use stretch::{geometry, result};
use crate::{
renderer, Event, Hasher, Layout, MouseCursor, Node, Point, Widget,
};
/// A generic [`Widget`].
///
/// It is useful to build composable user interfaces that do not leak
/// implementation details in their __view logic__.
///
/// If you have a [built-in widget], you should be able to use `Into<Element>`
/// to turn it into an [`Element`].
///
/// [built-in widget]: widget/index.html#built-in-widgets
/// [`Widget`]: widget/trait.Widget.html
/// [`Element`]: struct.Element.html
pub struct Element<'a, Message, Renderer> {
pub(crate) widget: Box<dyn Widget<Message, Renderer> + 'a>,
}
impl<'a, Message, Renderer> std::fmt::Debug for Element<'a, Message, Renderer> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("Element")
.field("widget", &self.widget)
.finish()
}
}
impl<'a, Message, Renderer> Element<'a, Message, Renderer> {
/// Create a new [`Element`] containing the given [`Widget`].
///
/// [`Element`]: struct.Element.html
/// [`Widget`]: widget/trait.Widget.html
pub fn new(
widget: impl Widget<Message, Renderer> + 'a,
) -> Element<'a, Message, Renderer> {
Element {
widget: Box::new(widget),
}
}
/// Applies a transformation to the produced message of the [`Element`].
///
/// This method is useful when you want to decouple different parts of your
/// UI and make them __composable__.
///
/// [`Element`]: struct.Element.html
///
/// # Example
/// Imagine we want to use [our counter](index.html#usage). But instead of
/// showing a single counter, we want to display many of them. We can reuse
/// the `Counter` type as it is!
///
/// We use composition to model the __state__ of our new application:
///
/// ```
/// # mod counter {
/// # pub struct Counter;
/// # }
/// use counter::Counter;
///
/// struct ManyCounters {
/// counters: Vec<Counter>,
/// }
/// ```
///
/// We can store the state of multiple counters now. However, the
/// __messages__ we implemented before describe the user interactions
/// of a __single__ counter. Right now, we need to also identify which
/// counter is receiving user interactions. Can we use composition again?
/// Yes.
///
/// ```
/// # mod counter {
/// # #[derive(Debug, Clone, Copy)]
/// # pub enum Message {}
/// # }
/// #[derive(Debug, Clone, Copy)]
/// pub enum Message {
/// Counter(usize, counter::Message)
/// }
/// ```
///
/// We compose the previous __messages__ with the index of the counter
/// producing them. Let's implement our __view logic__ now:
///
/// ```
/// # mod counter {
/// # use iced::{button, Button};
/// #
/// # #[derive(Debug, Clone, Copy)]
/// # pub enum Message {}
/// # pub struct Counter(button::State);
/// #
/// # impl Counter {
/// # pub fn view(&mut self) -> Button<Message> {
/// # Button::new(&mut self.0, "_")
/// # }
/// # }
/// # }
/// #
/// # mod iced_wgpu {
/// # use iced::{
/// # button, MouseCursor, Node, Point, Rectangle, Style,
/// # };
/// # pub struct Renderer;
/// #
/// # impl button::Renderer for Renderer {
/// # fn draw(
/// # &mut self,
/// # _cursor_position: Point,
/// # _bounds: Rectangle,
/// # _state: &button::State,
/// # _label: &str,
/// # _class: button::Class,
/// # ) -> MouseCursor {
/// # MouseCursor::OutOfBounds
/// # }
/// # }
/// # }
/// #
/// # use counter::Counter;
/// #
/// # struct ManyCounters {
/// # counters: Vec<Counter>,
/// # }
/// #
/// # #[derive(Debug, Clone, Copy)]
/// # pub enum Message {
/// # Counter(usize, counter::Message)
/// # }
/// use iced::{Element, Row};
/// use iced_wgpu::Renderer;
///
/// impl ManyCounters {
/// pub fn view(&mut self) -> Row<Message, Renderer> {
/// // We can quickly populate a `Row` by folding over our counters
/// self.counters.iter_mut().enumerate().fold(
/// Row::new().spacing(20),
/// |row, (index, counter)| {
/// // We display the counter
/// let element: Element<counter::Message, Renderer> =
/// counter.view().into();
///
/// row.push(
/// // Here we turn our `Element<counter::Message>` into
/// // an `Element<Message>` by combining the `index` and the
/// // message of the `element`.
/// element.map(move |message| Message::Counter(index, message))
/// )
/// }
/// )
/// }
/// }
/// ```
///
/// Finally, our __update logic__ is pretty straightforward: simple
/// delegation.
///
/// ```
/// # mod counter {
/// # #[derive(Debug, Clone, Copy)]
/// # pub enum Message {}
/// # pub struct Counter;
/// #
/// # impl Counter {
/// # pub fn update(&mut self, _message: Message) {}
/// # }
/// # }
/// #
/// # use counter::Counter;
/// #
/// # struct ManyCounters {
/// # counters: Vec<Counter>,
/// # }
/// #
/// # #[derive(Debug, Clone, Copy)]
/// # pub enum Message {
/// # Counter(usize, counter::Message)
/// # }
/// impl ManyCounters {
/// pub fn update(&mut self, message: Message) {
/// match message {
/// Message::Counter(index, counter_msg) => {
/// if let Some(counter) = self.counters.get_mut(index) {
/// counter.update(counter_msg);
/// }
/// }
/// }
/// }
/// }
/// ```
pub fn map<F, B>(self, f: F) -> Element<'a, B, Renderer>
where
Message: 'static + Copy,
Renderer: 'a,
B: 'static,
F: 'static + Fn(Message) -> B,
{
Element {
widget: Box::new(Map::new(self.widget, f)),
}
}
/// Marks the [`Element`] as _to-be-explained_.
///
/// The [`Renderer`] will explain the layout of the [`Element`] graphically.
/// This can be very useful for debugging your layout!
///
/// [`Element`]: struct.Element.html
/// [`Renderer`]: trait.Renderer.html
pub fn explain(
self,
color: Renderer::Color,
) -> Element<'a, Message, Renderer>
where
Message: 'static,
Renderer: 'a + renderer::Debugger,
{
Element {
widget: Box::new(Explain::new(self, color)),
}
}
pub(crate) fn compute_layout(&self, renderer: &Renderer) -> result::Layout {
let node = self.widget.node(renderer);
node.0.compute_layout(geometry::Size::undefined()).unwrap()
}
pub(crate) fn hash_layout(&self, state: &mut Hasher) {
self.widget.hash_layout(state);
}
}
struct Map<'a, A, B, Renderer> {
widget: Box<dyn Widget<A, Renderer> + 'a>,
mapper: Box<dyn Fn(A) -> B>,
}
impl<'a, A, B, Renderer> std::fmt::Debug for Map<'a, A, B, Renderer> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("Map").field("widget", &self.widget).finish()
}
}
impl<'a, A, B, Renderer> Map<'a, A, B, Renderer> {
pub fn new<F>(
widget: Box<dyn Widget<A, Renderer> + 'a>,
mapper: F,
) -> Map<'a, A, B, Renderer>
where
F: 'static + Fn(A) -> B,
{
Map {
widget,
mapper: Box::new(mapper),
}
}
}
impl<'a, A, B, Renderer> Widget<B, Renderer> for Map<'a, A, B, Renderer>
where
A: Copy,
{
fn node(&self, renderer: &Renderer) -> Node {
self.widget.node(renderer)
}
fn on_event(
&mut self,
event: Event,
layout: Layout<'_>,
cursor_position: Point,
messages: &mut Vec<B>,
) {
let mut original_messages = Vec::new();
self.widget.on_event(
event,
layout,
cursor_position,
&mut original_messages,
);
original_messages
.iter()
.cloned()
.for_each(|message| messages.push((self.mapper)(message)));
}
fn draw(
&self,
renderer: &mut Renderer,
layout: Layout<'_>,
cursor_position: Point,
) -> MouseCursor {
self.widget.draw(renderer, layout, cursor_position)
}
fn hash_layout(&self, state: &mut Hasher) {
self.widget.hash_layout(state);
}
}
struct Explain<'a, Message, Renderer: renderer::Debugger> {
element: Element<'a, Message, Renderer>,
color: Renderer::Color,
}
impl<'a, Message, Renderer> std::fmt::Debug for Explain<'a, Message, Renderer>
where
Renderer: renderer::Debugger,
{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("Explain")
.field("element", &self.element)
.finish()
}
}
impl<'a, Message, Renderer> Explain<'a, Message, Renderer>
where
Renderer: renderer::Debugger,
{
fn new(
element: Element<'a, Message, Renderer>,
color: Renderer::Color,
) -> Self {
Explain { element, color }
}
}
impl<'a, Message, Renderer> Widget<Message, Renderer>
for Explain<'a, Message, Renderer>
where
Renderer: renderer::Debugger,
{
fn node(&self, renderer: &Renderer) -> Node {
self.element.widget.node(renderer)
}
fn on_event(
&mut self,
event: Event,
layout: Layout<'_>,
cursor_position: Point,
messages: &mut Vec<Message>,
) {
self.element
.widget
.on_event(event, layout, cursor_position, messages)
}
fn draw(
&self,
renderer: &mut Renderer,
layout: Layout<'_>,
cursor_position: Point,
) -> MouseCursor {
renderer.explain(&layout, self.color);
self.element.widget.draw(renderer, layout, cursor_position)
}
fn hash_layout(&self, state: &mut Hasher) {
self.element.widget.hash_layout(state);
}
}