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//! The async event loop that drives an [`Application`].
use crate::application::{Application, Subscription, Task};
use crate::dirty::DirtyRegion;
use crate::event::{ButtonState, InputEvent, Key, TouchPhase, UiAction};
use crate::focus::{FocusDirection, FocusState, WidgetId};
use crate::platform::Platform;
use crate::screen::ScreenView;
use crate::widget::Widget;
use alloc::vec::Vec;
use core::marker::PhantomData;
use embassy_futures::select::{Either3, select3};
use embedded_graphics::{prelude::*, primitives::Rectangle};
/// Drives an [`Application`]'s event loop on a [`Platform`].
pub struct Runtime<A: Application> {
_ph: PhantomData<A>,
}
impl<A: Application> Runtime<A> {
/// Create a runtime for application type `A`.
#[must_use]
pub fn new() -> Self {
Self { _ph: PhantomData }
}
/// Run the application event loop on `platform`: poll input, drive
/// `update` and subscriptions, and redraw on demand. Does not return.
pub async fn run<P>(self, mut platform: P)
where
P: Platform<Color = A::Color>,
{
let (mut app, initial_task) = A::init();
let mut viewport_size = platform.viewport();
let mut pending: Task<A::Message> = initial_task;
let mut subscription: Subscription<A::Message> = app.subscription();
let mut focus = FocusState::new();
let mut pressed_at: Option<Point> = None;
let mut dirty = DirtyRegion::full();
let capabilities = platform.capabilities();
loop {
let new_viewport = platform.viewport();
if new_viewport != viewport_size {
viewport_size = new_viewport;
dirty = DirtyRegion::full();
}
let viewport_rect = Rectangle::new(Point::zero(), viewport_size);
let msg_to_update = {
let screen = app.view();
let theme = screen.theme();
let mut elem = screen.view();
elem.arrange(viewport_rect);
let mut focus_order = Vec::new();
elem.collect_focusable(&mut focus_order);
focus.reconcile(&focus_order);
elem.sync_focus(focus.focused());
if let Some(p) = pressed_at {
elem.mark_pressed(p);
}
let bg = theme.background.base;
if !dirty.is_none() {
let _ = platform
.render_with_dirty(&dirty, |renderer| {
if capabilities.supports_clip
&& let Some(rects) = dirty.rects()
{
for rect in rects {
renderer.push_clip(*rect);
let _ = renderer.fill_rect(viewport_rect, bg);
let _ = elem.draw(renderer, theme);
renderer.pop_clip();
}
} else {
let _ = renderer.fill_rect(viewport_rect, bg);
let _ = elem.draw(renderer, theme);
}
Ok(())
})
.await;
}
dirty = DirtyRegion::none();
let outcome =
select3(platform.next_event(), pending.next(), subscription.next()).await;
let previous_focus = focus.focused();
match outcome {
Either3::First(None) => return,
Either3::First(Some(event)) => match event {
InputEvent::Touch(t) => {
if t.phase == TouchPhase::Down
&& let Some(target) = elem.focus_at(t.point)
{
focus.set(Some(target));
}
let m = elem.handle_touch(t.point, t.phase);
pressed_at = match t.phase {
TouchPhase::Down | TouchPhase::Moved => Some(t.point),
TouchPhase::Up => None,
};
dirty = DirtyRegion::full();
m
}
InputEvent::Key(key) => match (key.key, key.state) {
(Key::Tab, ButtonState::Pressed | ButtonState::Repeated) => {
focus.advance(&focus_order, FocusDirection::Forward);
dirty = Self::focus_dirty(&elem, previous_focus, focus.focused());
None
}
(Key::Escape, ButtonState::Pressed) => {
let msg =
Self::dispatch_action(&mut elem, &mut focus, UiAction::Cancel);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
(Key::Enter, ButtonState::Pressed) => {
let msg = Self::dispatch_action(
&mut elem,
&mut focus,
UiAction::Activate,
);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
(Key::Left, ButtonState::Pressed | ButtonState::Repeated) => {
let msg = Self::dispatch_action(
&mut elem,
&mut focus,
UiAction::NavigateLeft,
);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
(Key::Right, ButtonState::Pressed | ButtonState::Repeated) => {
let msg = Self::dispatch_action(
&mut elem,
&mut focus,
UiAction::NavigateRight,
);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
(Key::Up, ButtonState::Pressed | ButtonState::Repeated) => {
let msg = Self::dispatch_action(
&mut elem,
&mut focus,
UiAction::NavigateUp,
);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
(Key::Down, ButtonState::Pressed | ButtonState::Repeated) => {
let msg = Self::dispatch_action(
&mut elem,
&mut focus,
UiAction::NavigateDown,
);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
_ => None,
},
InputEvent::Encoder(encoder) => {
if encoder.delta > 0 {
focus.advance(&focus_order, FocusDirection::Forward);
} else if encoder.delta < 0 {
focus.advance(&focus_order, FocusDirection::Backward);
}
dirty = Self::focus_dirty(&elem, previous_focus, focus.focused());
None
}
InputEvent::Action(action) => match action {
UiAction::FocusNext => {
focus.advance(&focus_order, FocusDirection::Forward);
dirty = Self::focus_dirty(&elem, previous_focus, focus.focused());
None
}
UiAction::FocusPrevious => {
focus.advance(&focus_order, FocusDirection::Backward);
dirty = Self::focus_dirty(&elem, previous_focus, focus.focused());
None
}
UiAction::Cancel => {
let msg =
Self::dispatch_action(&mut elem, &mut focus, UiAction::Cancel);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
_ => {
let msg = Self::dispatch_action(&mut elem, &mut focus, action);
dirty = Self::dirty_after_action(
&elem,
previous_focus,
focus.focused(),
msg.is_some(),
);
msg
}
},
},
Either3::Second(m) => {
if m.is_some() {
dirty = DirtyRegion::full();
}
m
}
Either3::Third(m) => {
dirty = DirtyRegion::full();
Some(m)
}
}
};
if let Some(m) = msg_to_update {
let task = app.update(m);
pending.extend(task);
subscription.refresh(app.subscription());
dirty = DirtyRegion::full();
}
}
}
fn dispatch_action(
elem: &mut impl Widget<A::Color, A::Message>,
focus: &mut FocusState,
action: UiAction,
) -> Option<A::Message> {
let target = focus.focused()?;
if let Some(next) = elem.navigate_focus(target, action) {
focus.set(Some(next));
None
} else {
elem.route_action(target, action)
}
}
fn focus_dirty(
elem: &impl Widget<A::Color, A::Message>,
previous: Option<WidgetId>,
current: Option<WidgetId>,
) -> DirtyRegion {
if previous == current {
return DirtyRegion::none();
}
let mut dirty = DirtyRegion::none();
if let Some(target) = previous
&& let Some(rect) = elem.focus_rect(target)
{
dirty.add_rect(rect);
}
if let Some(target) = current
&& let Some(rect) = elem.focus_rect(target)
{
dirty.add_rect(rect);
}
if dirty.is_none() {
DirtyRegion::full()
} else {
dirty
}
}
fn dirty_after_action(
elem: &impl Widget<A::Color, A::Message>,
previous: Option<WidgetId>,
current: Option<WidgetId>,
emitted_message: bool,
) -> DirtyRegion {
if emitted_message {
DirtyRegion::full()
} else {
Self::focus_dirty(elem, previous, current)
}
}
}
impl<A: Application> Default for Runtime<A> {
fn default() -> Self {
Self::new()
}
}