Make tour work with iced_web again 🎉

- Implements `TextInput`, `Scrollable`, and `Container`
- Adds basic style generation

web/src/widget/scrollable.rs

@@ -0,0 +1,157 @@
+//! Navigate an endless amount of content with a scrollbar.
+use crate::{bumpalo, style, Align, Bus, Column, Element, Length, Widget};
+
+/// A widget that can vertically display an infinite amount of content with a
+/// scrollbar.
+#[allow(missing_debug_implementations)]
+pub struct Scrollable<'a, Message> {
+    width: Length,
+    height: Length,
+    max_height: u32,
+    content: Column<'a, Message>,
+}
+
+impl<'a, Message> Scrollable<'a, Message> {
+    /// Creates a new [`Scrollable`] with the given [`State`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    /// [`State`]: struct.State.html
+    pub fn new(_state: &'a mut State) -> Self {
+        use std::u32;
+
+        Scrollable {
+            width: Length::Fill,
+            height: Length::Shrink,
+            max_height: u32::MAX,
+            content: Column::new(),
+        }
+    }
+
+    /// Sets the vertical spacing _between_ elements.
+    ///
+    /// Custom margins per element do not exist in Iced. You should use this
+    /// method instead! While less flexible, it helps you keep spacing between
+    /// elements consistent.
+    pub fn spacing(mut self, units: u16) -> Self {
+        self.content = self.content.spacing(units);
+        self
+    }
+
+    /// Sets the padding of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn padding(mut self, units: u16) -> Self {
+        self.content = self.content.padding(units);
+        self
+    }
+
+    /// Sets the width of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn width(mut self, width: Length) -> Self {
+        self.width = width;
+        self
+    }
+
+    /// Sets the height of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn height(mut self, height: Length) -> Self {
+        self.height = height;
+        self
+    }
+
+    /// Sets the maximum width of the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn max_width(mut self, max_width: u32) -> Self {
+        self.content = self.content.max_width(max_width);
+        self
+    }
+
+    /// Sets the maximum height of the [`Scrollable`] in pixels.
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn max_height(mut self, max_height: u32) -> Self {
+        self.max_height = max_height;
+        self
+    }
+
+    /// Sets the horizontal alignment of the contents of the [`Scrollable`] .
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn align_items(mut self, align_items: Align) -> Self {
+        self.content = self.content.align_items(align_items);
+        self
+    }
+
+    /// Adds an element to the [`Scrollable`].
+    ///
+    /// [`Scrollable`]: struct.Scrollable.html
+    pub fn push<E>(mut self, child: E) -> Self
+    where
+        E: Into<Element<'a, Message>>,
+    {
+        self.content = self.content.push(child);
+        self
+    }
+}
+
+impl<'a, Message> Widget<Message> for Scrollable<'a, Message>
+where
+    Message: 'static,
+{
+    fn node<'b>(
+        &self,
+        bump: &'b bumpalo::Bump,
+        bus: &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 node = div(bump)
+            .attr(
+                "style",
+                bumpalo::format!(
+                    in bump,
+                    "width: {}; height: {}; max-height: {}px; overflow: auto",
+                    width,
+                    height,
+                    self.max_height
+                )
+                .into_bump_str(),
+            )
+            .children(vec![self.content.node(bump, bus, style_sheet)]);
+
+        // TODO: Complete styling
+
+        node.finish()
+    }
+}
+
+impl<'a, Message> From<Scrollable<'a, Message>> for Element<'a, Message>
+where
+    Message: 'static + Clone,
+{
+    fn from(scrollable: Scrollable<'a, Message>) -> Element<'a, Message> {
+        Element::new(scrollable)
+    }
+}
+
+/// The local state of a [`Scrollable`].
+///
+/// [`Scrollable`]: struct.Scrollable.html
+#[derive(Debug, Clone, Copy, Default)]
+pub struct State;
+
+impl State {
+    /// Creates a new [`State`] with the scrollbar located at the top.
+    ///
+    /// [`State`]: struct.State.html
+    pub fn new() -> Self {
+        State::default()
+    }
+}