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use crate::canvas::event::{self, Event};
use crate::canvas::mouse;
use crate::core::Rectangle;
use crate::graphics::geometry;
/// The state and logic of a [`Canvas`].
///
/// A [`Program`] can mutate internal state and produce messages for an
/// application.
///
/// [`Canvas`]: crate::Canvas
pub trait Program<Message, Renderer = crate::Renderer>
where
Renderer: geometry::Renderer,
{
/// The internal state mutated by the [`Program`].
type State: Default + 'static;
/// Updates the [`State`](Self::State) of the [`Program`].
///
/// When a [`Program`] is used in a [`Canvas`], the runtime will call this
/// method for each [`Event`].
///
/// This method can optionally return a `Message` to notify an application
/// of any meaningful interactions.
///
/// By default, this method does and returns nothing.
///
/// [`Canvas`]: crate::Canvas
fn update(
&self,
_state: &mut Self::State,
_event: Event,
_bounds: Rectangle,
_cursor: mouse::Cursor,
) -> (event::Status, Option<Message>) {
(event::Status::Ignored, None)
}
/// Draws the state of the [`Program`], producing a bunch of [`Geometry`].
///
/// [`Geometry`] can be easily generated with a [`Frame`] or stored in a
/// [`Cache`].
///
/// [`Geometry`]: crate::canvas::Geometry
/// [`Frame`]: crate::canvas::Frame
/// [`Cache`]: crate::canvas::Cache
fn draw(
&self,
state: &Self::State,
renderer: &Renderer,
theme: &Renderer::Theme,
bounds: Rectangle,
cursor: mouse::Cursor,
) -> Vec<Renderer::Geometry>;
/// Returns the current mouse interaction of the [`Program`].
///
/// The interaction returned will be in effect even if the cursor position
/// is out of bounds of the program's [`Canvas`].
///
/// [`Canvas`]: crate::Canvas
fn mouse_interaction(
&self,
_state: &Self::State,
_bounds: Rectangle,
_cursor: mouse::Cursor,
) -> mouse::Interaction {
mouse::Interaction::default()
}
}
impl<Message, Renderer, T> Program<Message, Renderer> for &T
where
Renderer: geometry::Renderer,
T: Program<Message, Renderer>,
{
type State = T::State;
fn update(
&self,
state: &mut Self::State,
event: Event,
bounds: Rectangle,
cursor: mouse::Cursor,
) -> (event::Status, Option<Message>) {
T::update(self, state, event, bounds, cursor)
}
fn draw(
&self,
state: &Self::State,
renderer: &Renderer,
theme: &Renderer::Theme,
bounds: Rectangle,
cursor: mouse::Cursor,
) -> Vec<Renderer::Geometry> {
T::draw(self, state, renderer, theme, bounds, cursor)
}
fn mouse_interaction(
&self,
state: &Self::State,
bounds: Rectangle,
cursor: mouse::Cursor,
) -> mouse::Interaction {
T::mouse_interaction(self, state, bounds, cursor)
}
}
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