    internal: Internal,
+}
+
+#[derive(Debug)]
+struct Internal {
+    layout: Node,
+    last_pane: usize,
+    focused_pane: Option<Pane>,
+}
+
+impl<T> State<T> {
+    pub fn new(first_pane_state: T) -> (Self, Pane) {
+        let first_pane = Pane(0);
+
+        let mut panes = HashMap::new();
+        let _ = panes.insert(first_pane, first_pane_state);
+
+        (
+            State {
+                panes,
+                internal: Internal {
+                    layout: Node::Pane(first_pane),
+                    last_pane: 0,
+                    focused_pane: None,
+                },
+            },
+            first_pane,
+        )
+    }
+
+    pub fn get_mut(&mut self, pane: &Pane) -> Option<&mut T> {
+        self.panes.get_mut(pane)
+    }
+
+    pub fn iter(&self) -> impl Iterator<Item = (Pane, &T)> {
+        self.panes.iter().map(|(pane, state)| (*pane, state))
+    }
+
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (Pane, &mut T)> {
+        self.panes.iter_mut().map(|(pane, state)| (*pane, state))
+    }
+
+    pub fn focused_pane(&self) -> Option<Pane> {
+        self.internal.focused_pane
+    }
+
+    pub fn focus(&mut self, pane: Pane) {
+        self.internal.focused_pane = Some(pane);
+    }
+
+    pub fn split_vertically(&mut self, pane: &Pane, state: T) -> Option<Pane> {
+        let new_pane = Pane(self.internal.last_pane.checked_add(1)?);
+
+        // TODO
+
+        Some(new_pane)
+    }
+
+    pub fn split_horizontally(
+        &mut self,
+        pane: &Pane,
+        state: T,
+    ) -> Option<Pane> {
+        let new_pane = Pane(self.internal.last_pane.checked_add(1)?);
+
+        // TODO
+
+        Some(new_pane)
+    }
+}
+
+#[derive(Debug, Clone, Hash)]
+enum Node {
+    Split {
+        kind: Split,
+        ratio: u32,
+        a: Box<Node>,
+        b: Box<Node>,
+    },
+    Pane(Pane),
+}
+
+#[derive(Debug, Clone, Copy, Hash)]
+enum Split {
+    Horizontal,
+    Vertical,
+}
+
+/// The renderer of some [`Panes`].
+///
+/// Your [renderer] will need to implement this trait before being
+/// able to use [`Panes`] in your user interface.
+///
+/// [`Panes`]: struct.Panes.html
+/// [renderer]: ../../renderer/index.html
+pub trait Renderer: crate::Renderer + Sized {
+    /// Draws some [`Panes`].
+    ///
+    /// It receives:
+    /// - the children of the [`Column`]
+    /// - the [`Layout`] of the [`Column`] and its children
+    /// - the cursor position
+    ///
+    /// [`Column`]: struct.Row.html
+    /// [`Layout`]: ../layout/struct.Layout.html
+    fn draw<Message>(
+        &mut self,
+        defaults: &Self::Defaults,
+        content: &[Element<'_, Message, Self>],
+        layout: Layout<'_>,
+        cursor_position: Point,
+    ) -> Self::Output;
+}
+
+impl<'a, Message, Renderer> From<Panes<'a, Message, Renderer>>
+    for Element<'a, Message, Renderer>
+where
+    Renderer: self::Renderer + 'static,
+    Message: 'static,
+{
+    fn from(
+        panes: Panes<'a, Message, Renderer>,
+    ) -> Element<'a, Message, Renderer> {
+        Element::new(panes)
+    }
+}