use crate::{input::mouse, Column, Element, Event, Layout, MouseCursor, Point};
use std::hash::Hasher;
use stretch::result;
/// A set of interactive graphical elements with a specific [`Layout`].
///
/// It can be updated and drawn.
///
/// Iced tries to avoid dictating how to write your event loop. You are in
/// charge of using this type in your system in any way you want.
///
/// [`Layout`]: struct.Layout.html
#[derive(Debug)]
pub struct UserInterface<'a, Message, Renderer> {
hash: u64,
root: Element<'a, Message, Renderer>,
layout: result::Layout,
cursor_position: Point,
}
impl<'a, Message, Renderer> UserInterface<'a, Message, Renderer> {
/// Builds a user interface for an [`Element`].
///
/// It is able to avoid expensive computations when using a [`Cache`]
/// obtained from a previous instance of a [`UserInterface`].
///
/// [`Element`]: struct.Element.html
/// [`Cache`]: struct.Cache.html
/// [`UserInterface`]: struct.UserInterface.html
///
/// # Example
/// Imagine we want to build a [`UserInterface`] for
/// [the counter example that we previously wrote](index.html#usage). Here
/// is naive way to set up our application loop:
///
/// ```no_run
/// use iced::{UserInterface, Cache};
/// use iced_wgpu::Renderer;
///
/// # mod iced_wgpu {
/// # pub struct Renderer;
/// #
/// # impl Renderer {
/// # pub fn new() -> Self { Renderer }
/// # }
/// # }
/// #
/// # use iced::Column;
/// #
/// # pub struct Counter;
/// #
/// # impl Counter {
/// # pub fn new() -> Self { Counter }
/// # pub fn view(&self) -> Column<(), Renderer> {
/// # Column::new()
/// # }
/// # }
/// // Initialization
/// let mut counter = Counter::new();
/// let mut cache = Cache::new();
/// let mut renderer = Renderer::new();
///
/// // Application loop
/// loop {
/// // Process system events here...
///
/// // Build the user interface
/// let user_interface = UserInterface::build(
/// counter.view(),
/// cache,
/// &renderer,
/// );
///
/// // Update and draw the user interface here...
/// // ...
///
/// // Obtain the cache for the next iteration
/// cache = user_interface.into_cache();
/// }
/// ```
pub fn build<E: Into<Element<'a, Message, Renderer>>>(
root: E,
cache: Cache,
renderer: &Renderer,
) -> Self {
let root = root.into();
let hasher = &mut crate::Hasher::default();
root.hash_layout(hasher);
let hash = hasher.finish();
let layout = if hash == cache.hash {
cache.layout
} else {
root.compute_layout(renderer)
};
UserInterface {
hash,
root,
layout,
cursor_position: cache.cursor_position,
}
}
/// Updates the [`UserInterface`] by processing each provided [`Event`].
///
/// It returns __messages__ that may have been produced as a result of user
/// interactions. You should feed these to your __update logic__.
///
/// [`UserInterface`]: struct.UserInterface.html
/// [`Event`]: enum.Event.html
///
/// # Example
/// Let's allow our [counter](index.html#usage) to change state by completing
/// [the previous example](#example):
///
/// ```no_run
/// use iced::{UserInterface, Cache};
/// use iced_wgpu::Renderer;
///
/// # mod iced_wgpu {
/// # pub struct Renderer;
/// #
/// # impl Renderer {
/// # pub fn new() -> Self { Renderer }
/// # }
/// # }
/// #
/// # use iced::Column;
/// #
/// # pub struct Counter;
/// #
/// # impl Counter {
/// # pub fn new() -> Self { Counter }
/// # pub fn view(&self) -> Column<(), Renderer> {
/// # Column::new()
/// # }
/// # pub fn update(&mut self, message: ()) {}
/// # }
/// let mut counter = Counter::new();
/// let mut cache = Cache::new();
/// let mut renderer = Renderer::new();
///
/// // Initialize our event storage
/// let mut events = Vec::new();
///
/// loop {
/// // Process system events...
///
/// let mut user_interface = UserInterface::build(
/// counter.view(),
/// cache,
/// &renderer,
/// );
///
/// // Update the user interface
/// let messages = user_interface.update(events.drain(..));
///
/// cache = user_interface.into_cache();
///
/// // Process the produced messages
/// for message in messages {
/// counter.update(message);
/// }
/// }
/// ```
pub fn update(
&mut self,
events: impl Iterator<Item = Event>,
) -> Vec<Message> {
let mut messages = Vec::new();
for event in events {
if let Event::Mouse(mouse::Event::CursorMoved { x, y }) = event {
self.cursor_position = Point::new(x, y);
}
self.root.widget.on_event(
event,
Layout::new(&self.layout),
self.cursor_position,
&mut messages,
);
}
messages
}
/// Draws the [`UserInterface`] with the provided [`Renderer`].
///
/// It returns the current state of the [`MouseCursor`]. You should update
/// the icon of the mouse cursor accordingly in your system.
///
/// [`UserInterface`]: struct.UserInterface.html
/// [`Renderer`]: trait.Renderer.html
/// [`MouseCursor`]: enum.MouseCursor.html
///
/// # Example
/// We can finally draw our [counter](index.html#usage) by
/// [completing the last example](#example-1):
///
/// ```no_run
/// use iced::{UserInterface, Cache};
/// use iced_wgpu::Renderer;
///
/// # mod iced_wgpu {
/// # pub struct Renderer;
/// #
/// # impl Renderer {
/// # pub fn new() -> Self { Renderer }
/// # }
/// # }
/// #
/// # use iced::Column;
/// #
/// # pub struct Counter;
/// #
/// # impl Counter {
/// # pub fn new() -> Self { Counter }
/// # pub fn view(&self) -> Column<(), Renderer> {
/// # Column::new()
/// # }
/// # pub fn update(&mut self, message: ()) {}
/// # }
/// let mut counter = Counter::new();
/// let mut cache = Cache::new();
/// let mut renderer = Renderer::new();
/// let mut events = Vec::new();
///
/// loop {
/// // Process system events...
///
/// let mut user_interface = UserInterface::build(
/// counter.view(),
/// cache,
/// &renderer,
/// );
///
/// let messages = user_interface.update(events.drain(..));
///
/// // Draw the user interface
/// let mouse_cursor = user_interface.draw(&mut renderer);
///
/// cache = user_interface.into_cache();
///
/// for message in messages {
/// counter.update(message);
/// }
///
/// // Update mouse cursor icon...
/// // Flush rendering operations...
/// }
/// ```
pub fn draw(&self, renderer: &mut Renderer) -> MouseCursor {
self.root.widget.draw(
renderer,
Layout::new(&self.layout),
self.cursor_position,
)
}
/// Extract the [`Cache`] of the [`UserInterface`], consuming it in the
/// process.
///
/// [`Cache`]: struct.Cache.html
/// [`UserInterface`]: struct.UserInterface.html
pub fn into_cache(self) -> Cache {
Cache {
hash: self.hash,
layout: self.layout,
cursor_position: self.cursor_position,
}
}
}
/// Reusable data of a specific [`UserInterface`].
///
/// [`UserInterface`]: struct.UserInterface.html
#[derive(Debug, Clone)]
pub struct Cache {
hash: u64,
layout: result::Layout,
cursor_position: Point,
}
impl Cache {
/// Creates an empty [`Cache`].
///
/// You should use this to initialize a [`Cache`] before building your first
/// [`UserInterface`].
///
/// [`Cache`]: struct.Cache.html
/// [`UserInterface`]: struct.UserInterface.html
pub fn new() -> Cache {
let root: Element<'_, (), ()> = Column::new().into();
let hasher = &mut crate::Hasher::default();
root.hash_layout(hasher);
Cache {
hash: hasher.finish(),
layout: root.compute_layout(&()),
cursor_position: Point::new(0.0, 0.0),
}
}
}
impl Default for Cache {
fn default() -> Cache {
Cache::new()
}
}
impl PartialEq for Cache {
fn eq(&self, other: &Cache) -> bool {
self.hash == other.hash && self.cursor_position == other.cursor_position
}
}
impl Eq for Cache {}