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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); } }