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use crate::direction::Direction;
use crate::event::{AnyCb, Event, EventResult};
use crate::rect::Rect;
use crate::view::{AnyView, Selector};
use crate::Printer;
use crate::Vec2;
use std::any::Any;
/// Main trait defining a view behaviour.
///
/// This is what you should implement to define a custom View.
pub trait View: Any + AnyView {
/// Draws the view with the given printer (includes bounds) and focus.
///
/// This is the only *required* method to implement.
fn draw(&self, printer: &Printer<'_, '_>);
/// Called once the size for this view has been decided.
///
/// It can be used to pre-compute the configuration of child views.
///
/// View groups should propagate the information to their children.
///
/// At this point, the given size is final and cannot be negociated.
/// It is guaranteed to be the size available for the call to `draw()`.
fn layout(&mut self, _: Vec2) {}
/// Should return `true` if the view content changed since the last call
/// to `layout()`.
///
/// This is mostly an optimisation for views where the layout phase is
/// expensive.
///
/// * Views can ignore it and always return true (default implementation).
/// They will always be assumed to have changed.
/// * View Groups can ignore it and always re-layout their children.
/// * If they call `required_size` or `layout` with stable parameters,
/// the children may cache the result themselves and speed up the
/// process anyway.
fn needs_relayout(&self) -> bool {
true
}
/// Returns the minimum size the view requires with the given restrictions.
///
/// This is the main way a view communicate its size to its parent.
///
/// Some views have a fixed size, and will ignore the `constraint`
/// parameter entirely.
///
/// Some views are flexible, and may adapt fully or partially to the
/// constraints.
///
/// Default implementation always return `(1,1)`.
fn required_size(&mut self, constraint: Vec2) -> Vec2 {
let _ = constraint;
Vec2::new(1, 1)
}
/// Called when an event is received (key press, mouse event, ...).
///
/// You can return an `EventResult`:
/// * `EventResult::Ignored` means the event was not processed and may be
/// sent to another view.
/// * `EventResult::Consumed` means the event was consumed and should not
/// be sent to any other view. It may in addition include a callback
/// to be run.
///
/// The default implementation just ignores any event.
fn on_event(&mut self, _: Event) -> EventResult {
EventResult::Ignored
}
/// Runs a closure on the view identified by the given selector.
///
/// See [`Finder::call_on`] for a nicer interface, implemented for all
/// views.
///
/// [`Finder::call_on`]: crate::view::Finder::call_on
///
/// If the selector doesn't find a match, the closure will not be run.
///
/// View groups should implement this to forward the call to each children.
///
/// Default implementation is a no-op.
fn call_on_any<'a>(&mut self, _: &Selector<'_>, _: AnyCb<'a>) {
// TODO: FnMut -> FnOnce once it works
}
/// Moves the focus to the view identified by the given selector.
///
/// Returns `Ok(())` if the view was found and selected.
///
/// Default implementation simply returns `Err(())`.
fn focus_view(&mut self, _: &Selector<'_>) -> Result<(), ()> {
Err(())
}
/// This view is offered focus. Will it take it?
///
/// `source` indicates where the focus comes from.
/// When the source is unclear, `Front` is usually used.
///
/// Default implementation always return `false`.
fn take_focus(&mut self, source: Direction) -> bool {
let _ = source;
false
}
/// What part of the view is important and should be visible?
///
/// When only part of this view can be visible, this helps
/// determine which part.
///
/// It is given the view size (same size given to `layout`).
///
/// Default implementation return the entire view.
fn important_area(&self, view_size: Vec2) -> Rect {
Rect::from_size((0, 0), view_size)
}
}