message: Improve `scroll` example
diff: use iced::{
  - button, scrollable, Align, Application, Button, Color, Column, Element,
  - Image, Justify, Length, Scrollable, Text,
  + button, scrollable, Align, Application, Button, Column, Element, Image,
  + Justify, Length, Scrollable, Text,
  };
  pub fn main() {
  @@ -9,7 +9,7 @@ pub fn main() {
  #[derive(Default)]
  struct Example {
  - paragraph_count: u16,
  + item_count: u16,
  scroll: scrollable::State,
  add_button: button::State,
  @@ -17,7 +17,7 @@ struct Example {
  #[derive(Debug, Clone, Copy)]
  pub enum Message {
  - AddParagraph,
  + AddItem,
  }
  impl Application for Example {
  @@ -25,37 +25,48 @@ impl Application for Example {
  fn update(&mut self, message: Message) {
  match message {
  - Message::AddParagraph => {
  - self.paragraph_count += 1;
  + Message::AddItem => {
  + self.item_count += 1;
  }
  }
  }
  fn view(&mut self) -> Element<Message> {
  - let content = (0..3).fold(
  - Scrollable::new(&mut self.scroll).spacing(20).padding(20),
  - |content, _| {
  - content.push(
  + //let content = (0..3).fold(
  + // Scrollable::new(&mut self.scroll).spacing(20).padding(20),
  + // |content, _| {
  + // content.push(
  + // )
  + // },
  + //);
  +
  + let content = (0..self.item_count)
  + .fold(
  + Scrollable::new(&mut self.scroll)
  + .spacing(20)
  + .padding(20)
  + .align_items(Align::Center),
  + |column, i| {
  + if i % 2 == 0 {
  + column.push(lorem_ipsum().width(Length::Units(600)))
  + } else {
  + column.push(
  Image::new(format!(
  "{}/examples/resources/ferris.png",
  env!("CARGO_MANIFEST_DIR")
  ))
  - .width(Length::Units(400))
  - .align_self(Align::Center),
  + .width(Length::Units(400)),
  )
  + }
  },
  + )
  + .push(
  + Button::new(&mut self.add_button, Text::new("Add item"))
  + .on_press(Message::AddItem)
  + .padding(20)
  + .border_radius(5),
  );
  - //let content = (0..self.paragraph_count)
  - // .fold(content, |column, _| column.push(lorem_ipsum()))
  - // .push(
  - // Button::new(&mut self.add_button, Text::new("Add paragraph"))
  - // .on_press(Message::AddParagraph)
  - // .padding(20)
  - // .border_radius(5)
  - // .align_self(Align::Center),
  - // );
  -
  Column::new()
  .height(Length::Fill)
  .justify_content(Justify::Center)
  