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use stretch::{geometry, result};
use crate::graphics::{Color, Point};
use crate::ui::core::{self, Event, Hasher, Layout, MouseCursor, Node, Widget};
/// A generic [`Widget`].
///
/// If you have a widget, you should be able to use `widget.into()` to turn it
/// into an [`Element`].
///
/// [`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`]: 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.
///
/// [`Element`]: struct.Element.html
///
/// # Example
/// Let's say that we want to have a main menu and a gameplay overlay in our
/// game. We can decouple the interfaces nicely using modules and nested
/// messages:
///
/// ```
/// mod main_menu {
/// use coffee::ui::core::Element;
/// # use coffee::ui::Column;
/// use coffee::ui::Renderer;
///
/// pub struct MainMenu {
/// // Our main menu state here...
/// // Probably a bunch of `button::State` and other stuff.
/// }
///
/// #[derive(Debug, Clone, Copy)]
/// pub enum Message {
/// // The different interactions of the main menu here...
/// }
///
/// impl MainMenu {
/// // We probably would have our `update` function here too...
///
/// pub fn layout(&mut self) -> Element<Message, Renderer> {
/// // We show the main menu here...
/// // The returned `Element` produces `main_menu::Message`
/// # Column::new().into()
/// }
/// }
/// }
///
/// mod gameplay_overlay {
/// // Analogous to the `main_menu` module
/// # use coffee::ui::core::Element;
/// # use coffee::ui::Column;
/// # use coffee::ui::Renderer;
/// #
/// # pub struct GameplayOverlay { /* ... */ }
/// #
/// # #[derive(Debug, Clone, Copy)]
/// # pub enum Message { /* ... */ }
/// #
/// # impl GameplayOverlay {
/// # pub fn layout(&mut self) -> Element<Message, Renderer> {
/// # // ...
/// # Column::new().into()
/// # }
/// # }
/// }
///
/// use coffee::ui::core::Element;
/// use coffee::ui::Renderer;
/// use main_menu::MainMenu;
/// use gameplay_overlay::GameplayOverlay;
///
/// // The state of our UI
/// enum State {
/// MainMenu(MainMenu),
/// GameplayOverlay(GameplayOverlay),
/// // ...
/// }
///
/// // The messages of our UI
/// // We nest the messages here
/// #[derive(Debug, Clone, Copy)]
/// enum Message {
/// MainMenu(main_menu::Message),
/// GameplayOverlay(gameplay_overlay::Message),
/// // ...
/// }
///
/// // We show the UI here, transforming the local messages of each branch
/// // into the global `Message` type as needed.
/// pub fn layout(state: &mut State) -> Element<Message, Renderer> {
/// match state {
/// State::MainMenu(main_menu) => {
/// main_menu.layout().map(Message::MainMenu)
/// }
/// State::GameplayOverlay(gameplay_overlay) => {
/// gameplay_overlay.layout().map(Message::GameplayOverlay)
/// }
/// // ...
/// }
/// }
/// ```
///
/// This way, neither `main_menu` nor `gameplay_overlay` know anything about
/// the global `Message` type. They become reusable, allowing the user of
/// these modules to compose them together freely.
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: Color) -> Element<'a, Message, Renderer>
where
Message: 'static,
Renderer: 'a + core::Renderer,
{
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(&self, state: &mut Hasher) {
self.widget.hash(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(&self, state: &mut Hasher) {
self.widget.hash(state);
}
}
struct Explain<'a, Message, Renderer> {
element: Element<'a, Message, Renderer>,
color: Color,
}
impl<'a, Message, Renderer> std::fmt::Debug for Explain<'a, Message, Renderer> {
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> {
fn new(element: Element<'a, Message, Renderer>, color: Color) -> Self {
Explain { element, color }
}
}
impl<'a, Message, Renderer> Widget<Message, Renderer>
for Explain<'a, Message, Renderer>
where
Renderer: core::Renderer,
{
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(&self, state: &mut Hasher) {
self.element.widget.hash(state);
}
}