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use euclid::Size2D; use crate::{event::Event, unit::Cell, Printer}; /// A UI element pub trait View<T, M> { /// Draws this element fn draw(&self, printer: &Printer, focused: bool); /// Calculate the view's content-based size with minimum width /// /// This is not necessarily the view's *absolute* minimum width; in most /// cases that would end up being zero, which isn't useful. Instead, the /// value computed is a *sensible* minimum that, if [`draw`](View::draw) /// were called with this function's return value as the /// [`Printer`](crate::Printer)'s size, would produce a visually-acceptable /// result. /// /// # Examples /// /// The [`text`](crate::view::text) view finds the visual length of the /// [visually-longest](unicode_segmentation::UnicodeSegmentation::graphemes) /// sequence of [non-whitespace](std::str.split_whitespace) characters (or /// in other words, longest word including punctuation) and reports that /// length as its width. The height value is computed by /// [`textwrap`](textwrap)ing with that width and reporting the amount of /// lines it would take to display the text. fn width(&self) -> Size2D<u16, Cell>; /// Calculate the view's content-based size with minimum height /// /// This is not necessarily the view's *absolute* minimum height; in most /// cases that would end up being zero, which isn't useful. Instead, the /// value computed is a *sensible* minimum that, if [`draw`](View::draw) /// were called with this function's return value as the /// [`Printer`](crate::Printer)'s size, would produce a visually-acceptable /// result. /// /// # Examples /// /// The [`text`](crate::view::text) view reports its height as the number of /// lines in its content and its width as the visual length of the visually /// longest line. fn height(&self) -> Size2D<u16, Cell>; /// Given a constraint, calculate the size of this view fn layout(&self, constraint: Size2D<u16, Cell>) -> Size2D<u16, Cell>; /// Process an event and optionally produce messages fn event( &mut self, event: &Event<T>, focused: bool, ) -> Box<dyn Iterator<Item = M>>; /// Whether this element can be interacted with by the user /// /// Returning `false` from this method does not opt the implementor out of /// receiving events, only from acquiring focus. In other words, the /// `focused` argument to [`event()`] will be `false` after returning /// `false` from this function. Also, returning `true` doesn't imply that /// `focused` will be `true`, only that it may eventually be `true` when the /// user focuses this element. /// /// [`event()`]: View::event fn interactive(&self) -> bool; }